Dual fixed layer magnetic tunnel junction, magnetic memory chip, and method of manufacturing the same

Abstract

The application relates to the field of magnetic storage chips in integrated circuits, in particular to a double-fixed-layer magnetic tunnel junction, a magnetic storage chip and a manufacturing method thereof. The application provides a double-fixed-layer magnetic tunnel junction, a magnetic storage chip and a manufacturing method thereof, which comprises a structure of a bottom fixed layer formed by three-layer ferromagnetic film structures through anti-parallel coupling, and further provides the thickness and material of each layer of the ferromagnetic film structure of the above structure from the perspective of the coupling magnetic field of the free layer to the bottom fixed layer, and further provides the structure of a top fixed layer on the basis of the bottom fixed layer. The application provides a manufacturing method of the double-fixed-layer magnetic tunnel junction and the magnetic storage chip. The application greatly reduces the information writing energy consumption of the MRAM chip based on STT-MTJ, greatly increases the durability of the MRAM chip based on STT-MTJ, and realizes the large-scale application of MRAM instead of DRAM and SRAM.

Description

Technical Field

[0001] This invention relates to the field of magnetic storage chips in integrated circuits, specifically to a double fixed-layer magnetic tunnel junction, a magnetic storage chip, and a method for manufacturing the same. Background Technology

[0002] A magnetic tunnel junction (MTJ) consists of two ferromagnetic thin-film structures sandwiching a tunneling layer of insulating oxide (usually MgO). By fixing the spin direction (also called magnetization direction) of one ferromagnetic thin-film structure (fixed layer) of the MTJ and changing the spin direction of the other ferromagnetic thin-film structure (free layer), two different resistance states can be generated. This can be used for storing and reading digital information "0" and "1", thus enabling its application in magnetic random access memory (MRAM).

[0003] MRAMs based on spin transfer moment (STT) MTJs have high information writing energy, resulting in poor durability because the high writing energy can easily damage the insulator of the tunneling layer. Since STT information writing is achieved by the magnetic torque generated by the spin polarization of the current in the fixed layer, which changes the spin direction of the free layer, a greater difference in the number of upward and downward spins generated by the spin polarization of the current in the fixed layer will decrease the writing current from one state to another (e.g., from parallel to antiparallel), while increasing the writing current for the opposite process (corresponding to antiparallel to parallel), and vice versa. Therefore, a dual-fixed-layer STT-MTJ structure and its MRAM structure and manufacturing method (Chinese Patent: CN2024106136795) have been proposed. Furthermore, considering the ease of manufacturing the top fixed layer, coercivity, and the coupling magnetic field between the fixed layer and the free layer, a dual-fixed-layer STT-MTJ and its MRAM structure and manufacturing method have been further proposed (Chinese Patent: CN2024110822877).

[0004] The aforementioned proposals did not simultaneously discuss the influence of the top and bottom fixed layers of the dual-fixed-layer structure on the free layer, and in particular, did not specify the structure of the bottom fixed layer. This invention proposes the structure and fabrication method of the top and bottom fixed layers of a dual-fixed-layer magnetic tunnel junction and the MRAM composed thereof, considering the coupling angle between the top fixed layer thin film structure (hereinafter referred to as the top fixed layer, Top, or Top Pin) and the bottom fixed layer thin film structure (hereinafter referred to as the bottom fixed layer, Bottom, or Btm, or Btm Pin), and the magnetization direction of the fabricated dual-fixed-layer magnetic tunnel junction. Designing the bottom fixed layer of an MRAM using conventional methods can lead to several problems, as explained below:

[0005] Figure 7 (A) shows the structures of the MTJ fixed layer of a single ferromagnetic thin-film structure (left) and the MTJ fixed layer composed of two ferromagnetic thin-film structures with antiferromagnetic coupling (right). The coupling layers between the ferromagnetic thin-film structures and between the ferromagnetic thin-film structures and the free layer are omitted. For the case of the single ferromagnetic thin-film structure fixed layer, the fixed layer generates two forces on the free layer, namely, static magnetic force and exchange coupling. Therefore, the force exerted by the fixed layer on the free layer is relatively large, which is not conducive to the information writing (i.e., spin inversion) of the free layer. In the two ferromagnetic thin-film structures with antiferromagnetic coupling on the right, generally, the magnetic moment (also known as magnetic momentum or magnetization) of the ferromagnetic body Pin 1, which is closer to the free layer, is smaller than that of Pin 2, which is farther from the free layer. Pin 1 generates a static magnetic force and an exchange coupling on the adjacent free layer. When the magnetic moment of Pin 1 is small, both of the above two effects are relatively small, especially the exchange coupling can be basically negligible. Although the magnetic moment of Pin 2, which is far away, is larger, due to the relatively large distance from the free layer, the static magnetic force and the exchange coupling generated on the adjacent free layer are also relatively small. Figure 7 (B) is Figure 7 (A) is a schematic diagram of the hysteresis loop when the two types of MTJ fixed layers in (A) generate magnetic coupling on the free layer. Although the effect of the exchange coupling on the free layer can be ignored, the static magnetic forces of Pin 1 and Pin 2 generate a coupling magnetic field (H bias ) on the free layer. For Figure 7 the structure in (A), assume that the free layer is a CoFeB alloy thin film with a thickness of x nanometers, and x is usually less than 3 nanometers. The ferromagnetic thin-film structure in the fixed layer is usually a multi-layer repeated structure of a Co and Pt composite structure, denoted as (Co / Pt)z; Figure 7 In the MTJ fixed layer of the single ferromagnetic thin-film structure in (A), z is L, while in the MTJ fixed layer of the two ferromagnetic thin-film structures with antiferromagnetic coupling, z of Pin 1 and Pin 2 are M and N respectively. Since both Pin 1 and Pin 2 are the same main structure (Co / Pt)z, the number of repetitions of the main structure is positively correlated with the magnetic moments of Pin 1 and Pin 2. As mentioned above, the magnetic moment of Pin 1 needs to be smaller than that of Pin 2, so M < N. Under the condition of the same main structure, by adjusting the thickness of the ferromagnetic thin-film structure or the number of repetitions z of the main structure (Co / Pt)z, the main parameters of the magnetic properties (including saturation magnetic moment, coercive force, and coupling of the fixed layer to the free layer, etc.) can be adjusted, and thus the limitations related to the thickness (here the number of layers) in the claim items are generated. Using a (Co / Pt) structure composed of Co with a thickness less than 0.8 nanometers and Pt with a thickness less than 0.5 nanometers that is commonly used, Figure 7(C) The coupling magnetic fields of the fixed layer to the free layer were compared when z is an integer L less than 9 in the MTJ fixed layer of a single ferromagnetic thin film structure (Pin 1), and z is M (<4) and N (<6) respectively in the MTJ fixed layers of two antiparallel coupled ferromagnetic thin film structures, Pin 1 and Pin 2, and L = M + N. Figure 7 As shown in (C), for MTJ diameters between 10 nm and 80 nm, the coupling magnetic field generated by the MTJ fixed layer of two antiparallel coupled ferromagnetic thin film structures on the free layer is much smaller than that of a fixed layer composed of a single ferromagnetic thin film structure. The smaller the coupling magnetic field (also known as coupling bias), the less energy is required for free layer reversal.

[0006] Based on the above, the influence of the top fixing layer should be further considered. Figure 8 (A) is a schematic diagram of a double-fixed-layer MTJ structure, where both the top and bottom fixed layers consist of two antiparallel coupled ferromagnetic thin-film structures, and the ferromagnetic thin-film structure closer to the free layer in the two fixed layers has a smaller magnetic moment. The purpose of using a smaller magnetic moment structure in the ferromagnetic thin-film structure closer to the free layer in the fixed layers is to reduce the coupling magnetic field between the fixed layer and the free layer. However, for... Figure 8 When the structure in (A) is excited by a magnetic field of 10 kOe and then removed from the external magnetic field, as follows: Figure 8 As shown in (B), the spin direction of the ferromagnetic thin film structure near the free layer in the top fixed layer is parallel to that of the ferromagnetic thin film structure near the free layer in the bottom fixed layer. Therefore, information cannot be written in the double fixed layer STT-MTJ as proposed in the previous proposal (Chinese Patent: CN2024106136795), and thus it cannot be applied.

[0007] Figure 9 The MTJ in this design consists of two antiparallel coupled ferromagnetic thin-film structures in both the top and bottom fixed layers. The ferromagnetic thin-film structure near the free layer in the bottom fixed layer has a larger magnetic moment, while the ferromagnetic thin-film structure near the free layer in the top fixed layer has a smaller magnetic moment. In this case, the spin directions of the ferromagnetic thin-film structures near the free layer in the top and bottom fixed layers are antiparallel. Therefore, the coupling magnetic fields of the top and bottom fixed layers to the free layer will cancel each other out, resulting in a smaller coupling magnetic field, which is theoretically usable.

[0008] Figure 10 (A) is Figure 9 The bottom and middle fixed layers are both composed of two antiparallel coupled ferromagnetic thin film structures, with the bottom fixed layer having a larger magnetic moment than the ferromagnetic thin film structure closest to the free layer. A schematic diagram of the bottom fixed layer and free layer of the double-fixed MTJ is shown. When the free layer is 2.3 nm and the distances between the free layer and Pin 1, and between Pin 1 and Pin 2 are both 0.9 nm, as... Figure 10(As shown in (B), Pins 1 and Pins 2 with different thicknesses are set, and the coupling magnetic field of the fixed layer to the free layer under MTJs with different diameters is Figure 10 (shown in (C). Below a diameter of 20 nm where STT-MTJs may be widely applied, the coupling magnetic fields under the three conditions are all greater than 1000 Oe; when the diameter is 40 nm, the coupling magnetic fields under the three conditions are all greater than 750 Oe. Considering that the coupling magnetic fields generated by the top and bottom fixed layers can cancel each other out during the application of the double fixed layer MTJ, it is considered that the coupling magnetic field generated by any one of the fixed layers of the double fixed layer is less than 750 Oe for large-scale application to be possible. When the above MTJ is below 40 nm, the coupling magnetic field generated by the bottom fixed layer is greater than 750 Oe, so it is difficult for this structure to be widely applied.

[0009] To solve the above problems, the present invention first proposes a double fixed layer magnetic tunnel junction, a magnetic storage chip, and a manufacturing method thereof, including a structure of a bottom fixed layer formed by anti-parallel coupling of three ferromagnetic thin film structures, and then proposes the thickness and materials of each ferromagnetic thin film structure of the above structure from the perspective of the coupling magnetic field of the bottom fixed layer to the free layer, and further proposes the structure of the top fixed layer based on the bottom fixed layer. At the same time, the double fixed layer MTJs of the proposed structure and their manufacturing methods are also proposed. Summary of the Invention

[0010] Based on the above background and problems, the present invention proposes a double fixed layer magnetic tunnel junction, a magnetic storage chip, and a manufacturing method thereof. Specifically:

[0011] A double fixed layer magnetic tunnel junction, the magnetic tunnel junction from near to far from the substrate is composed of a bottom fixed layer thin film structure, a bottom tunneling layer oxide thin film structure, a free layer thin film structure, a top tunneling layer oxide thin film structure, and a top fixed layer thin film structure; the bottom fixed layer thin film structure from near to far from the free layer is composed of a bottom first ferromagnetic thin film structure with a spin direction opposite to that of the ferromagnetic thin film structure closest to the free layer in the top fixed layer thin film structure, a bottom first anti-parallel coupling thin film structure, a bottom second ferromagnetic thin film structure with a spin direction opposite to that of the bottom first ferromagnetic thin film structure, a bottom second anti-parallel coupling thin film structure, and a bottom third ferromagnetic thin film structure with a spin direction opposite to that of the bottom second ferromagnetic thin film structure; the thickness D1 of the bottom first ferromagnetic thin film structure, the thickness D2 of the bottom second ferromagnetic thin film structure, and the thickness D3 of the bottom third ferromagnetic thin film structure satisfy the relationship of D1 < D2 and D1 < D3 and 0.29 < D2 / (D1 + D2 + D3) < 0.5. <(As shown in (B), Pins )

[0012] The following supplementary explanation is provided: The top fixed-layer thin-film structure in this proposal is also composed of multiple ferromagnetic thin-film structures. However, the spin directions of the ferromagnetic thin-film structure closest to the free layer in the top fixed-layer thin-film structure must be opposite to those of the ferromagnetic thin-film structure closest to the free layer in the bottom fixed-layer thin-film structure. This is the basis for enabling the dual fixed-layer MTJ of this invention to perform STT information writing. All thin-film structures in this specification refer to structures composed of one or more thin films. Specifically, a fixed-layer thin-film structure refers to a one- or multi-layer thin-film structure with ferromagnetism as its primary property, serving as the fixed layer of the magnetic tunnel junction. A bottom tunneling layer oxide thin-film structure refers to a one- or multi-layer thin-film structure primarily composed of oxides, serving as the tunneling layer of the magnetic tunnel junction. A free-layer thin-film structure refers to a one- or multi-layer thin-film structure primarily composed of ferromagnetic thin films, serving as the free layer of the magnetic tunnel junction. In other words, a certain thin-film structure refers to a one- or multi-layer thin-film structure primarily composed of a certain (main characteristic or main material). The aforementioned fixed-layer thin-film structure can also be called a fixed layer; similarly, free-layer thin-film structures can also be simply referred to as free layers. Since the main components of the bottom first ferromagnetic thin film structure, the bottom second ferromagnetic thin film structure, and the bottom third ferromagnetic thin film structure are the same in this proposal, this proposal adjusts the main parameters of magnetic properties (including saturation magnetic moment, coercivity, and coupling of the fixed layer to the free layer) by adjusting the thickness of the ferromagnetic thin film structure, thereby generating the above-mentioned thickness-related limitations, as detailed in the embodiments.

[0013] According to the double-fixed-layer magnetic tunnel junction provided by the present invention, the bottom first ferromagnetic thin film structure is composed of an integer n repeating structures of two thin films, a cobalt metal thin film and a platinum thin film, arranged from near to far from the substrate, upon which a cobalt metal thin film and a cobalt-iron-boron alloy thin film are deposited sequentially, and the integer n is 0 or 1; the bottom second ferromagnetic thin film structure is composed of an integer m repeating structures of two thin films, a cobalt metal thin film and a platinum thin film, arranged from near to far from the substrate, upon which a cobalt metal thin film is deposited; the bottom third ferromagnetic thin film structure is composed of an integer l repeating structures of two thin films, a cobalt metal thin film and a platinum thin film, arranged from near to far from the substrate, upon which a cobalt metal thin film is deposited.

[0014] To further clarify the above: The integer x repeating structures of a cobalt (Co) thin film and a platinum (Pt) thin film are usually denoted as (Co / Pt)x, representing x (x = n, m, l) repeating structures with Co below and Pt above. Other structures can be deduced similarly. The cobalt-iron-boron alloy of the bottom first ferromagnetic thin film structure is essential for the formation of the subsequent magnesium oxide tunneling layer. Based on some experimental and simulation results, a smaller thickness of the bottom first ferromagnetic thin film structure reduces the coupling magnetic field generated by the bottom fixed layer on the free layer. The relationships between n, m, and l mentioned above are also derived from the aforementioned thickness relationships.

[0015] The double-fixed-layer magnetic tunnel junction provided by the present invention includes the following structure:

[0016] (1.1) The top fixing layer thin film structure is composed of a top first ferromagnetic thin film structure, a top first antiparallel coupling thin film structure, a top second ferromagnetic thin film structure with the opposite spin direction to the top first ferromagnetic thin film structure, a top first oxide coupling thin film structure, and a top third ferromagnetic thin film structure with the same spin direction as the top second ferromagnetic thin film structure, arranged from near to far from the substrate; the top of the top fixing layer thin film structure is composed of a magnesium oxide thin film for improving magnetic vertical anisotropy.

[0017] (1.2) The top fixing layer thin film structure is composed of a top first ferromagnetic thin film structure, a top first antiparallel coupling thin film structure, a top second ferromagnetic thin film structure with the opposite spin direction to the top first ferromagnetic thin film structure, a top first oxide coupling thin film structure, a top third ferromagnetic thin film structure with the same spin direction as the top second ferromagnetic thin film structure, a top second oxide coupling thin film structure, and a top fourth ferromagnetic thin film structure with the same spin direction as the top third ferromagnetic thin film structure, from near to far from the substrate. The top of the top fixing layer thin film structure is composed of a magnesium oxide thin film structure for improving magnetic vertical anisotropy.

[0018] (1.3) The top fixing layer thin film structure is composed of a top first ferromagnetic thin film structure, a top first oxide coupling thin film structure, a top second ferromagnetic thin film structure with the same spin direction as the top first ferromagnetic thin film structure, a top first antiparallel coupling thin film structure, a top third ferromagnetic thin film structure with the opposite spin direction to the top second ferromagnetic thin film structure, a top second oxide coupling thin film structure, and a top fourth ferromagnetic thin film structure with the same spin direction as the top third ferromagnetic thin film structure, arranged from near to far from the substrate. The top of the top fixing layer thin film structure is composed of an antiferromagnetic thin film structure for spin pinning.

[0019] (1.4) The top fixing layer thin film structure is composed of a top first ferromagnetic thin film structure, a top first oxide coupling thin film structure, a top second ferromagnetic thin film structure with the same spin direction as the top first ferromagnetic thin film structure, a top first antiparallel coupling thin film structure, a top third ferromagnetic thin film structure with the opposite spin direction to the top second ferromagnetic thin film structure, a top second oxide coupling thin film structure, a top fourth ferromagnetic thin film structure with the same spin direction as the top third ferromagnetic thin film structure, a top third oxide coupling thin film structure, and a top fifth ferromagnetic thin film structure with the same spin direction as the top fourth ferromagnetic thin film structure, from near to far from the substrate. The top of the top fixing layer thin film structure is composed of a magnesium oxide thin film structure for improving magnetic vertical anisotropy.

[0020] (1.5) The top fixing layer thin film structure is composed of a top first ferromagnetic thin film structure, a top first antiparallel coupling thin film structure, a top second ferromagnetic thin film structure with the opposite spin direction to the top first ferromagnetic thin film structure, a top first oxide coupling thin film structure, a top third ferromagnetic thin film structure with the same spin direction as the top second ferromagnetic thin film structure, a top second antiparallel coupling thin film structure, and a top fourth ferromagnetic thin film structure with the opposite spin direction to the top third ferromagnetic thin film structure, from near to far from the substrate. The top of the top fixing layer thin film structure is composed of an antiferromagnetic thin film structure for spin pinning.

[0021] The following is a supplementary explanation of the above five novel MTJ structures: The above five structures were proposed after the bottom fixed layer structure was determined. Considering how to arrange the spin directions of the ferromagnetic layers of the bottom and top fixed layers in a predetermined manner after the magnetic tunnel junction is formed, and considering factors such as minimizing the coupling magnetic field of the top fixed layer to the free layer, the proposals were made for the top fixed layer.

[0022] According to the double-fixed-layer magnetic tunnel junction provided by the present invention, the material of the antiparallel coupled thin film structure is usually either ruthenium or iridium; the oxide coupled thin film structure is composed of magnesium oxide containing either iron or cobalt plus boron and being thicker than the magnesium oxide tunneling layer, iron oxide, and any one of the following: iron oxide and cobalt oxide.

[0023] According to the double-fixed-layer magnetic tunnel junction provided by the present invention, the antiferromagnetic thin film structure contains at least one antiferromagnetic material selected from manganese-platinum alloy or manganese-iridium alloy.

[0024] To further clarify the above: In this proposal, the spin direction of the multilayer ferromagnetic thin film structure needs to be arranged in an antiparallel manner through antiparallel coupling, while oxide coupling is used to form a parallel spin direction arrangement.

[0025] On the other hand, the present invention also provides a method for manufacturing a dual-fixed-layer magnetic tunnel junction magnetic memory chip based on a dual-fixed-layer magnetic tunnel junction, comprising the following steps:

[0026] (2.1) Fabrication of the peripheral circuitry of the magnetic storage chip on the substrate;

[0027] (2.2) Fabrication of the bottom electrode of the magnetic tunnel junction on the metal interconnect layer of the peripheral circuit;

[0028] (2.3) Prepare the connection layer between the bottom electrode and the bottom fixing layer thin film structure;

[0029] (2.4) Prepare the bottom first ferromagnetic thin film structure, the bottom first antiparallel coupling thin film structure, the bottom second ferromagnetic thin film structure, the bottom second antiparallel coupling thin film structure, and the bottom third ferromagnetic thin film structure containing the bottom fixed layer thin film structure;

[0030] (2.5) Prepare the bottom tunneling layer oxide thin film structure;

[0031] (2.6) Prepare the free layer thin film structure;

[0032] (2.7) Prepare the top tunneling layer oxide thin film structure;

[0033] (2.8) Prepare the top fixing layer thin film structure;

[0034] (2.9) Prepare a top protective layer;

[0035] (2.10) A device for patterning thin films to form magnetic storage chips;

[0036] (2.11) Connect and package the devices to form a chip.

[0037] To further clarify the above, the actual fabrication of MRAM chips is very complex. The steps described above are only the main steps related to the structure of this proposal during the formation and fabrication of MRAM chips. Many details exist between and before / after these steps, which are omitted here due to space limitations, but do not affect the characteristic steps claimed in this invention.

[0038] According to the manufacturing method of the dual fixed-layer magnetic tunnel junction magnetic memory chip provided by the present invention, after any step of preparing the top fixed-layer thin film structure, preparing the top protective layer, patterning the thin film, and forming the magnetic memory chip device, a magnetic field of not less than 1 Tesla is applied to magnetize the chip and then the process is restored to an environment without external field.

[0039] The following supplementary explanation is provided: Annealing and magnetization is a crucial manufacturing step for MRAM chips. For the characteristic structure proposed in this invention, the aforementioned annealing and magnetization process enables the alignment of the spin directions of each ferromagnetic thin film structure.

[0040] Traditional single-fixed-layer STT-MTJs use ferromagnetic thin films with high spin polarization as the fixing layer. While this reduces the write current in one direction, it increases the write current in the other. Using dual-fixed-layer STT-MTJs promises to solve this problem. Specifically, this invention proposes a top-and-bottom dual-fixed-layer structure and its manufacturing method, focusing on the coupling magnetic field between the fixing layer and the free layer, and the spin alignment control of the components of the fixing layer. This is expected to reduce the write current in both directions of the STT-MTJ while obtaining a stable magnetic storage MRAM chip. Attached Figure Description

[0041] Figure 1 As one embodiment of the present invention, this is a schematic diagram of the basic structure of a double-fixed-layer magnetic tunnel junction (MTJ) device with a characteristic bottom fixed-layer structure.

[0042] Figures 2-6 These are five embodiments of the present invention, namely five based on Figure 1 A schematic diagram of the structure of a double-fixed-layer MTJ with a characteristic bottom fixed-layer structure and different top fixed layers.

[0043] Figure 7 (A) shows the structure of the MTJ fixed layer of a single ferromagnetic thin film structure and the MTJ fixed layer of two antiparallel coupled ferromagnetic thin film structures. The coupling layers between the ferromagnetic thin film structures and between them and the free layer are omitted. (B) is a schematic diagram of the hysteresis loop when the MTJ fixed layer generates magnetic coupling with the free layer. (C) is a comparison of the coupling fields generated by the two types of MTJ fixed layers in (A) on the free layer at different MTJ device diameters.

[0044] Figure 8 (A) is a schematic diagram of a double-fixed-layer MTJ structure in which both the top and bottom fixed layers are composed of two antiparallel coupled ferromagnetic thin film structures, and the magnetic moment of the ferromagnetic thin film structure closer to the free layer in the two fixed layers is smaller; (B) is a schematic diagram of the spin direction arrangement of each ferromagnetic thin film structure in (A) under a magnetic field of 10kOe and under the condition that the external magnetic field is removed.

[0045] Figure 9 This is a schematic diagram showing the arrangement of the spin directions of the double-fixed-layer MTJ structure and each ferromagnetic thin film structure after excitation with 10kOe and removal of the external magnetic field, where both the top and bottom fixed layers are composed of two antiparallel coupled ferromagnetic thin film structures, and the magnetic moment of the ferromagnetic thin film structure near the free layer in the bottom fixed layer is larger than that in the top fixed layer.

[0046] Figure 10 (A) is Figure 9 (A) is a schematic diagram of the bottom fixed layer and free layer of a double-fixed MTJ, where the bottom fixed layer is composed of two antiparallel coupled ferromagnetic thin film structures and the ferromagnetic thin film structure of the bottom fixed layer has a larger magnetic moment than the free layer. (B) shows three different thickness combinations of the two ferromagnetic thin film structures constituting the bottom fixed layer in (A). (C) shows the result of the coupling magnetic field of the bottom fixed layer to the free layer with the diameter of the MTJ device when there are three different thickness combinations in (B).

[0047] Figure 11 As one embodiment of the present invention, the top fixed layer of the structure is composed of two antiparallel coupled ferromagnetic thin film structures, the bottom fixed layer is composed of three antiparallel coupled ferromagnetic thin film structures, and the magnetic moments of the ferromagnetic thin film structures near the free layer in the bottom and top fixed layers are relatively small. After being excited by 10kOe and the external magnetic field is removed, the schematic diagram shows the arrangement of the spin directions of the double fixed layer MTJ structure and each ferromagnetic thin film structure.

[0048] Figure 12 As one embodiment of the present invention, (A) is Figure 11 (A) is a schematic diagram of the bottom fixed layer and free layer of a double-fixed MTJ, where the bottom fixed layer is composed of three antiparallel coupled ferromagnetic thin film structures and the magnetic moment of the ferromagnetic thin film structure closest to the free layer is smaller. (B) shows eight different thickness combinations of the three ferromagnetic thin film structures constituting the bottom fixed layer in (A). (C) shows the result of the coupling magnetic field of the bottom fixed layer to the free layer with the diameter of the MTJ device when there are eight different thickness combinations in (B).

[0049] Figure 13 for Figure 12 The change in the coupling magnetic field of the bottom fixed layer to the free layer when the thicknesses of the three ferromagnetic thin film structures constituting the fixed layer from near to far from the free layer are D1, D2, and D3, respectively, is calculated when the ratio of D2 / (D1+D2+D3) changes under the condition that the MTJ device has a diameter of 20 nanometers.

[0050] Figure 14 As one embodiment of the present invention, (A) is Figure 11 Schematic diagram of the structure of the free layer part of the double-fixed layer MTJ bottom fixed layer, where the bottom fixed layer is composed of three antiferromagnetically coupled ferromagnetic thin film structures, and the magnetic moment of the ferromagnetic thin film structure of the bottom fixed layer close to the free layer is relatively small; (B) shows six different thickness combinations of the three ferromagnetic thin film structures constituting the bottom fixed layer in (A); (C) and (D) show the results of the coupling magnetic field of the bottom fixed layer to the free layer varying with the diameter of the MTJ device for the six different thickness combinations in (B).

[0051] Figure 15 is Figures 2-6 Comparison of the magnetic coupling fields generated by the top fixed layer of the double-fixed layer MTJ with the structures of 5 embodiments in the present invention on the free layer at different device diameters. Specific embodiments

[0052] The present invention will be described below with reference to the accompanying drawings and by way of examples of embodiments.

[0053] Embodiment 1:

[0054] Figure 11 This is one of the embodiments of the present invention and is a characteristic structure of the double-fixed layer MTJ of the present invention. The top fixed layer of this structure is composed of two antiferromagnetically coupled ferromagnetic thin film structures (top first and second ferromagnetic thin film structures), and the bottom fixed layer is composed of three antiferromagnetically coupled ferromagnetic thin film structures (bottom first, second, and third ferromagnetic thin film structures with magnetic moments m1, m2, and m3 respectively), and m2 < m1 + m3. When an additional downward magnetic field of 10 kOe is applied, Figure 11 the spin directions of all ferromagnetic thin film structures (with magnetic moments m1, m2, m3, m4, and m5 respectively) in the present invention are arranged downward. After removing the external magnetic field, m5 is larger than m4, m5 remains downward, and m4 and m5 form an antiferromagnetic relationship. Since m1 and m2, m2 and m3 are antiferromagnetically related to each other. Due to the above relationship of m2 < m1 + m3, m1 and m3 remain spin-down, and m2 spins upward because it is antiferromagnetically related to them. In this way, the bottom first ferromagnetic thin film structure m1 and the top first ferromagnetic thin film structure m4 can form an antiferromagnetic relationship, and thus, as described above, information writing of the double-fixed layer STT-MTJ can be performed.

[0055] Figure 12 (A) is Figure 11 A specific embodiment of the bottom structure in the structure. The thickness of the free layer FL is d5, and the distances between the free layer FL, the bottom first ferromagnetic thin film structure (Pin 1), the bottom second ferromagnetic thin film structure (Pin 2), and the bottom third ferromagnetic thin film structure (Pin 3) are d6, d7, and d8 respectively, with the unit of nanometer. The composition of each part from bottom to top is as follows:

[0056] Pin1:[Co(d1) / Pt(d2)]xn / Co(d3) / CoFeB(d4)

[0057] Pin2: [Co(d1) / Pt(d2)]xm / Co(d3)

[0058] Pin3: [Co(d1) / Pt(d2)]xl / Co(d3)

[0059] The units d1, d2, d3, and d4 within parentheses are nanometers. n, m, and l are integers representing the number of repetitions of [Co(d1) / Pt(d2)]. The film thickness can be adjusted by changing the values ​​of these integers. When d1 < 0.8, d2 < 0.5, d3 < 0.85, d4 < 2, d5 < 3, d6 < 1.2, d7 < 1.2, d7 < 1.2 (all units from d1 to d8 are nanometers), and the magnetic moment Ms of FL is kept < 1.5 Tesla and the magnetic moment Ms of the bottom fixed layer is kept < 1.4 Tesla, according to... Figure 12 (B) lists eight different thickness combinations of structures to obtain the coupled magnetic field between the bottom fixed layer and the free layer. Figure 12 A comparison was made in (C). It can be observed that when n is 0 and m is greater than 2 (Case#s-3 to Case#s-8), the coupling magnetic field between the bottom fixed layer and the free layer is less than 750 Oe within the compared diameter range of 10 nm to 80 nm. Therefore, the application conditions for a double-fixed-layer MTJ are met. However, when n is 0 and m equals 2 (Case#s-2), the coupling magnetic field between the bottom fixed layer and the free layer is greater than 750 Oe within the compared diameter range of 10 nm to 80 nm. In particular, the coupling magnetic field for reference n equal to 7 is greater than 1500 Oe, and based on the aforementioned analysis, it cannot be applied.

[0060] Figure 13 It is aimed at Figure 12 (B) For various double-fixed-layer MTJ structures at 20 nm, the ratio of the thickness of Pin 2 (Pin 2) to the sum of the thicknesses of Pin 1 (Pin 1), Pin 2, and Pin 3 (Pin 3) is denoted as Pin 2 / (Pin 1 + Pin 2 + Pin 3). Using this ratio as the x-axis and the coupling magnetic field value of the bottom fixed layer to the free layer as the y-axis, it is found that Pin 2 / (Pin 1 + Pin 2 + Pin 3) has a linear relationship with the coupling magnetic field. It is found that to achieve a coupling magnetic field less than 750 Oe, Pin 2 / (Pin 1 + Pin 2 + Pin 3) needs to be greater than 0.35. When Pin 2 / (Pin 1 + Pin 2 + Pin 3) is 0.5, the coupling magnetic field is 0, which is the ideal situation. However, because of the previous (… Figure 11Example) The requirement for the spin direction arrangement is m2 < m1 + m3, that is, Pin2 / (Pin1 + Pin2 + Pin3) needs to be less than 0.5. Considering the 20 nanometers compared here, and the previous results ( Figure 7 (C), Figure 10 (C), Figure 12 (C)) show that the smaller the diameter, the larger the coupling magnetic field. Therefore, the proposal of the present invention considers that the coupling magnetic field needs to be less than 1000 Oe. So the following conditions need to be met: 0.29 < Pin2 / (Pin1 + Pin2 + Pin3) < 0.50. It should be noted that since Figure 13 mainly uses an alloy of Co and Pt, the thickness or the number of repetitions of the two-layer thin films of the main structure (Co / Pt) is positively correlated with magnetic properties such as the magnetic moment (m).

[0061] Figure 14 (A) is also based on Figure 12 the same characteristic structure, but adjusts the thicknesses of the bottom first ferromagnetic thin film structure (Pin 1), the bottom second ferromagnetic thin film structure (Pin 2), and the bottom third ferromagnetic thin film structure (Pin 3). The n value of [Co(d1) / Pt(d2)]n of the bottom first ferromagnetic thin film structure is adjusted to 1 and 2. For the specific thickness, refer to Figure 14 (B). When n is 1 and 2, the coupling magnetic field of the fixed layer to the free layer obtained under different diameter MTJ conditions of this structure is respectively as shown in Figure 14 (C) and Figure 14 (D). When n = 1, when the diameter is more than 30 nanometers, it can ensure that the coupling magnetic field of the fixed layer to the free layer is less than 750 Oe. However, when n = 2, when the diameter is more than 60 nanometers, it can ensure that the coupling magnetic field of the fixed layer to the free layer is less than 750 Oe. Because for MRAM based on STT-MTJ when replacing SRAM and DRAM applications, the device size (high integration density) is an important measurement index. Considering the actual application, usually MRAM is most expected to replace DRAM and SRAM on a large scale when it is below 40 nanometers. That is to say, when n = 1, this structure is expected to be applied on a large scale, while when n = 2, it is difficult to be applied on a large scale. Considering Figure 12 (C), in the structure proposed in the present invention, it is necessary to satisfy n < 2, preferably n = 0. In the embodiment of this proposal, n < 2 is equivalent to that the thickness of the bottom first ferromagnetic thin film structure (Pin 1 or m1) is less than 2.8 nanometers.

[0062] Example 2:

[0063] Figure 1As one embodiment of the present invention, this is a schematic diagram of the basic structure of a double-fixed-layer magnetic tunnel junction (MTJ) device with a characteristic bottom fixed-layer structure. 7 is a free layer, and 1 and 2 are the bottom tunneling layer oxide thin film structure and the top tunneling layer oxide thin film structure, respectively. 81, 82, and 83 are the first, second, and third bottom ferromagnetic thin film structures, respectively, and 31 and 32 are the first and second bottom antiparallel coupled thin film structures, respectively. 81 and 82 are antiparallel coupled through 31, and 82 and 83 are antiparallel coupled through 32. 81, 82, 83, 31, and 32 constitute the characteristic structure of the bottom fixed-layer thin film structure of the double-fixed-layer structure proposed in this invention. 9 is the top fixed-layer thin film structure.

[0064] After excitation, the structure enables the spin direction of the first ferromagnetic thin film structure of the top fixed layer thin film structure to be opposite to the spin direction of the bottom first ferromagnetic thin film structure, and the spin direction of the bottom first ferromagnetic thin film structure is opposite to the spin direction of the second ferromagnetic thin film structure, and the spin direction of the second ferromagnetic thin film structure is opposite to the spin direction of the third ferromagnetic thin film structure. Figure 1 The spin direction of the first ferromagnetic thin film structure at the bottom is downward, while the tops of the second and third ferromagnetic thin film structures at the bottom are upward, downward, and upward, respectively. Conversely, if the spin direction of the first ferromagnetic thin film structure at the bottom is upward, the directions of the other ferromagnetic thin film structures will also change. As mentioned earlier, the top fixing layer thin film structure in this invention is also composed of multiple ferromagnetic thin film structures. Figure 1 The top fixing layer is not specified in detail, so although the spin direction of the first ferromagnetic thin film structure of the top fixing layer thin film structure is opposite to the spin direction of the bottom first ferromagnetic thin film structure. Figure 1 Treating the top fixed layer thin film structure as a whole, it is impossible to specify its spin direction.

[0065] Example 3:

[0066] Figures 2-6 These are five embodiments of the present invention, namely five based on Figure 1 A schematic diagram of the structure of a double-fixed-layer MTJ with a characteristic bottom fixed-layer structure and different top fixed layers.

[0067] Figure 2 91 and 92 are top first and top second ferromagnetic thin film structures that are antiparallel coupled through the top first antiparallel coupling thin film structure 33. 101 is the top third ferromagnetic thin film structure, which is parallel coupled to the top second ferromagnetic thin film structure 92 through the top first oxide coupling thin film structure 41. 5 is a magnesium oxide thin film structure used to improve magnetic vertical anisotropy. The above 91, 33, 92, 41, and 101 constitute... Figure 2The top fixed layer thin film structure. After excitation and removal of the external magnetic field, when the spin direction of the bottom first ferromagnetic thin film structure is downward, the spin directions of the top first, second, and third ferromagnetic thin film structures are upward, downward, and downward, respectively. Conversely, when the spin direction of the bottom first ferromagnetic thin film structure is upward, the spin directions of the top first, second, and third ferromagnetic thin film structures are downward, upward, and upward, respectively.

[0068] Figure 3 exist Figure 2 Above the top third ferromagnetic thin film structure 101, a top fourth ferromagnetic thin film structure parallel to its spin direction is formed through the top second oxide coupling thin film structure 42, followed by the formation of a magnesium oxide thin film structure 5 to improve magnetic perpendicular anisotropy. The above 91, 33, 92, 41, 101, 42, and 102 constitute... Figure 3 The top fixed layer thin film structure. After excitation and removal of the external magnetic field, when the spin direction of the first ferromagnetic thin film structure at the bottom is downward, the spin directions of the first, second, third, and fourth ferromagnetic thin film structures at the top are upward, downward, downward, and downward, respectively; conversely, the corresponding relationship is also satisfied.

[0069] Figure 4 The top first ferromagnetic thin film structure 101 and the top second ferromagnetic thin film structure 91 are parallelly coupled through the top first oxide coupling thin film structure 41. 91 is then antiparallel coupled to the top third ferromagnetic thin film structure 92 through the top first antiparallel coupling thin film structure 33. 92 is then parallel coupled to the top fourth ferromagnetic thin film structure 102 through the top second oxide coupling thin film structure 42. An antiferromagnetic thin film structure 6 for spin pinning is then formed on top of 102. The structures 101, 41, 91, 33, 92, 42, and 102 constitute... Figure 4 The top fixed layer thin film structure. After excitation and removal of the external magnetic field, when the spin direction of the first ferromagnetic thin film structure at the bottom is downward, the spin directions of the first, second, third, and fourth ferromagnetic thin film structures at the top are upward, upward, downward, and downward, respectively; conversely, the corresponding relationship is also satisfied.

[0070] Figure 5 exist Figure 4 A third oxide coupling thin film structure 43 is formed on top of 102 and coupled parallel to the fifth ferromagnetic thin film structure 103. A magnesium oxide thin film structure 5, used to improve magnetic vertical anisotropy, is then formed on top of 103. The structures 101, 41, 91, 33, 92, 42, 102, 43, and 103 constitute... Figure 5The top fixed layer thin film structure. After excitation and removal of the external magnetic field, when the spin direction of the first ferromagnetic thin film structure at the bottom is downward, the spin directions of the first, second, third, fourth, and fifth ferromagnetic thin film structures at the top are upward, upward, downward, downward, and downward, respectively; conversely, the corresponding relationship is also satisfied.

[0071] Figure 6 91 and 92 are top first and top second ferromagnetic thin film structures that are antiparallel coupled through the top first antiparallel coupling thin film structure 33. 93 is the top third ferromagnetic thin film structure, which is parallel coupled to the top second ferromagnetic thin film structure 92 through the top first oxide coupling thin film structure 41. The top fourth ferromagnetic thin film structure 94 is antiparallel coupled to the top third ferromagnetic thin film structure 93 through the top second antiparallel coupling thin film structure 34. An antiferromagnetic thin film structure 6 for spin pinning is then formed on top of 94. The above-mentioned 91, 33, 92, 41, 93, 34, and 94 constitute... Figure 6 The top fixed layer thin film structure. After excitation and removal of the external magnetic field, when the spin direction of the bottom first ferromagnetic thin film structure is downward, the spin directions of the top first, second, third, and fourth ferromagnetic thin film structures are upward, downward, downward, and upward, respectively; conversely, the corresponding relationship is also satisfied.

[0072] Figure 15 for Figures 2-6 A comparison of the coupling magnetic fields generated by the top fixed layer of the double-fixed-layer MTJ in five embodiments of the Chinese model on the free layer at different device diameters. (d), (e), (f), (g), and (h) correspond to... Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 It can be seen that all five structures can satisfy the requirement that the coupling magnetic field of the top fixed layer to the free layer is less than 750 Oe when the diameter is greater than 20 nanometers. Since actual MTJs are composed of multiple nanoscale thin films, the preparation conditions of the thin films will affect the relevant properties to some extent. Therefore, this proposal only specifies the coupling magnetic fields of the top and bottom fixed layers to the free layer.

[0073] This proposal is expected to significantly reduce the energy consumption of information writing for STT-MTJ-based MRAM chips and greatly increase their durability, enabling the large-scale application of MRAM to replace DRAM and SRAM.

[0074] All the above embodiments merely illustrate certain implementations of the present invention and are described in detail, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A double-fixed-layer magnetic tunnel junction, characterized in that, The magnetic tunnel junction is composed of a bottom fixed layer thin film structure, a bottom tunneling layer oxide thin film structure, a free layer thin film structure, a top tunneling layer oxide thin film structure, and a top fixed layer thin film structure from near to far from the substrate; the bottom fixed layer thin film structure is composed of a bottom first ferromagnetic thin film structure, a bottom first antiferromagnetic coupling thin film structure, a bottom second ferromagnetic thin film structure, a bottom second antiferromagnetic coupling thin film structure, and a bottom third ferromagnetic thin film structure from near to far from the free layer, where the spin direction of the bottom first ferromagnetic thin film structure is opposite to that of the ferromagnetic thin film structure closest to the free layer in the top fixed layer thin film structure; the thicknesses D1 of the bottom first ferromagnetic thin film structure, D2 of the bottom second ferromagnetic thin film structure, and D3 of the bottom third ferromagnetic thin film structure satisfy the relationship D1 < D2, D1 < D3, and 0.29 < D2 / (D1 + D2 + D3) < 0.

5.

2. The double-fixed-layer magnetic tunnel junction according to claim 1, characterized in that, The bottom first ferromagnetic thin film structure is formed by sequentially depositing a cobalt metal thin film and a cobalt iron boron alloy thin film on top of an integer n repetition structure of two thin films, namely a cobalt metal thin film and a platinum thin film, from near to far from the substrate, and the integer n is 0 or 1; the bottom second ferromagnetic thin film structure is formed by depositing a cobalt metal thin film on top of an integer m repetition structure of two thin films, namely a cobalt metal thin film and a platinum thin film, from near to far from the substrate; the bottom third ferromagnetic thin film structure is formed by depositing a cobalt metal thin film on top of an integer l repetition structure of two thin films, namely a cobalt metal thin film and a platinum thin film, from near to far from the substrate.

3. The double-fixed-layer magnetic tunnel junction according to claim 2, characterized in that, The top fixed layer thin film structure is composed of a top first ferromagnetic thin film structure, a top first antiferromagnetic coupling thin film structure, a top second ferromagnetic thin film structure, a top first oxide coupling thin film structure, and a top third ferromagnetic thin film structure from near to far from the substrate, where the spin direction of the top second ferromagnetic thin film structure is opposite to that of the top first ferromagnetic thin film structure; the top of the top fixed layer thin film structure is composed of a magnesium oxide thin film for enhancing magnetic perpendicular anisotropy.

4. The double-fixed-layer magnetic tunnel junction according to claim 2, characterized in that, The top fixed layer thin film structure is composed of a top first ferromagnetic thin film structure, a top first antiferromagnetic coupling thin film structure, a top second ferromagnetic thin film structure, a top first oxide coupling thin film structure, a top third ferromagnetic thin film structure, a top second oxide coupling thin film structure, and a top fourth ferromagnetic thin film structure from near to far from the substrate, where the spin direction of the top fourth ferromagnetic thin film structure is the same as that of the top third ferromagnetic thin film structure; the top of the top fixed layer thin film structure is composed of a magnesium oxide thin film structure for enhancing magnetic perpendicular anisotropy.

5. The double-fixed-layer magnetic tunnel junction according to claim 2, characterized in that, The top fixing layer thin film structure is composed of, from near to far from the substrate, a top first ferromagnetic thin film structure, a top first oxide coupling thin film structure, a top second ferromagnetic thin film structure with the same spin direction as the top first ferromagnetic thin film structure, a top first antiparallel coupling thin film structure, a top third ferromagnetic thin film structure with the opposite spin direction to the top second ferromagnetic thin film structure, a top second oxide coupling thin film structure, and a top fourth ferromagnetic thin film structure with the same spin direction as the top third ferromagnetic thin film structure; the top of the top fixing layer thin film structure is composed of an antiferromagnetic thin film structure for spin pinning.

6. The double-fixed-layer magnetic tunnel junction according to claim 2, characterized in that, The top fixing layer thin film structure is composed of, from near to far from the substrate, a top first ferromagnetic thin film structure, a top first oxide coupling thin film structure, a top second ferromagnetic thin film structure with the same spin direction as the top first ferromagnetic thin film structure, a top first antiparallel coupling thin film structure, a top third ferromagnetic thin film structure with the opposite spin direction to the top second ferromagnetic thin film structure, a top second oxide coupling thin film structure, a top fourth ferromagnetic thin film structure with the same spin direction as the top third ferromagnetic thin film structure, a top third oxide coupling thin film structure, and a top fifth ferromagnetic thin film structure with the same spin direction as the top fourth ferromagnetic thin film structure; the top of the top fixing layer thin film structure is composed of a magnesium oxide thin film structure for improving magnetic vertical anisotropy.

7. The double-fixed-layer magnetic tunnel junction according to claim 2, characterized in that, The top fixing layer thin film structure comprises, from near to far from the substrate, a top first ferromagnetic thin film structure, a top first antiparallel coupled thin film structure, a top second ferromagnetic thin film structure with the opposite spin direction to the top first ferromagnetic thin film structure, a top first oxide coupled thin film structure, a top third ferromagnetic thin film structure with the same spin direction as the top second ferromagnetic thin film structure, a top second antiparallel coupled thin film structure, and a top fourth ferromagnetic thin film structure with the opposite spin direction to the top third ferromagnetic thin film structure; the top of the top fixing layer thin film structure contains an antiferromagnetic thin film structure for spin pinning.

8. The double-fixed-layer magnetic tunnel junction according to any one of claims 1 to 7, characterized in that, The antiparallel coupling thin film structure is made of either ruthenium or iridium; the oxide coupling thin film structure is composed of either magnesium oxide containing either iron or cobalt plus boron and having a thickness greater than that of the tunneling layer magnesium oxide, iron oxide, or an oxide containing both iron and cobalt.

9. The double-fixed-layer magnetic tunnel junction according to claim 5 or 7, characterized in that, The antiferromagnetic thin film structure contains at least one type of antiferromagnetic material, either a manganese-platinum alloy or a manganese-iridium alloy.

10. A method for manufacturing a double-fixed-layer magnetic tunnel junction magnetic memory chip based on the double-fixed-layer magnetic tunnel junction according to any one of claims 1 to 7, comprising the following steps: Fabrication of the peripheral circuitry for the magnetic storage chip on a substrate; The bottom electrode of the magnetic tunnel junction is fabricated on the metal interconnect layer of the peripheral circuit; Prepare a connection layer between the bottom electrode and the bottom fixing layer thin film structure; Prepare a bottom first ferromagnetic thin film structure, a bottom first antiparallel coupling thin film structure, a bottom second ferromagnetic thin film structure, a bottom second antiparallel coupling thin film structure, and a bottom third ferromagnetic thin film structure containing the bottom fixed layer thin film structure; Prepare the bottom tunneling layer oxide thin film structure; Prepare the free layer thin film structure; Prepare the top tunneling layer oxide thin film structure; Prepare the top fixing layer thin film structure; Prepare a top protective layer; A device that patterns thin films to form magnetic storage chips; The components are connected and packaged to form a chip.

11. The method for manufacturing a dual-fixed-layer magnetic tunnel junction magnetic memory chip according to claim 10, characterized in that, The step of applying a magnetic field of not less than 1 Tesla to magnetize the device after any of the steps of preparing the top fixed layer thin film structure, preparing the top cover protective layer, patterning the thin film to form a magnetic storage chip, and then returning to an environment without external field.

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