Resistive memory structure and method of making the same

Abstract

The application discloses a resistive switching memory structure and a manufacturing method thereof. The resistive switching memory structure comprises, from bottom to top, a bottom electrode, a resistive switching layer and a top electrode. The upper surface of the bottom electrode and the lower surface of the resistive switching layer are in Schottky contact, and the lower surface of the top electrode and the upper surface of the resistive switching layer are in Ohmic contact. The resistive switching layer is a single oxide film layer. The materials of the bottom electrode and the top electrode are the same metal nitride, and the atomic number ratio of metal elements to nitrogen elements in the top electrode is greater than that in the bottom electrode. The application can simplify the structure of the memory, reduce the process complexity and manufacturing cost.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to a resistive variable memory structure and its fabrication method. Background Technology

[0002] Among emerging memory technologies, resistive switching memories (RSMs) based on redox reactions have attracted widespread attention due to their process compatibility with CMOS, superior performance, and potential for miniaturization. The basic switching unit of an RSM consists of a three-layer structure: metal-insulator-metal. The intermediate insulator material is typically a transition metal binary oxide, whose conductivity can be adjusted by ion migration induced by an externally applied electric field. Ion types include metal cations, proton charges, and oxygen ions (oxygen vacancies); the former is referred to as electrochemical metallization memory, and the latter as valence-variable memory. Valence-variable memory is more widely used in actual production due to its material selection, which is more compatible with CMOS (Complementary Metal-Oxide-Semiconductor) processes, and its superior device cycle performance. Its bottom electrode material is a metal with a high work function (e.g., Pt, TiN), forming a Schottky contact with the oxide insulating layer. Its top electrode requires high electrochemical activity to complete the redox reaction or ion exchange and form an ohmic contact with the oxide insulating layer; it is typically a metal with high oxygen affinity (e.g., Ta, Ti, Hf). In general, the switching behavior of resistive switching memory devices of the valence variable memory type is achieved by modulating the migration and redistribution of oxygen vacancy defects by an external electric field, thereby modulating the electrostatic barrier on the Schottky interface.

[0003] To ensure stable device performance, existing resistive switching memory (RSM) devices typically employ a structure with four or more film layers, from bottom to top: a bottom electrode, a single or multilayer oxide resistive switching layer, a top electrode, and an encapsulation layer (oxygen isolation layer). The main purpose of the encapsulation layer is to prevent the highly electrochemically active top electrode from being oxidized externally, thus affecting device performance. However, the existing RSM structure with four or more film layers presents challenges such as structural complexity, high process complexity, and high manufacturing costs. Summary of the Invention

[0004] The purpose of this invention is to propose a resistive variable memory structure and its fabrication method, thereby simplifying the memory structure and reducing process complexity and manufacturing costs.

[0005] To achieve the above objectives, in a first aspect, the present invention proposes a resistive switching memory structure, comprising: a bottom electrode, a resistive switching layer, and a top electrode stacked sequentially from bottom to top;

[0006] The upper surface of the bottom electrode and the lower surface of the resistive switching layer are in a Schottky contact, and the lower surface of the top electrode and the upper surface of the resistive switching layer are in an ohmic contact.

[0007] The resistive switching layer is a single-layer oxide film.

[0008] Both the bottom electrode and the top electrode are made of the same metal nitride, and the ratio of the number of metal elements to nitrogen elements in the top electrode is greater than that in the bottom electrode.

[0009] Optionally, the bottom electrode is made of poisoned TiN, and the top electrode is made of metallic TiN;

[0010] The Ti / N atom ratio in the metallic TiN is greater than that in the poisoned TiN.

[0011] Optionally, the Ti / N atomic ratio in the TiN material of the top electrode ranges from 1.5 to 2.5.

[0012] Optionally, the Ti / N atomic ratio in the TiN material of the bottom electrode ranges from 0.9 to 1.

[0013] Optionally, the surface of the top electrode and the bottom electrode near the resistive switching layer is an oxygen diffusion region, and the thickness of the oxygen diffusion region of the top electrode is 2.7 to 3.3 times the thickness of the oxygen diffusion region of the bottom electrode.

[0014] Optionally, the thickness of the resistive switching layer is positively correlated with the device area of ​​the resistive switching memory.

[0015] Optionally, the thickness of the top electrode is more than twice the thickness of the resistive switching layer.

[0016] Optionally, the resistive switching layer is made of tantalum oxide or hafnium oxide.

[0017] Secondly, the present invention also proposes a method for fabricating a resistive switching memory structure, comprising:

[0018] A metal nitride film is deposited on the substrate to form the bottom electrode;

[0019] A single-layer oxide film is deposited on the bottom electrode to form a resistive switching layer;

[0020] A metal nitride film is deposited on the resistive switching layer to form a top electrode;

[0021] The bottom electrode and the top electrode are both made of the same metal nitride, and the ratio of the number of metal elements to nitrogen elements in the top electrode is greater than that in the bottom electrode.

[0022] Optionally, the bottom electrode, the resistive switching layer, and the top electrode are formed using reactive magnetron sputtering.

[0023] Optionally, the bottom electrode is made of poisoned TiN, and the top electrode is made of metallic TiN;

[0024] The nitrogen flow rate used in forming the top electrode is 10–20 sccm;

[0025] The nitrogen flow rate used in forming the bottom electrode is 100-120 sccm.

[0026] The beneficial effects of this invention are as follows:

[0027] The resistive switching memory structure of this invention includes a bottom electrode, a resistive switching layer, and a top electrode stacked sequentially from bottom to top. The resistive switching layer is a single-layer oxide film. Both the bottom and top electrodes are made of the same metal nitride. The ratio of metal to nitrogen atoms in the top electrode is greater than that in the bottom electrode. Because of this higher ratio, the oxygen affinity of the top electrode is stronger than that of the bottom electrode, resulting in a more chemically active top electrode. This invention achieves oxygen affinity asymmetry in the vertical direction of the device structure by using metal nitrides with a higher ratio of metal to nitrogen atoms and those with a lower ratio as the top and bottom electrode materials, respectively. This asymmetry allows oxygen vacancies to move directionally during device operation, forming stable conductive channels. Therefore, the resistive switching memory structure of this invention only requires a single-layer resistive switching layer to meet the resistive switching behavior of the memory, eliminating the need for the multi-layer oxide resistive switching layers found in existing resistive switching memory systems. The variable layer structure simplifies the resistive switching behavior by enabling the switching layer to function. Simultaneously, due to the stronger oxygen affinity and more reactive chemical properties of the metal nitride film of the top electrode, its surface can react with oxygen in the air to form metal nitride and metal oxide films. This film prevents further oxidation of the top electrode film in an external oxygen environment, giving the top electrode both ohmic electrode functionality and self-oxygen isolation capabilities. It effectively prevents oxygen diffusion, making the device less susceptible to oxidation by the external oxygen environment. Therefore, the top electrode not only has excellent ohmic contact characteristics but also effectively prevents the diffusion of oxygen from the external environment, thus protecting the structure and performance of the resistive switching layer. This allows the single top electrode film to simultaneously perform both ohmic electrode and oxygen isolation functions, eliminating the need for the oxygen isolation layer (i.e., encapsulation layer) in existing resistive switching memory devices. This invention's resistive switching memory device only requires three films: the bottom electrode, the resistive switching layer, and the top electrode to meet device functions. Compared to traditional resistive switching memory structures with four or more films, this reduces the number of films, lowering the complexity and cost of the manufacturing process.

[0028] The system of the present invention has other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0029] The above and other objects, features and advantages of the present invention will become more apparent from the accompanying drawings, in which like reference numerals generally denote like parts.

[0030] Figure 1 This is a schematic diagram of a four-layer RRAM device with the same upper and lower electrode materials and a multi-layer resistive switching layer, which is a prior art technology.

[0031] Figure 2 High-resolution transmission electron microscope (TEM) image of a device structure in the prior art.

[0032] Figure 3 This is a schematic diagram of a resistive switching memory structure of the existing bivalent variable memory type (the right side shows detailed information about each layer and electrode materials).

[0033] Figure 4 This is a schematic diagram illustrating the feasibility analysis of a self-oxygen-isolated ohmic electrode in one embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram of the film structure of a resistive switching memory structure according to an embodiment of the present invention.

[0035] Figure 6 This is a complete structural schematic diagram of a resistive variable memory structure according to an embodiment of the present invention.

[0036] Figure 7 This is a schematic diagram of the device structure of each step in a method for fabricating a resistive variable memory structure according to an embodiment of the present invention.

[0037] Figure 8 This is a high-resolution transmission electron microscope image of the cross-section of a three-layer resistive switching memory in one embodiment of the present invention.

[0038] Figure 9a This is a secondary ion mass spectrometry (SIMS) characterization diagram of metallic TiN (N2 = 15 sccm) in one embodiment of the present invention.

[0039] Figure 9b This is a secondary ion mass spectrometry characterization diagram of poisoned TiN (N2 = 110 sccm) in one embodiment of the present invention.

[0040] Figure 10 This is a diagram showing the results of forward and reverse forming tests on a resistive variable memory in one embodiment of the present invention.

[0041] Figure 11 This is a graph showing the IV curve test results of a resistive variable memory in one embodiment of the present invention. Detailed Implementation

[0042] Existing resistive random access memory (RRAM) devices typically consist of four or more film layers, from bottom to top: a bottom electrode, a single or multilayer oxide resistive switching layer, a top electrode, and an encapsulation layer. The encapsulation layer, also known as the oxygen isolation layer, does not actually affect the device's switching function; its main purpose is to prevent the highly electrochemically active top electrode from being oxidized externally, thus affecting device performance. Redox reactions are crucial for the switching behavior of this type of RRAM, so the selection and combination of materials for its functional layers have a significant impact on both the microscopic reaction processes and the macroscopic device performance.

[0043] In resistive switching memory (RSM) devices of the valence-variable memory type, the oxide resistive switching layer is typically a binary oxide, such as SiOx, TiOx, NiOx, TaOx, and HfOx. RSMs using GeOx and TaOx as oxide resistive switching layers have on / off ratios exceeding 10. 9 Resistive switching memory devices using SiOx, HfOx, and TaOx as oxide resistive switching layers achieve sub-nanosecond switching speeds, and speeds exceeding 10⁻⁶ Ω·cm in TaOx. 12 Extremely high cycle durability. The bottom electrode typically uses TaN (tantalum nitride) or TiN (titanium nitride) materials. These materials have excellent conductivity and good compatibility with the resistive switching layer, effectively reducing leakage current and improving switching characteristics. For example, TaN electrodes, due to their high melting point and good chemical stability, maintain stable performance even under high-temperature processes, which is significant for improving device reliability and integration. The top electrode (ohmic electrode) generally uses metals such as Ti (titanium), Pt (platinum), or Ru (ruthenium). These materials have high conductivity and good chemical stability, providing a stable current path and reducing the interface resistance between the electrode and the resistive switching layer. The oxygen isolation layer typically uses materials such as TiN (titanium nitride), SiN (silicon nitride), or AlOx (aluminum oxide). These materials effectively prevent oxygen diffusion, protecting the structure and performance of the resistive switching layer, thereby improving device stability and reliability. For example, the SiN oxygen isolation layer effectively blocks the migration of oxygen ions through its dense structure, reducing oxygen vacancy drift during device operation and helping to maintain the uniformity and stability of the resistive switching layer.

[0044] When the oxygen affinities of the top and bottom electrodes are not significantly different, for example, when both electrodes are made of TiN or Pt, the intermediate oxide resistive switching layer generally needs to be a multilayer or intercalated structure rather than a single thin film. This is because a single oxide resistive switching layer thin film may not provide sufficient switching characteristics or stability in such cases. For example, studies have shown that using a multilayer TaOx resistive switching layer can significantly improve the device's cycle stability and data retention capability. Furthermore, multilayer or intercalated structures can improve device performance, such as increasing switching speed, cycle endurance, and data retention capability.

[0045] For example, existing technology 1 proposes a method based on asymmetric Ta2O 5-x / TaO 2-x Two-layer non-volatile storage devices, such as Figure 1 As shown, this device is a four-layer resistive switching memory structure, with both upper and lower electrodes made of the same material, Pt, using asymmetric Ta₂O. 5-x / TaO 2-x The double-layer structure serves as the resistive switching layer, utilizing Ta2O 5-x Layers and TaO 2-x An oxygen vacancy gradient forms between the layers, enabling localized resistive switching behavior. This resistive switching behavior is mainly attributed to the migration of oxygen vacancies and the formation and breakage of conductive filaments (nanoscale conductive channels) in Ta2O. 5-x The layer has a high oxygen vacancy concentration, while TaO 2-x The layer has a low oxygen vacancy concentration. This oxygen vacancy gradient makes the resistive switching behavior more stable and controllable. The device achieves a switching speed of 10 nanoseconds and a cycle endurance of over 10... 12 This significantly improves the lifespan of the device.

[0046] However, this technology has some drawbacks. First, the manufacturing process is relatively complex, requiring precise control of the thickness and composition of the bilayer structure, which increases manufacturing difficulty and cost to some extent. Second, due to the asymmetric bilayer structure, the device's performance stability may be affected by the oxygen vacancy gradient, leading to performance fluctuations under different operating conditions. Furthermore, the scalability of this structure faces challenges, especially in high-density storage applications; maintaining performance consistency and reliability requires further research. Finally, although the device exhibits excellent cycle durability, the formation and breakage of conductive filaments during long-term use may lead to a gradual decline in device performance, affecting its lifespan. Figure 2 As shown, Ta2O near the top electrode 5-x The switching layer (point A in the diagram) is lighter in color, while the TaO layer near the bottom electrode is lighter in color. 2-x The switch layer (point B in the image) is darker in color. Compare the unused sample (top left) with the 10-cycled sample. 6Ta2O in the secondary sample (top right) 5-x High-magnification images of the layer, obtained using energy-filtered transmission electron microscopy, revealed the presence of metallic Ta clusters in the cyclic sample.

[0047] If the intermediate oxide resistive switching layer is a single thin film, an encapsulation layer, also known as an oxygen isolation layer, is usually added above the top electrode. This is because the top electrode is typically chemically more reactive and readily reacts with the resistive switching layer and the external oxygen environment, leading to a degradation in device performance. Existing technology two proposes a resistive switching memory structure, the overall structure of which is as follows: Figure 3 As shown, it uses HfO2 as the resistive switching layer and employs different materials as electrodes and encapsulation layers to optimize device performance. Specifically, Pt or TiN is used as the oxygen isolation layer, with a thickness of 30 nm; high work function materials such as Pt or TiN are used as the bottom electrode to form a Schottky interface, with a thickness of 30 nm; while high oxygen affinity metallic Ti is used as the top electrode (ohmic electrode) to form an ohmic contact and promote the formation and migration of oxygen vacancies, with a thickness of 10, 30, or 60 nm; the intermediate oxide resistive switching layer uses HfO2, with a thickness of 5, 10, or 20 nm. The encapsulation layer material, such as TiN or Pt, has a significant impact on the formation and distribution of oxygen vacancies. The TiN encapsulation layer can effectively prevent oxygen diffusion, protect the structure and performance of the resistive switching layer, and participate in the formation process of oxygen vacancies, enhancing the resistive switching characteristics of the device. In contrast, the Pt encapsulation layer has less impact on oxygen diffusion and oxygen vacancy formation, resulting in relatively weaker resistive switching characteristics of the device.

[0048] This technical solution has several drawbacks. First, the device structure is relatively complex, involving multiple layers of materials, such as the bottom electrode, resistive switching layer, top electrode, and encapsulation layer, which increases the complexity and cost of the manufacturing process. Second, there are certain limitations in material selection. For example, while materials such as TiN and Pt exhibit good performance in experiments, their stability and reliability may vary under different operating conditions. Furthermore, the encapsulation layer material has a significant impact on device performance. Although the TiN encapsulation layer can effectively prevent oxygen diffusion and enhance oxygen vacancy formation, its manufacturing process may be complex and require sophisticated equipment. Simultaneously, achieving a uniform oxygen vacancy distribution may be difficult in actual manufacturing, leading to fluctuations in device performance and reliability issues. Finally, although HfO2 as a resistive switching layer has good CMOS compatibility, the overall device manufacturing process may face scalability issues in large-scale production, particularly in the precise control of the multilayer structure and the uniformity of the encapsulation layer. These factors may limit the widespread application of valence-variable memory (VRAM) resistive switching memory devices in high-performance memories.

[0049] As mentioned above, existing resistive switching memory devices typically employ a structure with four or more film layers: bottom electrode, single or multiple resistive switching layers, top electrode, and oxygen isolation layer. This results in problems such as complex structure, complex process, high manufacturing cost, and unstable performance.

[0050] This invention proposes a resistive switching memory structure and its fabrication method. By using an ohmic electrode that can achieve self-oxygen isolation, the existing resistive switching memory device with more than four film layers is simplified to three layers: bottom electrode, single-layer resistive switching layer and self-oxygen-isolated ohmic electrode (top electrode), thereby simplifying the resistive switching memory structure and reducing process complexity and manufacturing cost.

[0051] The invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0052] like Figure 5 As shown, an embodiment of the present invention provides a resistive switching memory structure, including: a bottom electrode, a resistive switching layer and a top electrode stacked sequentially from bottom to top;

[0053] The upper surface of the bottom electrode and the lower surface of the resistive switching layer are in a Schottky contact, and the lower surface of the top electrode and the upper surface of the resistive switching layer are in an ohmic contact.

[0054] The resistive switching layer is a single-layer oxide film.

[0055] The bottom electrode and the top electrode are both made of the same metal nitride. The ratio of the number of metal elements to nitrogen elements in the top electrode is greater than that in the bottom electrode. The ratio of the number of metal elements to nitrogen elements in the top electrode and the ratio of the number of metal elements to nitrogen elements in the bottom electrode each meet their respective set ratio ranges.

[0056] Specifically, because the ratio of metal to nitrogen atoms in the top electrode is larger, the oxygen affinity of the top electrode is stronger than that of the bottom electrode, making the top electrode more chemically reactive. By using metal nitrides with a larger ratio of metal to nitrogen atoms and metal nitrides with a smaller ratio of metal to nitrogen atoms as the top and bottom electrode materials, respectively, the asymmetry of oxygen affinity in the vertical direction of the device structure is achieved through improvements in the top and bottom electrode materials themselves. This asymmetry of oxygen affinity allows oxygen vacancies to move directionally during device operation, forming a stable conductive channel and achieving resistive switching behavior. Therefore, resistive switching behavior of the memory can be achieved using only a single-layer resistive switching layer, without the need for the existing multi-layer resistive switching layer structure (such as in prior art 1), thus simplifying the resistive switching layer structure. Furthermore, because the metal nitride film of the top electrode has a stronger oxygen affinity and more chemically reactive properties... More reactive, its surface can react with oxygen in the air to form metal nitride and metal oxide films. This film can prevent the top electrode film from being further oxidized in the external oxygen environment, so that the top electrode has both ohmic electrode function and self-oxygen isolation function, which can effectively prevent oxygen diffusion and make the device less susceptible to oxidation by the external oxygen environment. Therefore, the top electrode not only has good ohmic contact characteristics, but also can effectively prevent the diffusion of oxygen in the external environment, thereby protecting the structure and performance of the resistive switching layer. This allows the top electrode, a single film layer, to simultaneously accommodate both ohmic electrode and oxygen isolation functions, thus eliminating the need for the oxygen isolation layer in existing resistive switching memory (such as prior art 2). This means that the resistive switching memory device only needs three film layers: bottom electrode, resistive switching layer and top electrode to meet the device function. Compared with the traditional resistive switching memory structure with more than four film layers, the number of film layers is reduced, and the complexity and cost of the manufacturing process are reduced.

[0057] Optionally, the metal nitride forming the top and bottom electrodes can be one of titanium nitride, aluminum nitride, tungsten nitride, tantalum nitride, or zirconium nitride.

[0058] In one example, both the bottom electrode and the top electrode are made of TiN, wherein the top electrode is made of metallic TiN; the Ti / N atomic ratio in metallic TiN is preferably in the range of 1.5 to 2.5.

[0059] Specifically, the top electrode, while possessing ohmic electrode functionality, also needs to have self-oxygen isolation capabilities. This ensures the top electrode effectively prevents oxygen diffusion and is not easily oxidized by the external oxygen environment, thus protecting the structure and performance of the resistive switching layer. The selection and design of this electrode material are crucial to this invention. Specifically, for TiN materials, a higher Ti / N ratio results in a greater oxygen affinity and more active electrochemical properties (i.e., metallic TiN), making it more suitable for use as an ohmic electrode; a lower Ti / N ratio results in a lower oxygen affinity and more stable electrochemical properties (i.e., poisoned TiN), making it more suitable for use as a bottom electrode. Therefore, this invention uses TiN materials with a Ti / N atomic ratio ranging from 1.5 to 2.5 as the top electrode. Because the metallic TiN film of the top electrode has a relatively high Ti / N atomic ratio, the top electrode exhibits stronger oxygen affinity and more active chemical properties, and its surface can react with oxygen in the air to form TiNO. x and TiO x Thin film, this TiNO x and TiO x The thin film can prevent the TiN film surface from being further oxidized in the external oxygen environment, so that the top electrode has the function of ohmic electrode and self-oxygen isolation function, effectively preventing oxygen diffusion and making the device less susceptible to oxidation by the external oxygen environment. Therefore, the top electrode of metallic TiN not only has good ohmic contact characteristics, but also can effectively prevent the diffusion of oxygen in the external environment, thereby protecting the structure and performance of the resistive switching layer. This allows the top electrode, a single film layer, to simultaneously have both ohmic electrode and oxygen isolation functions, without the need to use the oxygen isolation layer (i.e., encapsulation layer) in the resistive switching memory structure of the prior art 2.

[0060] In one example, the bottom electrode is made of poisoned TiN, and the Ti / N atom ratio in the poisoned TiN is preferably in the range of 0.9 to 1.

[0061] Specifically, using poisoned TiN material with a Ti / N atomic ratio ranging from 0.9 to 1 as the bottom electrode results in a lower oxygen affinity and more stable electrochemical properties compared to the top electrode. It also forms a stable Schottky contact with the oxide insulating layer, meeting the performance requirements of the bottom electrode. By employing metallic TiN and poisoned TiN as the top and bottom electrode materials, respectively, improvements to the materials themselves can achieve oxygen affinity asymmetry in the vertical direction of the device structure. This asymmetry allows oxygen vacancies to move directionally during device operation, forming stable conductive channels and achieving resistive switching behavior.

[0062] In one example, the resistive switching layer is preferably made of tantalum oxide (TaOx) or hafnium oxide (HfOx).

[0063] Specifically, the resistive switching layer uses a single tantalum oxide or hafnium oxide film layer. Resistive switching memory devices using hafnium oxide or tantalum oxide as the resistive switching layer can achieve sub-nanosecond switching speeds and speeds exceeding 10 Hz in TaOx. 12 Extremely high cycle durability.

[0064] In existing resistive switching memories, when both the top and bottom electrodes are made of TiN material, the intermediate resistive switching layer typically requires a multilayer or intercalation structure to provide sufficient switching characteristics or stability. This is because a single oxide resistive switching layer film may not meet the performance requirements in this case. However, this invention uses TiN material with a Ti / N atomic ratio ranging from 0.9 to 1 as the bottom electrode, which has low oxygen affinity and stable electrochemical properties, and uses TiN material with a Ti / N atomic ratio ranging from 1.5 to 2.5 as the top electrode, which has a higher oxygen affinity than the bottom electrode and is less susceptible to oxidation by the external oxygen environment. By using the materials of the top and bottom electrodes, an asymmetry in oxygen affinity in the vertical direction of the device structure is achieved. This asymmetry allows oxygen vacancies to move directionally during device operation, forming a stable conductive channel and realizing resistive switching behavior. Therefore, a single tantalum oxide or hafnium oxide film layer can meet the device performance requirements, simplifying the film structure of the resistive switching layer and realizing a resistive switching memory with only a three-film structure. This design simplifies the structure of variable resistive memory while maintaining high performance and high reliability.

[0065] like Figure 5 As shown, by employing the aforementioned self-oxygen-isolated ohmic electrode and corresponding bottom electrode, and selecting a single film material for the intermediate oxide layer, a resistive switching memory with only three film layers is realized. This type of resistive switching memory has a simplified structure, and each film layer has a single material composition. The top electrode is metallic TiN, the bottom electrode is poisoned TiN, and the resistive switching layer material is either tannin oxide (Ta2O5) or hafnium oxide (HfO2). This structure of the resistive switching memory can still perform the function of a resistive switching memory, namely, bipolar switching operation (Set; Reset). The switching principle of the device is as follows: The resistive switching memory is initially in a high-resistance state; the bottom electrode is grounded. When a positive voltage is applied to the top electrode (ohmic electrode), due to the electric field and the relatively more active chemical properties of the top electrode compared to the bottom electrode, oxygen ions (negatively charged, O2O5) in the resistive switching layer... 2-The oxygen ions react with the top electrode and are "stored" within it, leaving positively charged oxygen vacancies in the intermediate resistive switching layer. When the distribution of these oxygen vacancies allows the upper and lower electrodes to connect, a conductive filament is formed, and the resistive switching memory exhibits a low-resistance state. This transition from a high-resistance state to a low-resistance state is called "set." With the bottom electrode grounded, when a negative voltage is applied to the top electrode (ohmic electrode), the oxygen ions "stored" within it are released back into the resistive switching layer under the influence of the electric field. However, due to the inert chemical properties of the bottom electrode, they do not readily react with it under the influence of the electric field. At this point, the conductive filament breaks, and the resistive switching memory again exhibits a high-resistance state. This transition from a low-resistance state to a high-resistance state is called "reset."

[0066] This three-layer resistive switching memory has two stable configurations (high resistance state and low resistance state) and has a bipolar switching function (positive voltage turns it on, negative voltage turns it off).

[0067] In one example, the surface of the top electrode and the bottom electrode near the resistive switching layer is an oxygen diffusion region. Preferably, the thickness of the oxygen diffusion region of the top electrode is 2.7 to 3.3 times the thickness of the oxygen diffusion region of the bottom electrode.

[0068] Specifically, the TiN thin films of the top and bottom electrodes exchange oxygen with the resistive switching layer (tantalum oxide or hafnium oxide) on the side near the oxide layer interface. This region is the oxygen diffusion region of the TiN thin film. The larger the oxygen diffusion region, the stronger the oxygen affinity of the TiN thin film. Therefore, to ensure the switching performance of the device, the quantitative requirement for the oxygen affinity of the TiN electrodes used as top and bottom electrodes is that the length of the oxygen diffusion region of the top electrode is about 3 times the length of the oxygen diffusion region of the bottom electrode, preferably within the range of 2.7 to 3.3 times.

[0069] In one example, the thickness of the resistive switching layer is positively correlated with the device area of ​​the resistive switching memory.

[0070] Specifically, the thickness of the oxide film in the resistive switching layer is positively correlated with the device area. Larger device areas are more prone to leakage current and the oxide film is more easily broken down, thus requiring a thicker film. For example, the cell area of ​​a memory device is 100*100μm. 2 Therefore, the thickness of the oxide resistive switching layer of the device should be greater than 15nm, preferably 15nm to 20nm, in order to prevent electrical breakdown of the device and reduce leakage current.

[0071] In one example, the thickness of the top electrode is more than twice the thickness of the resistive switching layer.

[0072] Specifically, the choice of oxygen affinity difference between the top and bottom electrodes is related to the thickness of the storage medium (resistive switching layer). A thicker storage medium makes the device more difficult to turn on, requiring a larger difference in oxygen affinity between the top and bottom electrodes; conversely, a thinner storage medium makes the device more difficult to turn off, requiring a smaller difference in oxygen affinity. This is because the difference in oxygen affinity between the top and bottom electrodes is highly dependent on the concentration of oxygen vacancies in the storage medium. A larger difference results in a higher oxygen vacancy concentration, making the device easier to turn on but harder to turn off. The top electrode acts as an "oxygen reservoir," absorbing oxygen ions to form conductive filaments composed of oxygen vacancies in the dielectric layer. To achieve effective "oxygen storage," the thickness of the ohmic electrode should generally be more than twice the thickness of the storage medium layer. The bottom electrode thickness has fewer requirements; to simplify the process, it is preferred to have the same thickness as the top electrode. For example, the device cell area of ​​a memory is 100*100μm. 2 If the thickness of the resistive switching layer is 15nm to 20nm, then the thickness of both the top electrode and the bottom electrode can be selected as 50nm.

[0073] In one example, the top electrode and the resistive switching layer are patterned films, with the top electrode connected to a voltage source and the bottom electrode grounded; the bottom electrode is located on the substrate. The complete structure of the resistive switching memory device is as follows: Figure 6 As shown.

[0074] Similarly, in other embodiments, other metal nitride materials such as aluminum nitride, tungsten nitride, tantalum nitride, and zirconium nitride can also be used as the top electrode and bottom electrode materials. In this case, the atomic ratio of metal elements (aluminum, tungsten, tantalum, zirconium, etc.) to nitrogen elements in the metal nitride film of the top electrode needs to be greater than that in the metal nitride film of the bottom electrode. The atomic ratio of metal elements to nitrogen elements in the metal nitride films of the top and bottom electrodes should be controlled to meet a certain range to ensure that the top electrode has good ohmic contact characteristics while also having a certain self-oxygen isolation capability. At the same time, a suitable film thickness should be selected according to the area of ​​the device to ensure that the oxygen affinity of the top electrode and the oxygen affinity of the bottom electrode reach a certain difference, thus ensuring the switching characteristics of the memory.

[0075] like Figure 7 As shown, this embodiment of the invention also provides a method for manufacturing a resistive variable memory structure, including:

[0076] S1: A metal nitride film is deposited on a substrate to form a bottom electrode; a monolayer oxide film is deposited on the bottom electrode to form a resistive switching layer; a metal nitride film is deposited on the resistive switching layer to form a top electrode; wherein the bottom electrode and the top electrode are made of the same metal nitride, and the atomic ratio of metal elements to nitrogen elements in the top electrode is greater than the atomic ratio of metal elements to nitrogen elements in the bottom electrode.

[0077] Optionally, the metal nitride is one of titanium nitride, aluminum nitride, tungsten nitride, tantalum nitride, and zirconium nitride.

[0078] Preferably, the bottom electrode, resistive switching layer, and top electrode are formed using reactive magnetron sputtering. Taking TiN as an example where both the bottom and top electrodes are made of TiN (poisoned TiN for the bottom electrode and metallic TiN for the top electrode), the nitrogen flow rate used when forming the top electrode is preferably 10–20 sccm; the nitrogen flow rate used when forming the bottom electrode is preferably 100–120 sccm. The resistive switching layer can be made of tantalum oxide or hafnium oxide.

[0079] Specifically, in existing resistive switching memories, when both the top and bottom electrodes are made of TiN material, the intermediate resistive switching layer typically requires a multilayer or intercalated structure to provide sufficient switching characteristics or stability. This is because a single oxide resistive switching layer film may not meet the performance requirements in this case. However, by utilizing magnetron reactive sputtering technology, the stoichiometry of the TiN film can be continuously adjusted. Specifically, the larger the Ti / N ratio, the greater the oxygen affinity of TiN, and the more electrochemically active it is (i.e., metallic TiN), making it more suitable as an ohmic electrode; the smaller the Ti / N ratio, the lower the oxygen affinity of TiN, and the more electrochemically stable it is (i.e., poisoned TiN), making it more suitable as a bottom electrode. Therefore, by precisely controlling the stoichiometry of the TiN film, a TiN ohmic electrode with a greater oxygen affinity than the bottom electrode and less susceptible to oxidation by the external oxygen environment can be prepared.

[0080] The feasibility analysis process for a self-oxygen-isolated ohmic electrode is as follows: Figure 4 As shown, firstly as Figure 4 On the left, poisoned TiN material is used as the bottom electrode (Ti / N ratio of 0.9-1), tantalum oxide is used as the resistive switching layer, pure Ti material is used as the ohmic electrode, and TiN material is used as the oxygen isolation layer (for ease of representation, the oxygen isolation layer TiN material is referred to as TiN). x (i.e., the Ti / N ratio is set to 1:x). Based on magnetron reactive sputtering technology, through multiple experiments, the N content in the oxygen isolation layer TiN material was gradually reduced to find the minimum N content that can satisfy the oxygen isolation function, i.e., reducing the TiN content. x Find the minimum value of x that satisfies the oxygen isolation function of TiN. min This allows us to determine the Ti / N ratio range (x value range) of TiN materials capable of functioning as oxygen-barrier layers, and subsequently, the Ti / N atomic ratio range of TiN materials capable of functioning as oxygen-barrier layers; then, as... Figure 4 In the middle, the N content in the oxygen barrier TiN material is fixed at the previously determined minimum value, i.e., TiNxmin And TiN material is used as the ohmic electrode, i.e., TiN y By gradually increasing the nitrogen content in the TiN ohmic electrode material, i.e., increasing the y value, the maximum nitrogen content required to satisfy the ohmic contact performance of the TiN ohmic electrode can be found. y Find the maximum value of y that satisfies the performance requirements of the ohmic electrode. min This allows us to determine the Ti / N ratio range (i.e., the y-value range) of TiN materials that can serve as ohmic electrodes, and further determine the Ti / N atomic ratio range of TiN materials that can achieve ohmic electrode functionality; finally, as... Figure 4 As shown on the right, based on the previously determined Ti / N ratio ranges for TiN materials that satisfy the oxygen barrier function and the Ti / N ratio ranges for TiN materials that satisfy the ohmic electrode function, the overlapping region of these two Ti / N ratio ranges was found, thus determining the Ti / N ratio range for TiN materials that simultaneously satisfy the ohmic electrode function and the self-oxygen barrier function. Analysis determined that the Ti / N ratio range for TiN materials meeting these conditions is 1.5–2.5.

[0081] The TiN material (Ti / N ratio ranging from 1.5 to 2.5) obtained from the above feasibility analysis is used as the top electrode. This top electrode not only has the function of an ohmic electrode but also has a self-oxygen isolation function. In this way, the top electrode can effectively prevent oxygen diffusion and is not easily oxidized by the external oxygen environment, thereby protecting the structure and performance of the resistive switching layer. The selection and design of this electrode material is the key to this invention.

[0082] In specific implementation, by controlling the atomic ratio of Ti to N elements within the range of 1.5–2.5 during TiN deposition using magnetron reactive sputtering, a metallic TiN thin film is formed. This results in a TiN ohmic electrode with a higher oxygen affinity than the bottom electrode and is less susceptible to oxidation by the external oxygen environment, thus creating a self-oxygen-isolated ohmic electrode. This electrode not only possesses excellent ohmic contact characteristics but also effectively prevents oxygen diffusion, thereby protecting the structure and performance of the resistive switching layer. This design simplifies the structure of the variable resistor memory while maintaining high performance and high reliability. Similarly, by controlling the atomic ratio of Ti to N elements within the range of 0.9–1 during TiN deposition using magnetron reactive sputtering, a poisoned TiN thin film is formed, resulting in a bottom electrode with low oxygen affinity and stable electrochemical properties.

[0083] In a specific example, a reactive magnetron sputtering process is used on a substrate ( On a SiO2 insulating layer / 400μm Si substrate, poisoned TiN (approximately 50nm), a resistive switching layer (tantalum oxide between 15-20nm), and metallic TiN (approximately 50nm) are deposited sequentially from bottom to top, forming a three-layer structure. The nitrogen flow rate process parameters for magnetron reactive sputtering of metallic TiN are 15 sccm, and the atomic ratio of titanium to nitrogen is approximately 2.46. The nitrogen flow rate process parameters for magnetron reactive sputtering of poisoned TiN are 110 sccm, and the atomic ratio of titanium to nitrogen is approximately 0.96.

[0084] Similarly, in other embodiments, if other metal nitride materials such as aluminum nitride, tungsten nitride, tantalum nitride, and zirconium nitride are used as the top electrode and bottom electrode materials, magnetron reactive sputtering can be used to adjust the atomic ratio of metal elements (aluminum, tungsten, tantalum, zirconium, etc.) to nitrogen in the metal nitride film to produce top and bottom electrodes that meet the requirements. The atomic ratio of metal elements to nitrogen in the metal nitride film of the top electrode is greater than that in the metal nitride film of the bottom electrode. The range of the atomic ratio of metal elements to nitrogen in the metal nitride films of the top and bottom electrodes is determined to ensure that the oxygen affinity of the top electrode and the bottom electrode have a certain difference. This satisfies the requirement that the top electrode has good ohmic contact characteristics while also having a certain self-oxygen isolation capability. The appropriate film thickness is selected according to the area of ​​the device to ensure the switching characteristics of the memory.

[0085] S2: A patterned photoresist layer is formed on the top electrode;

[0086] Specifically, a patterned photoresist layer is formed on the structural layer prepared in step S1 by photolithography.

[0087] S3: Using a patterned photoresist layer as a mask, the top electrode layer and resistive switching layer are etched by a dry etching process to complete the patterning of the top electrode and resistive switching layer.

[0088] Specifically, the pattern is transferred to the top electrode and resistive switching layer by using the photoresist layer in step S2 as an etching mask through chloride ion dry etching.

[0089] S4: Remove the photoresist layer.

[0090] Specifically, the photoresist is removed by soaking in acetone (for 15 minutes). Finally, through the above steps, a three-layer resistive switching memory structure is realized, with a cross-section as shown... Figure 8 As shown.

[0091] Furthermore, after the memory structure is fabricated, the oxygen affinity of the top and bottom electrodes can be determined by depth-direction SIMS (secondary ion mass spectrometry) analysis of the electrode films deposited on the silicon oxide substrate. Figure 9aThe image shows the secondary ion mass spectrometry (SIMS) characterization of metallic TiN (N2 = 15 sccm). Figure 9b This is a secondary ion mass spectrometry (SIMS) characterization of poisoned TiN (N2 = 110 sccm).

[0092] Focus on the concentration distribution of four elements, Ti, N, O, and Si, along the depth (thickness) direction of the thin film. Figure 9a and Figure 9b The zero point on the horizontal axis represents the sample surface; increasing the horizontal axis value corresponds to measuring the elemental distribution at a deeper depth in the sample. Observing the concentration distribution of Si element, we can find... Figure 9a The TiN / SiO2 interface appears at a depth of 44 nm. Figure 9b At 49 nm, marked by a dashed line in the figure, the left side represents the metallic TiN film, and the right side represents the SiO2 oxide layer. Observing the concentration distribution of oxygen in the TiN film, it can be seen that the oxygen concentration first decreases and then increases from the film surface. The high oxygen content on the TiN film surface is due to the reaction of TiN with oxygen in the air to form TiNOx and TiOx films, and this oxide film can prevent the TiN film surface from being further oxidized in the external oxygen environment. The oxygen concentration in the TiN film increases again near the TiN / SiO2 interface because there is oxygen exchange between TiN and SiO2; this region is the oxygen diffusion region near the oxide layer interface in the TiN film. The larger the oxygen diffusion region, the stronger the oxygen affinity of the TiN film.

[0093] like Figure 9a As shown, the O element concentration increases again from a depth of 30 nm. The oxygen diffusion region is marked with a gray area, and the length of the diffusion region is 15.2 nm. Figure 9b The oxygen diffusion region near the oxide layer interface of poisoned TiN is also marked in gray, with a diffusion region length of 5.6 nm. The oxygen diffusion region length of metallic TiN is 2.7 times that of poisoned TiN, which is sufficient to prove that the former has a much greater oxygen affinity than the latter.

[0094] Therefore, to ensure the switching performance of the device, the quantitative requirement for the oxygen affinity of TiN electrodes as both top and bottom electrodes is that the length of the oxygen diffusion region of the top electrode is about 3 times that of the bottom electrode, preferably in the range of 2.7 to 3.3 times.

[0095] For the poisoned TiN used as the bottom electrode, the Ti / N atomic ratio should be close to but less than 1, preferably in the range of 0.9 to 1. For the metallic TiN used as the top electrode, the Ti / N atomic ratio should be in the range of 1.5 to 2.5.

[0096] Furthermore, the thickness of the oxide film serving as the resistive switching layer in resistive switching memory devices is related to the device area. Larger areas are more prone to leakage current and the oxide film is more easily broken down, thus requiring a thicker film. The ohmic electrode, also known as the top electrode, acts as an "oxygen reservoir" to absorb oxygen ions, and its thickness should be more than twice the thickness of the resistive switching layer. The bottom electrode has fewer requirements regarding thickness.

[0097] The choice of oxygen affinity difference between the top and bottom electrodes is also related to the thickness of the resistive switching layer. A thicker resistive switching layer makes the device more difficult to turn on, requiring a greater difference in oxygen affinity between the top and bottom electrodes; conversely, a thinner resistive switching layer makes the device more difficult to turn off, requiring a smaller difference in oxygen affinity between the top and bottom electrodes. This is because the difference in oxygen affinity between the top and bottom electrodes is highly dependent on the concentration of oxygen vacancies in the resistive switching layer. A greater difference results in a higher oxygen vacancy concentration, making the device easier to turn on but harder to turn off. Therefore, the resistive switching layer thickness should first be determined based on the device area to define a minimum range, preventing electrical breakdown and reducing leakage current effects. The specific thickness should be further optimized based on the selection of the top and bottom electrode materials.

[0098] In this embodiment, the fabricated device unit area is 100*100μm. 2 The thickness of the resistive switching layer should be greater than 15 nm to prevent electrical breakdown and reduce leakage current. Since both the top and bottom electrodes are made of TiN, a very large difference in oxygen affinity cannot be achieved simply by adjusting the stoichiometry. Therefore, to ensure normal switching, the dielectric layer thickness should be kept as low as possible. The preferred resistive switching layer thickness is 15-20 nm. The top electrode TiN film, acting as an ohmic electrode, plays a "storage" role. It needs to absorb oxygen ions from the storage medium in the resistive switching layer, thereby forming oxygen vacancies to create conductive filaments. To achieve effective "storage," the ohmic electrode thickness should generally be more than twice the thickness of the storage medium layer. In this embodiment, both the ohmic and bottom electrode thicknesses are 50 nm.

[0099] Furthermore, the electrical performance of the resistive switching memory device fabricated in this embodiment was tested. The film structure of the resistive switching memory fabricated in this embodiment is as follows: a top electrode of metallic TiN (50 nm thick), a resistive switching layer of tantalum oxide (Ta2O5) material (15-20 nm thick), and a bottom electrode of poisoned TiN (50 nm thick), i.e., TiN / TaO. x / TiN structure.

[0100] TiN / TaO xThe initial state of the / TiN structure resistive switching memory is high resistance. First, a forward forming test is performed. The forming test is a crucial step in memristor development, primarily used to activate the resistive switching characteristics of the device and verify its functional reliability. This involves applying a positive voltage to the top electrode and grounding the bottom electrode, then applying a specific voltage or current pulse to transition the memristor from a high resistance state (HRS) to a low resistance state (LRS), completing the initial activation. The test voltage is incremented in steps from 0 to 3.5V and then back, and the current flowing through the resistive switching memory is measured. During this test, the current is limited to within 1mA.

[0101] like Figure 10 As shown, when the forward voltage increases to 3.3V, the resistance of the resistive random access memory (IRRAM) changes abruptly, jumping from the initial high-resistance state (HRS) to the low-resistance state (LRS). The method for reading the resistance of the IRRAM involves applying a read voltage across the device and measuring the current flowing through it; the resistance is then the ratio of voltage to current. Small read voltage values, such as 0.3V, will not cause a change in the IRRAM's state. After the forming test, the resistance of this IRRAM is 1.2kΩ, while the initial high-resistance state resistance before the forming test was 290kΩ, indicating a successful forward forming test.

[0102] During the reverse forming test, a negative voltage is applied to the top electrode, and the bottom electrode is grounded. The test voltage is stepped from 0 to -3.5V and back, and the current through the resistive switching memory is measured. The current is limited to 1mA during this test. Figure 10 As shown, the reverse Forming test cannot cause the initial high-resistivity state of this resistive random access memory to change its configuration, and the reverse Forming test fails.

[0103] After the Forming test, the device underwent IV curve testing. During the Set test, a positive voltage was applied to the top electrode, and the bottom electrode was grounded. The test voltage was increased in steps from 0 to 3.5V and then returned, and the corresponding current value through the resistive switching memory was measured. The current was limited to within 10mA during this test. It was observed that when the test voltage increased to 2.7V, the resistance of the resistive switching memory jumped from a high-resistance state to a low-resistance state, as shown below. Figure 11 As shown, the high-resistance state reading before Set is 3.8kΩ, and the low-resistance state reading after Set is 210Ω. The ratio of the high-resistance state to the low-resistance state, which is the switching ratio of the resistive variable memory during the Set process, is 18.

[0104] like Figure 10 As shown, the TiN / TaO in this embodiment xThe fact that the / TiN structure resistive switching memory can only be formed in the forward direction and not in the reverse direction proves that the switching mode of this structure is a bipolar switch and that there is an asymmetric structure of oxygen affinity. Since the film structure of this device is symmetrical, the asymmetry of oxygen affinity comes entirely from the difference in oxygen affinity between the metallic TiN top electrode and the poisoned TiN bottom electrode, thus proving that the design optimization of the electrode materials was successful.

[0105] from Figure 11 The IV curve shown indicates that this resistive switching memory uses a bipolar switching mode, i.e., V Set With V Reset The polarity is opposite, consistent with the Forming test results. The device at V Set With V Reset The significant resistance jump indicates that the conductive filaments within the storage dielectric layer of this device are directionally grown. The device exhibits relatively stable resistance at low read voltages, demonstrating the stability of the conductive filaments; only when the voltage reaches V... Reset The conductive filaments only break when the oxygen vacancies are present. The test results show that the conductive filaments composed of oxygen vacancies grow in a directional and stable manner, indicating that the electrode material and device structure design of the resistive switching memory are both successful.

[0106] In summary, the beneficial effects of the present invention are as follows:

[0107] ① Simplified device structure: By using a self-oxygen-isolated ohmic electrode, the oxygen isolation layer can be removed, simplifying the traditional four-layer or more structure to a three-layer structure. This reduces the number of film layers and lowers the complexity of the manufacturing process. This simplified structure not only reduces material usage but also reduces manufacturing steps, thereby lowering manufacturing costs.

[0108] ② Reduced manufacturing costs: The simplified structure reduces material usage and manufacturing steps, thus significantly lowering manufacturing costs. Furthermore, the reduced number of membrane layers simplifies process control, further improving production efficiency.

[0109] ③ High performance retention: By precisely controlling the stoichiometry of the TiN thin film through reactive magnetron sputtering, the dual functions of top electrode oxygen isolation and ohmic contact are achieved. This design ensures that the device maintains good resistive switching characteristics and stability while simplifying the structure, meeting the requirements of high-performance memory.

[0110] ④ Improved uniformity in high-integration applications: Simplified structure helps improve the uniformity of devices in high-integration applications, reducing process variations and performance fluctuations caused by multi-layer structures. This uniformity is crucial for mass production and high-density memory applications. This design is not only applicable to current memory technologies but also lays the foundation for future higher-density memory technologies.

[0111] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A resistive variable memory structure, characterized in that, include: The bottom electrode, resistive switching layer, and top electrode are stacked sequentially from bottom to top; The upper surface of the bottom electrode and the lower surface of the resistive switching layer are in a Schottky contact, and the lower surface of the top electrode and the upper surface of the resistive switching layer are in an ohmic contact. The resistive switching layer is a single-layer oxide film. The bottom electrode and the top electrode are both made of the same metal nitride, and the ratio of the number of metal elements to nitrogen elements in the top electrode is greater than that in the bottom electrode. The top electrode has a stronger oxygen affinity than the bottom electrode, and the top electrode has a self-oxygen isolation function. The metal nitride is titanium nitride, and the Ti / N atomic ratio in the TiN material of the top electrode ranges from 1.5 to 2.

5.

2. The resistive switching memory structure according to claim 1, characterized in that, The Ti / N atomic ratio in the TiN material of the bottom electrode ranges from 0.9 to 1.

3. The resistive switching memory structure according to claim 1, characterized in that, The surfaces of the top electrode and the bottom electrode near the resistive switching layer are oxygen diffusion regions, and the thickness of the oxygen diffusion region of the top electrode is 2.7 to 3.3 times the thickness of the oxygen diffusion region of the bottom electrode.

4. The resistive switching memory structure according to claim 1, characterized in that, The thickness of the resistive switching layer is positively correlated with the device area of ​​the resistive switching memory.

5. The resistive switching memory structure according to claim 4, characterized in that, The thickness of the top electrode is more than twice the thickness of the resistive switching layer.

6. The resistive switching memory structure according to claim 1, characterized in that, The resistive switching layer is made of tantalum oxide or hafnium oxide.

7. A method for manufacturing a resistive switching memory structure as described in any one of claims 1-6, characterized in that, include: A metal nitride film is deposited on the substrate to form the bottom electrode; A single-layer oxide film is deposited on the bottom electrode to form a resistive switching layer; A metal nitride film is deposited on the resistive switching layer to form a top electrode; The bottom electrode and the top electrode are both made of the same metal nitride. The ratio of the number of metal elements to nitrogen atoms in the top electrode is greater than that in the bottom electrode. The oxygen affinity of the top electrode is stronger than that of the bottom electrode, and the top electrode has a self-oxygen isolation function. The metal nitride is titanium nitride, and the Ti / N atomic ratio in the TiN material of the top electrode ranges from 1.5 to 2.

5.

8. The manufacturing method according to claim 7, characterized in that, The bottom electrode, the resistive switching layer, and the top electrode are formed using reactive magnetron sputtering.

9. The manufacturing method according to claim 8, characterized in that, The Ti / N atom ratio in the TiN material of the bottom electrode ranges from 0.9 to 1; The nitrogen flow rate used in forming the top electrode is 10~20 sccm; The nitrogen flow rate used in forming the bottom electrode is 100~120 sccm.

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