CN114141944B - Magnetic random access memory based on wedge-shaped cobalt-platinum component gradient film and preparation method thereof - Google Patents
Magnetic random access memory based on wedge-shaped cobalt-platinum component gradient film and preparation method thereof Download PDFInfo
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- CN114141944B CN114141944B CN202111445677.2A CN202111445677A CN114141944B CN 114141944 B CN114141944 B CN 114141944B CN 202111445677 A CN202111445677 A CN 202111445677A CN 114141944 B CN114141944 B CN 114141944B
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- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
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- H—ELECTRICITY
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- H—ELECTRICITY
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- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D10/00—Energy efficient computing, e.g. low power processors, power management or thermal management
Abstract
The invention discloses a magnetic random access memory based on a wedge-shaped cobalt-platinum component gradient film and a preparation method thereof. The invention comprises a protective layer, a film layer and a buffer layer in turn from top to bottom, and electrodes are arranged on the periphery. The structure formed by etching the protective layer, the film layer and the buffer layer is a cross structure, the film layer is composed of a Pt, co, pt, co, pt, co, mgO structure from bottom to top, and the Pt at the lowest layer and the Co at the uppermost layer are wedge structures. And in the regulating current Is which Is introduced along the direction perpendicular to the change direction of the wedge-shaped layer, the other two electrodes of the device detect the change of the resistance value of the thin film layer, and when pulse current in the same direction Is continuously introduced, the resistance Is continuously changed to an extreme value. The invention can realize high-efficiency storage through current regulation and control.
Description
Technical Field
The invention belongs to the field of magnetic random access memories, and particularly relates to a magnetic random access memory based on a wedge-shaped cobalt-platinum component gradient film and a preparation method thereof.
Technical Field
Magnetic random access memory (Magnetic Random Accessory Memory, MRAM) is a promising memory technology in the future. MRAM has the advantages of high speed of SRAM, high density of DRAM, non-volatility of Flash, etc., and can replace the application of various memories in principle. At present, how to realize high reliability, high speed and low power consumption information writing technology is a key problem in MRAM design development. Recent developments in spin-orbit torque (spin orbit torque, SOT) have provided a new information writing technique for MRAM. Compared with the traditional writing technology using spin transfer torque (Spin transfer torque, STT-) the SOT driving magnetic moment turns over faster than the STT effect, lower power consumption and higher durability.
Current research on SOT-MRAM focuses mainly on the following three aspects, namely, the problem of device thermal stability caused by the limitation of the thickness of the magnetic layer (typically, 2 nm). And secondly, realizing unassisted magnetic field inversion on the vertical anisotropic film. Third is how to reduce the device dynamic write power consumption. In recent years, spin orbit torque effects in single-layer magnetic thin film systems provide new ideas for solving the effects. Compared with the traditional ferromagnetic/heavy metal double-layer film structure, the ferromagnetic/heavy metal double-layer film structure has the following advantages: (1) The SOT effect in the magnetic monolayer film structure is a bulk effect (rather than being limited to the interface to the ferromagnetic/heavy metal bilayer film structure), so that the thickness of the ferromagnetic layer can be increased, thereby improving the thermal stability of the device. (2) The magnetic single-layer film structure avoids the current shunt effect in the double-layer film structure, so that the magnetic single-layer film structure has higher current spin transfer efficiency, and the critical overturning current can be further reduced. Previous studies have demonstrated that a CoPt thin film structure with a composition gradient, in the presence of SOT effects, can achieve a reversal of magnetic moment in the presence of an external magnetic field. To achieve field-free switching, an additional film structure must be added (a built-in magnetic field is generated by using the coupling action between magnetic layers, such as adding a CoFe/Ru film), however, the addition of the film not only increases the complexity of the device, but also increases the power consumption of the device due to the current-splitting effect. How to further realize the field-free switching of SOT driving magnetic moment in a CoPt film without adding an additional film layer is not realized at present. The invention breaks CoPt through a wedge-shaped structure to break symmetry so as to realize SOT driving magnetic moment overturning without the assistance of an external magnetic field. The invention proves that the current regulation magnetic random access memory based on the wedge-shaped cobalt-platinum component gradient film has the advantages of larger resistance state change, lower power consumption and lower noise, and is a magnetic random access memory which is easy to realize by a large-scale preparation process.
Disclosure of Invention
The invention belongs to the field of magnetic random access memories, and particularly relates to a magnetic random access memory based on a wedge-shaped cobalt-platinum component gradient film and a preparation method thereof.
A current regulation magnetic random access memory based on a wedge-shaped cobalt-platinum component gradient film has a structure as follows: the protective layer, the film layer and the buffer layer are sequentially arranged from top to bottom. The protective layer, the film layer and the buffer layer are manufactured into a cross Hall Bar structure through micro-nano processing, and 4 electrodes are manufactured for electrical test. The thin film layer is composed of a Pt, co, pt, co, pt, co, mgO structure from bottom to top, and three layers of Co/Pt double-layer films with different thicknesses jointly construct the magnetic perpendicular anisotropy of the device. Wherein the lowermost Pt layer and the uppermost Co layer adopt reverse wedge-shaped structures during preparation, and the defects of magnetic symmetry on the structures are caused. The MgO layer further enhances the perpendicular anisotropy of the thin film layer. The resistance value of the thin film layer Is detected by the other two parallel electrodes of the storage device along the electrode vertical to the thickness change direction of the sensing device, and the resistance of the device Is changed along with the increase of the regulating current, so that the information storage Is realized.
Preferably, the electrode is made of conductive material, such as Al, pt or Au, and has a thickness of 40nm.
Preferably, the protective layer is a protective material, and the Ru thickness is 3nm.
Preferably, the buffer layer is made of buffer material, and Ru thickness is 3nm.
The Ru layer is used as a buffer layer to increase the metal film and SiO 2 Adhesion and planarity of the substrate. The components of the film layer mainly comprise magnetic materials Co and heavy metal materials Pt, wherein Co is used as magnetic metal to form the vertical anisotropy of the film, the addition of the Pt layer enhances the magnetic vertical anisotropy of the film, and the addition of the Pt layer is different from the existing magnetic random access memory in the aspect of magnetic anisotropy, and the existence of the wedge-shaped structure does not need a thicker heavy metal layer to provide self-rotational flow for magnetic domain inversion of the film. The film layer is mainly composed in two gradient change modes: 1. the structure of the catalyst is that the thickness of Co is continuously increased from bottom to top and the thickness of Pt is continuously reduced from bottom to top, wherein the structure is Pt (0.6-1.0) \Co (0.2-0.4) \Pt (0.4-0.8) \Co (0.4-0.6) \Pt (0.2-0.6) \Co (0.8-1.2) \MgO (1.0-2.0) (the thickness is in nanometer units). 2. Is formed by continuously thickness of Co from bottom to topThe thickness of Pt is continuously increased while the structure is from bottom to top that of Pt (0.2-0.6) \Co (0.8-1.2) \Pt (0.4-0.8) \Co (0.4-0.6) \Pt (0.6-1.0) \Co (0.2-0.4) \MgO (1-2) (the thickness is in nanometer). The design of the two structures ensures the gradient change of the components and the overall magnetic perpendicular anisotropy of the film. The lowermost Pt layer and the uppermost Co layer of the thin film layer each have an opposite wedge-shaped structure in order to secure its own asymmetry as described above.
The preparation method of the magnetic random access memory based on the wedge-shaped cobalt-platinum component gradient film comprises the following steps: sputtering a Ru layer, a Pt layer, a Co layer, a Pt layer, a MgO layer and a Ru layer on a silicon substrate by a magnetron sputtering system in sequence; wherein in order to ensure that the lowermost Pt layer and the uppermost Co layer are wedge-shaped, the rotation of a turntable of magnetron sputtering is stopped when the two layers are sputtered, and then the preparation of an opposite wedge-shaped structure is realized by adjusting the standing position of the two layers during growth; patterning the laminated layer into a cross structure by a method combining standard photoetching and ion etching after the film preparation is completed, and continuously plating electrodes on reserved positions on four pins of the cross structure.
Compared with the background technology, the invention has the following beneficial effects:
1. compared with the traditional magnetic memory, the invention provides the non-magnetic field overturning realized by the wedge-shaped structure, the resistance state change is larger, the process difficulty is reduced, the application limit is smaller, and the application range is enlarged. 2. Compared with the existing magnetic memory, the invention provides non-magnetic field overturning realized by the wedge-shaped structure, and the self-rotational flow is not required to be provided by a thicker heavy metal layer, so that the current shunting effect is weakened, and the power consumption of the device is greatly reduced.
Drawings
FIG. 1 is a schematic diagram of a magnetic memory;
FIG. 2 is a schematic cross-sectional view of a thin film structure;
FIG. 3 is a cross-sectional view of a device;
FIG. 4 is a graph of device resistance change after a modulating pulse current is applied;
Detailed Description
The invention aims to provide a current-regulation magnetic random access memory based on a wedge-shaped cobalt-platinum component gradient film. The invention comprises the following steps: the symmetry defect of the device is caused by the design of the wedge-shaped structure of the film, so that the current regulation and control under the condition of no magnetic field is realized.
The invention aims at realizing the following technical scheme:
current regulation magnetic random access memory based on wedge-shaped cobalt-platinum component gradient film
1) Pulse current Is introduced to the two electrodes in the X direction of the device, and the numerical value of the film resistor can be acquired at the two electrodes in the Y direction.
2) After pulse currents with different intensities are applied along the direction X perpendicular to the change direction of the wedge-shaped layer, the current can provide certain spin flow for the magnetic domain inversion of the film layer, and the resistance change can occur without providing stronger spin flow by a thicker heavy metal layer as in the conventional magnetic random access memory because of the defect of symmetry of the current, and the resistance of the current gradually changes along with the continuous inversion of the magnetic domain of the film layer. The domain will gradually return to the original state after the pulse current in the opposite direction is applied.
The invention is further described below with reference to the accompanying drawings and examples of implementation:
as shown in fig. 1, the protective layer, the film layer and the buffer layer are sequentially arranged from top to bottom. The protective layer, the film layer and the buffer layer are manufactured into a cross Hall Bar structure through micro-nano processing, and 4 electrodes are manufactured for electrical test. The thin film layer is composed of a Pt, co, pt, co, pt, co, mgO structure from bottom to top, and three layers of Co/Pt double-layer films with different thicknesses jointly construct the magnetic perpendicular anisotropy of the device. Wherein the lowermost Pt layer and the uppermost Co layer adopt reverse wedge-shaped structures during preparation, and the defects of magnetic symmetry on the structures are caused. The MgO layer further enhances the perpendicular anisotropy of the thin film layer. When the direction of the initial pulse current is X positive direction, the size is changed continuously, and the change condition of the resistance can be collected in Y direction.
As shown in FIG. 2, (1) the Ru layer is used as a buffer layer to prevent the continuity of the film morphology from being disrupted when heated during epitaxial growth. (2) The film layer is mainly composed of Co/Pt with different thickness gradients, and the perpendicular anisotropy of the film is formed by the mutual influence of the multiple layers of materials. (3) The lowermost Pt and uppermost Co of the thin film layers are wedge-shaped structures as indicated by the dotted lines. (4) The uppermost Ru has good oxidation resistance and acts as a protective layer.
As shown in fig. 3, four regions 1, 2, 3, and 4 are electrode regions, and 5 is a thin film sample region.
As shown in fig. 4, when the intensity of the pulse current is continuously increased in the X direction of the device, the resistance value thereof is slowly changed by the current.
Claims (6)
1. The magnetic random access memory based on the wedge-shaped cobalt-platinum component gradient film is characterized by comprising the following structure: the protective layer, the film layer and the buffer layer are sequentially arranged from top to bottom; establishing a space rectangular coordinate system, wherein the direction from the buffer layer to the protective layer is the positive direction of the z-axis; etching the protective layer, the film layer and the buffer layer to form a cross structure distributed along an x axis and a y axis, and plating 4 electrodes on the periphery of the cross structure;
the thin film layer is composed of a Pt, co, pt, co, pt, co, mgO structure from bottom to top, and three layers of Co/Pt double-layer films with different thicknesses jointly construct the magnetic perpendicular anisotropy of the device; the composition of the film layer is divided into two gradient change modes: 1. the thickness of Co is continuously increased from bottom to top, the thickness of Pt is continuously reduced, and the thickness of the film layer is 0.6-1.0nm, 0.2-0.4nm, 0.4-0.8nm, 0.4-0.6nm, 0.2-0.6nm, 0.8-1.2nm and 1.0-2.0nm from bottom to top;
2. the thickness of Co is continuously reduced from bottom to top, the thickness of Pt is continuously increased, and the thickness of a film layer is 0.2-0.6nm, 0.8-1.2nm, 0.4-0.8nm, 0.4-0.6nm, 0.6-1.0nm, 0.2-0.4nm and 1-2nm from bottom to top; the thickness of the lowermost Pt layer is gradually increased along the positive direction of the y axis, the thickness of the uppermost Co layer is gradually decreased along the positive direction of the y axis, and a wedge-shaped structure with opposite directions is prepared, so that the defect of magnetic symmetry on the structure is caused; the MgO layer further enhances the perpendicular anisotropy of the thin film layer.
2. The magnetic random access memory based on the wedge-shaped cobalt-platinum composition gradient film according to claim 1, wherein the electrode is made of a conductive material, and is made of Al, pt or Au, and the thickness of the electrode is 40nm.
3. The magnetic random access memory based on the wedge-shaped cobalt-platinum component gradient film according to claim 1, wherein the protective layer is made of a protective material, ru and has a thickness of 3-5nm.
4. The magnetic random access memory based on the wedge-shaped cobalt-platinum component gradient film according to claim 1, wherein the buffer layer is made of a buffer material Ru, and the thickness is 3-5nm.
5. The magnetic random access memory based on the wedge-shaped cobalt-platinum component gradient film according to claim 1, wherein pulse current Is introduced into two electrodes distributed along the x-axis direction of the space rectangular coordinate system, resistance change can be acquired at the two electrodes along the y-axis direction, and the resistance of the device correspondingly changes along with the continuous change of the intensity of the pulse current Is, so that information storage Is realized.
6. The method for preparing the magnetic random access memory based on the wedge-shaped cobalt-platinum component gradient film, which is disclosed in claim 1, is characterized in that:
sputtering a Ru layer, a Pt layer, a Co layer, a Pt layer, a MgO layer and a Ru layer on a silicon substrate by a magnetron sputtering system in sequence; wherein in order to ensure that the lowermost Pt layer and the uppermost Co layer are wedge-shaped, the rotation of a turntable of magnetron sputtering is stopped when the two layers are sputtered, and then the preparation of an opposite wedge-shaped structure is realized by adjusting the standing position of the two layers during growth; patterning the lamination into a cross structure by a method combining standard photoetching and ion etching after the film preparation is completed, and continuously plating electrodes on reserved positions on four pins of the cross structure.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101496120A (en) * | 2006-08-03 | 2009-07-29 | 原子能委员会 | Thin-layered magnetic device with high spin polarization perpendicular to the plane of the layers, and magnetic tunnel junction and spin valve using such a device |
| CN113437210A (en) * | 2021-06-24 | 2021-09-24 | 杭州电子科技大学 | Current regulation and control magnetic random access memory based on spin orbit torque |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101496120A (en) * | 2006-08-03 | 2009-07-29 | 原子能委员会 | Thin-layered magnetic device with high spin polarization perpendicular to the plane of the layers, and magnetic tunnel junction and spin valve using such a device |
| CN113437210A (en) * | 2021-06-24 | 2021-09-24 | 杭州电子科技大学 | Current regulation and control magnetic random access memory based on spin orbit torque |
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