A magnetic memory cell structure

Abstract

The application relates to the field of magnetic storage, in particular to a magnetic storage unit structure. The application replaces the [ferromagnetic / non-magnetic layer]n multilayer coupling structure or the ferromagnetic layer / antiferromagnetic layer structure commonly used in the current SOT-MRAM core storage unit with the exchange bias interlayer structure ferromagnetic layer / ultra-thin metal interlayer / antiferromagnetic layer structure. Through the addition of the ultra-thin metal interlayer, the ferromagnetic and antiferromagnetic interface magnetic moments can be controlled by changing the interlayer metal material and its thickness, so that the coexistence of in-plane and out-of-plane exchange bias in the exchange bias structure is realized. Meanwhile, for storage, the out-of-plane exchange bias field is used to ensure the stability of the fixed layer of the storage unit, and the in-plane exchange bias field is used as the replacement of the required in-plane lateral field, so that the low-power consumption flipping of the information storage layer is realized without increasing the lateral magnetic field providing circuit, and the purpose of reducing the overall structure complexity is achieved.

Description

Technical Field

[0001] This invention relates to the field of magnetic storage, specifically to a magnetic storage cell structure, which involves realizing magnetic storage using an in-plane and out-of-plane coexisting exchange bias structure. Background Technology

[0002] Spin-orbit torque magnetic random access memory (SOT-MRAM) utilizes materials with strong spin-orbit coupling effects (such as Pt, W, and Ta) as write lines, injecting charge currents to modulate the magnetic moment orientation of the free layer (information storage layer) of the magnetic tunnel junction. Its structure is as follows: Figure 2 As shown, the magnetic moment of the free layer flips due to the transverse spin current generated by the spin Hall effect (SHE) as the injected charge is transported in the write line; while the fixed layer (information storage reference layer) generally adopts a multi-layer coupling structure of [ferromagnetic / non-magnetic layers] n, or a direct exchange bias structure of ferromagnetic / antiferromagnetic layers; its magnetic moment remains unchanged under the action of the write current. The high and low resistance states obtained by the parallel or antiparallel orientation of the free layer and the fixed layer are used to realize the writing and storage of binary information "0" and "1" in the tunnel junction.

[0003] In SOT-MRAM, vertical magnetic anisotropic tunnel junctions are widely used due to their advantages such as higher thermal stability and storage density. However, when the vertical magnetic moment is flipped based on spin-orbit torque, an in-plane transverse magnetic field is required to break the symmetry of the magnetic thin film flipping, thereby achieving deterministic flipping of the vertical magnetic moment in the free layer. Currently, this in-plane transverse magnetic field is generally introduced by generating a magnetic field from the current in the conductor near the free layer side of the magnetic tunnel junction. This not only increases the structural complexity of the entire memory cell, but also increases the power consumption of the entire device due to the in-plane transverse magnetic field generated by the current, which is not conducive to improving the storage density and reducing the power consumption of the device.

[0004] Therefore, realizing SOT-MRAM without the need for an in-plane transverse magnetic field is one of the main directions of development for this type of memory. Summary of the Invention

[0005] To address the aforementioned problems or shortcomings, this invention provides a magnetic storage cell structure (such as...). Figure 1As shown, in existing vertical anisotropic tunnel junction memory cells, an intercalation-switched bias structure is used to replace the commonly used multilayer coupled memory fixed layer or direct switching bias structure. This structure is a SOT-MRAM structure that can be realized without an in-plane lateral magnetic field. By using the coexistence of in-plane and out-of-plane switching biases in the intercalation-switched bias structure, the stability of the memory cell fixed layer is ensured by the out-of-plane switching bias field, and the in-plane switching bias field is used as a substitute for the required in-plane lateral magnetic field. Low-power switching of the memory cell can be achieved without adding a lateral magnetic field providing circuit.

[0006] A magnetic storage cell structure, namely a SOT-MRAM structure, wherein the SOT-MRAM structure comprises, from bottom to top: a write track layer 1, a vertical magnetic anisotropic tunnel junction 2, and a protective layer 3.

[0007] The writing track layer 1 is composed of a heavy metal material with a spin Hall angle greater than 0.1, and also serves as the bottom electrode when reading information from the magnetic storage unit.

[0008] The vertical magnetic anisotropic tunnel junction 2 includes an information storage layer 201, a tunneling layer 202, and an information storage reference layer 203 stacked sequentially from bottom to top.

[0009] The information storage layer 201 is made of magnetic material; the information storage reference layer 203 is composed of ferromagnetic layer / ultra-thin metal intercalation layer / antiferromagnetic layer stacked from bottom to top. The orientation of the magnetic moment at the interface between the ferromagnetic layer and the antiferromagnetic layer is adjusted by the insertion of the ultra-thin metal intercalation layer, so as to achieve the coexistence of in-plane and out-of-plane exchange bias fields.

[0010] The ferromagnetic layer in the information storage layer 201 and the information storage reference layer 203 has a thickness of 0.8-1.5 nm to achieve out-of-plane orientation of the magnetic moment of the layer; the ultrathin metal intercalation layer has a thickness of 0.2-1.0 nm, and the magnitude of the in-plane and out-of-plane exchange bias field can be controlled by adjusting its material type and thickness to meet the needs of different applications.

[0011] The protective layer 3 completely covers the information storage reference layer 203, which is used to protect the core vertical magnetic anisotropic tunnel junction 2 and to serve as the top electrode when reading magnetic storage information.

[0012] Preferably, the material written into the orbital layer 1 is Pt, W, or Ta.

[0013] Preferably, the material of the information storage layer 201 is CoFeB, Fe, or Co.

[0014] Preferably, the material of the tunneling layer 202 is MgO or Al2O3.

[0015] Preferably, in the information storage reference layer 203: the ferromagnetic layer material is the same as that of the information storage layer 201; the material of the ultrathin metal intercalation layer is Pt, Ta, or Cu; and the material of the antiferromagnetic layer is IrMn or PtMn.

[0016] Preferably, the material of the protective layer 3 is Ta.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] This invention replaces the commonly used [ferromagnetic / nonmagnetic layer] n multilayer coupling structure or ferromagnetic layer / antiferromagnetic layer structure in the core memory cell of SOT-MRAM with a ferromagnetic layer / ultrathin metal intercalation / antiferromagnetic layer structure. By adding an ultrathin metal intercalation layer, the magnetic moment of the ferromagnetic and antiferromagnetic interface can be controlled by varying the selected intercalation metal material and its thickness, achieving the coexistence of in-plane and out-of-plane exchange bias in the exchange bias structure. At the same time, for storage, the out-of-plane exchange bias field ensures the stability of the fixed layer of the memory cell, and the in-plane exchange bias field replaces the required in-plane lateral field. This allows for the flipping of the information storage layer without increasing the circuitry for the lateral magnetic field, thereby reducing the overall structural complexity. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the SOT-MRAM magnetic storage cell structure of the present invention.

[0020] Figure 2 This is a schematic diagram of the structure of a comparative magnetic storage unit.

[0021] Figure 3 This is a schematic diagram illustrating how the resistance of the magnetic storage cell changes with the current density in the embodiment.

[0022] Figure 4 This is a schematic diagram illustrating how the resistance of a comparative magnetic storage cell changes with the magnitude of current density.

[0023] Reference numerals: 1-Write track layer, 2-Vertical magnetic anisotropic tunnel junction, 201-Information storage layer, 202-Tunneling layer, 203-Information storage reference layer, 203(1)-Ferromagnetic layer, 203(2)-Ultra-thin metal intercalation layer, 203(3)-Antiferromagnetic layer; 3-Protective layer. Detailed Implementation

[0024] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings, embodiments and comparative examples.

[0025] Example

[0026] A magnetic memory cell structure was deposited on a Si / SiO2 substrate, consisting of Pt (3nm) / CoFeB (1.2nm) / MgO (1.5nm) / CoFeB (1.2nm) / Pt (0.5nm) / IrMn (5nm) / Ta (10nm). The write orbital layer is 10μm wide and 150μm long; the entire magnetic memory cell is a rectangular cell 10μm wide and 15μm long. A schematic diagram of this structure is shown below. Figure 1 As shown. After fabrication, a test current was injected along end A of the written track layer 1, starting from zero, gradually increasing, then decreasing, then increasing again in the opposite direction and finally decreasing to zero. Simultaneously, the resistance between the top electrode (i.e., the protective layer) and the bottom electrode (i.e., end B of track layer 1) of the magnetic storage cell was measured. The test results are shown below. Figure 3 As shown, when the forward write current reaches about 18mA, the magnetic storage cell resistance decreases from about 780Ω to about 540Ω, while when the reverse write current reaches about 18mA, the magnetic storage cell resistance rises back from about 540Ω to 780Ω. This test was completed without an external in-plane auxiliary magnetic field, that is, magnetic field-free driving flipping was achieved.

[0027] Comparative Example

[0028] For reference, a magnetic storage cell structure (with only the ultrathin metal intercalation layer removed) was deposited on a Si / SiO2 substrate: Pt (3nm) / CoFeB (1.2nm) / MgO (1.5nm) / CoFeB (1.2nm) / IrMn (5nm) / Ta (10nm). The structure is as follows: Figure 2 As shown, the information storage reference layer 203 includes a ferromagnetic layer 203(1) and an antiferromagnetic layer 203(3). The test method is consistent with the embodiment, and the test results are as follows. Figure 4 As shown, Figure 4 This is a schematic diagram illustrating the change in resistance as a function of current density for a comparative example (an existing SOT-MRAM magnetic memory cell without ultra-thin metal intercalation). As can be seen from the test diagram, for a magnetic memory cell without ultra-thin metal intercalation, without an external transverse magnetic field, the magnetic moment cannot be flipped using the drive current of the write track layer; that is, the writing of 0 and 1 signals to the magnetic memory cell cannot be completed. However, when a transverse field of 500 Oe is applied along the write track layer direction, as shown in the test diagram, a write current of approximately 18 mA can drive the magnetic moment of the information storage layer, enabling the writing of 0 and 1 signals.

[0029] As can be seen from the above embodiments and comparative examples, the present invention replaces the commonly used [ferromagnetic / non-magnetic layer] n multilayer coupling structure or ferromagnetic layer / antiferromagnetic layer structure of the current SOT-MRAM core memory cell with a ferromagnetic layer / ultra-thin metal intercalation / antiferromagnetic layer structure with a swapped bias intercalation structure. By adding an ultra-thin metal intercalation layer, the magnetic moment of the ferromagnetic and antiferromagnetic interface can be controlled by changing the selected intercalation metal material and its thickness, so as to achieve the coexistence of in-plane and out-of-plane swapped bias in the swapped bias structure. At the same time, for storage, the out-of-plane swapped bias field ensures the stability of the fixed layer of the memory cell, and the in-plane swapped bias field replaces the required in-plane lateral field. Low-power switching of the information storage layer can be achieved without increasing the circuit for providing the lateral magnetic field, thereby reducing the overall structural complexity.

Claims

1. A magnetic storage cell structure, which is a SOT-MRAM structure, comprising, from bottom to top, a write track layer 1, a perpendicular magnetic anisotropic tunnel junction 2, and a protective layer 3, characterized in that: The writing track layer 1 is composed of a heavy metal material with a spin Hall angle greater than 0.1, and also serves as the bottom electrode when reading information from the magnetic storage unit. The vertical magnetic anisotropic tunnel junction 2 includes an information storage layer 201, a tunneling layer 202 and an information storage reference layer 203 stacked from bottom to top; The information storage layer 201 is made of magnetic material; the information storage reference layer 203 is composed of ferromagnetic layer / ultra-thin metal intercalation layer / antiferromagnetic layer stacked from bottom to top. The orientation of the magnetic moment at the interface between the ferromagnetic layer and the antiferromagnetic layer is adjusted by the insertion of the ultra-thin metal intercalation layer, so as to achieve the coexistence of in-plane and out-of-plane exchange bias fields. The ferromagnetic layer in the information storage layer 201 and the information storage reference layer 203 has a thickness of 0.8-1.5 nm to achieve out-of-plane orientation of the magnetic moment; the ultrathin metal intercalation layer has a thickness of 0.2-1.0 nm; in the information storage reference layer 203, the ferromagnetic layer material is the same as that in the information storage layer 201. The protective layer 3 completely covers the information storage reference layer 203, which is used to protect the vertical magnetic anisotropic tunnel junction 2 and to serve as the top electrode when reading magnetic storage information.

2. The magnetic storage cell structure as described in claim 1, characterized in that: The material written into orbital layer 1 is Pt, W, or Ta.

3. The magnetic storage cell structure as described in claim 1, characterized in that: The material of the information storage layer 201 is CoFeB, Fe, or Co.

4. The magnetic storage cell structure as described in claim 1, characterized in that: The material of the tunneling layer 202 is MgO or Al2O3.

5. The magnetic storage cell structure as described in claim 1, characterized in that: The ultrathin metal intercalation layer is made of Pt, Ta, or Cu. The magnitude of the in-plane and out-of-plane exchange bias field can be controlled by adjusting the material type and thickness to meet the needs of different applications. The antiferromagnetic layer is made of IrMn or PtMn.

6. The magnetic storage cell structure as described in claim 1, characterized in that: The material of the protective layer 3 is Ta.

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