Memory cell, memory array, memory, electronic device and preparation method

Abstract

A memory cell, a memory array, a memory, an electronic device and a preparation method. The memory cell comprises: a lower electrode, composite resistive-switching layers and an upper electrode, which are sequentially arranged, wherein the number of the composite resistive-switching layers is greater than 2; and a standard reduction potential of each of the composite resistive-switching layers is less than 0 and decreases layer by layer in a first direction, which first direction is the direction from the lower electrode to the upper electrode. In the memory cell, composite resistive-switching layers, which have standard reduction potentials varying gradually layer by layer, can form a virtual path for guiding oxygen vacancy migration in a layer stacking direction, thereby guiding the generation and migration of oxygen vacancies, and controlling the distribution of the oxygen vacancies in the composite resistive-switching layers. Therefore, the distribution of the oxygen vacancies in the composite resistive-switching layers has a certain regularity and uniformity, thus improving the performance and reliability of a non-volatile memory device.

Description

Storage cell, storage array, memory, electronic device and its fabrication method Cross-reference to related applications

[0001] This application claims priority to Chinese patent application filed on April 16, 2025, with application number 202510484313.7 and entitled "Memory cell, memory array, memory, electronic device and method of preparation". Technical Field

[0002] This disclosure generally relates to the field of semiconductor technology. More specifically, this disclosure relates to a non-volatile two-terminal memory cell, a memory array, a memory, an electronic device, and a method for fabricating a non-volatile two-terminal memory cell. Background Technology

[0003] Resistive Random Access Memory (RRAM) is a non-volatile storage device that stores data by changing the resistance state of the storage cells. Due to its advantages such as high-speed read and write, low power consumption, high-density integration and good scalability, it is currently widely used in the fields of Internet of Things, artificial intelligence chips, wearable electronic devices and next-generation computing architectures.

[0004] Based on the formation method of the conductive filaments in the resistive switching layer of RRAM, the mainstream technical routes can be divided into two types: the oxygen-hole method of Oxide-Resistive Random-Access Memory (OxRAM) and the conductive filament method of Conductive Bridging Random-Access Memory (CBRAM). In the oxygen-hole method of OxRAM, the conductive filaments in the resistive switching layer are formed by oxygen vacancies. In the resistive switching layer, the absence of oxygen atoms forms oxygen vacancies. By applying a voltage, oxygen vacancies can move in the resistive switching layer and can act as charge carriers, affecting the conductivity of the material.

[0005] The stability and uniformity of oxygen vacancies are crucial for the reliability of data retention in non-volatile storage devices. However, controlling oxygen vacancies is difficult, and non-uniformity in oxygen vacancies distribution can affect the characteristics of resistive switching, including SET / RESET voltage, current, and resistive switching window, thereby affecting the performance and reliability of non-volatile storage devices.

[0006] In view of this, there is an urgent need to provide a non-volatile two-terminal storage cell that can improve the problem of uneven oxygen vacancy distribution in oxygen-hole RRAM, thereby achieving higher performance stability and reliability. Summary of the Invention

[0007] In order to address at least one or more of the technical issues mentioned above, this disclosure proposes a non-volatile end-to-end storage solution in several aspects.

[0008] In a first aspect, this disclosure provides a non-volatile two-terminal storage cell comprising: a lower electrode, a composite resistive switching layer, and an upper electrode arranged sequentially; wherein the number of layers in the composite resistive switching layer is greater than 2; the standard reduction potential of each layer in the composite resistive switching layer is less than 0 and decreases layer by layer along a first direction, the first direction being the direction from the lower electrode to the upper electrode.

[0009] In some embodiments, the composite resistive switching layer includes: a first resistive switching layer, a second resistive switching layer, and a third resistive switching layer disposed along a first direction; the first resistive switching layer includes a first metal oxide, the second resistive switching layer includes a second metal and / or a second metal oxide, and the third resistive switching layer includes a third metal and / or a third metal oxide, wherein the standard reduction potential of the third metal and / or the third metal oxide is less than or equal to -0.8V.

[0010] In some embodiments, the second metal oxide is an oxide formed by the redox reaction of the second metal with the first resistive switching layer.

[0011] In some embodiments, the first resistive switching layer includes: multiple first sub-resistive switching layers disposed along a first direction, wherein the number of oxygen atoms in each first sub-resistive switching layer decreases layer by layer along the first direction; and / or, the third resistive switching layer includes: multiple third sub-resistive switching layers disposed along the first direction, wherein the number of oxygen atoms in each third sub-resistive switching layer decreases layer by layer along the first direction.

[0012] In some embodiments, in the multilayer third sub-resistive switching layer, the third sub-resistive switching layer in contact with the upper electrode is made of a third metal.

[0013] In some embodiments, the first metal includes one or more of the following metals: hafnium (Hf), titanium (Ti), and tantalum (Ta); the third metal includes one or more of the following metals: hafnium (Hf), tantalum (Ta), titanium (Ti), and aluminum (Al), and the first metal has a lower metallic activity than the third metal; the second metal includes one or more of the following metals: hafnium (Hf), titanium (Ti), and tantalum (Ta).

[0014] In some embodiments, the first metal is M1, M1∈{Hf, Ti, Ta}, and the first metal oxide is M1Ox; the third metal is M3, M3∈{Hf, Ta, Ti, Al}, and the third metal oxide is M3Or; the second metal is M1 or M3, and the second metal oxide is M1Oy or M3Oz, wherein the value of y is less than x, and the value of z is greater than r.

[0015] In some embodiments, M1 is Hf, and the value range of x is (1.0, 2.0], and the value range of y is [1.0, 2.0); M3 is Ta, and the value range of z is [1.0, 2.5].

[0016] In some embodiments, if the second resistive switching layer comprises a second metal, the thickness of the second resistive switching layer is less than or equal to 5 nm; if the second resistive switching layer comprises a second metal oxide, the thickness of the second resistive switching layer is in the range of [2,8] nm.

[0017] In some embodiments, if the second resistive switching layer includes a second metal oxide and the second metal is Hf, the thickness of the second resistive switching layer is in the range of [3,8] nm; if the second resistive switching layer includes a second metal oxide and the second metal is Ta, the thickness of the second resistive switching layer is in the range of [2,6] nm; if the second resistive switching layer includes a second metal and the second metal is Hf, the thickness of the second resistive switching layer is less than or equal to 3 nm.

[0018] In a second aspect, this disclosure provides a storage array comprising: non-volatile dual-end storage cells as described in any of the first aspects.

[0019] In a third aspect, this disclosure provides a memory comprising: a memory array as described in the second aspect.

[0020] In a fourth aspect, this disclosure provides an electronic device including: a memory as described in the third aspect.

[0021] In a fifth aspect, this disclosure provides a method for fabricating a non-volatile two-terminal memory device, comprising: forming a lower electrode; forming a composite resistive switching layer on the lower electrode; and forming an upper electrode on the composite resistive switching layer to obtain a non-volatile two-terminal memory device; wherein the number of layers of the composite resistive switching layer is greater than 2; and the standard reduction potential of each layer of the composite resistive switching layer is less than 0 and decreases layer by layer along a first direction, the first direction being the direction from the lower electrode to the upper electrode.

[0022] In some embodiments, forming a composite resistive switching layer on the lower electrode includes: forming a first metal oxide on the lower electrode to form a first resistive switching layer; forming a second metal and / or a second metal oxide on the first resistive switching layer to form a second resistive switching layer; forming a third metal and / or a third metal oxide on the second resistive switching layer to form a third resistive switching layer and obtaining a composite resistive switching layer; wherein the standard reduction potential of the third metal and / or the third metal oxide is less than or equal to -0.8V.

[0023] In some embodiments, forming a third metal and / or a third metal oxide on a second resistive switching layer to form a third resistive switching layer includes: forming a third metal on a second resistive switching layer; in response to a preset time period, partially or completely of the third metal is converted into a third metal oxide through a redox reaction to form a third resistive switching layer; wherein the third resistive switching layer includes: multiple third sub-resistive switching layers disposed along a first direction, wherein the number of oxygen atoms in each third sub-resistive switching layer decreases layer by layer along the first direction.

[0024] In some embodiments, after a third metal is formed on the second resistive switching layer, the method further includes: in response to a preset time period, a portion of the first resistive switching layer undergoes a redox reaction to form multiple first sub-resistive switching layers disposed along a first direction, wherein the number of oxygen atoms in each first sub-resistive switching layer decreases layer by layer along the first direction.

[0025] In some embodiments, forming a second metal and / or a second metal oxide on the first resistive switching layer includes: forming a second metal with a thickness of less than or equal to 5 nm on the first resistive switching layer; or forming a second metal oxide with a thickness in the range of [2,8] nm on the first resistive switching layer.

[0026] In some embodiments, forming a second metal and / or a second metal oxide on a first resistive switching layer includes: forming a second metal on a first resistive switching layer to form a second resistive switching layer; after obtaining a non-volatile end-to-end storage device, the method further includes: oxidizing the second metal into a second metal oxide in response to performing an electrical operation for a preset duration and / or the non-volatile end-to-end storage device.

[0027] In some embodiments, before forming a third metal and / or a third metal oxide on the second resistive switching layer, the method further includes: determining a third metal and / or a third metal oxide based on a first metal oxide; before depositing a second metal and / or a second metal oxide on the first resistive switching layer, the method further includes: determining a second metal and / or a second metal oxide based on a first metal oxide and a third metal; wherein the first metal includes one or more of the following metals: hafnium, titanium, tantalum; the third metal includes one or more of the following metals: hafnium, tantalum, titanium, aluminum, and the first metal has a lower metallic reactivity than the third metal; the second metal includes one or more of the following metals: hafnium, titanium, tantalum.

[0028] The non-volatile end-to-end memory device provided above employs a resistive switching layer with a composite layer structure of two or more layers. Since the standard reduction potential of each layer in the composite layer structure gradually changes, that is, the oxidizability / oxygen absorption capacity of each layer gradually changes, a virtual path guiding the movement of oxygen vacancies is formed in the stacking direction. Oxygen atoms will move from the position with a higher standard reduction potential to the position with a lower standard reduction potential, thereby making the distribution of oxygen vacancies in the composite resistive switching layer more regular and uniform, thus improving the performance and reliability of the non-volatile memory device. Attached Figure Description

[0029] The above and other objects, features, and advantages of exemplary embodiments of this disclosure will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this disclosure are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein:

[0030] Figure 1 shows an exemplary structural diagram of a non-volatile two-ended memory cell according to some embodiments of this disclosure;

[0031] Figure 2 shows an exemplary structural diagram of a non-volatile two-ended memory cell according to some embodiments of this disclosure;

[0032] Figure 3 shows an exemplary flowchart of a method for fabricating a non-volatile two-terminal storage device according to some embodiments of this disclosure;

[0033] Figure 4 shows an exemplary flowchart of a method for preparing a third resistive switching layer according to some embodiments of this disclosure;

[0034] Figure 5 shows an exemplary flowchart of a method for fabricating a non-volatile two-terminal storage device according to some embodiments of this disclosure. Detailed Implementation

[0035] The technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, not all of them. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0036] It should be understood that the terms “comprising” and “including” used in this disclosure and claims indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0037] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this disclosure. As used in this disclosure and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this disclosure and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0038] As used in this specification and claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [described condition or event] is detected," or "in response to detection of [described condition or event]."

[0039] The specific embodiments disclosed herein will now be described in detail with reference to the accompanying drawings.

[0040] Exemplary application scenarios

[0041] Resistive Random Access Memory (RRAM) is widely used in the Internet of Things, artificial intelligence chips, wearable electronic devices and next-generation computing architectures due to its advantages such as high-speed read and write, low power consumption, high-density integration and good scalability.

[0042] The reliability of non-volatile storage devices, especially RRAM based on the OxRAM oxygen-hole method, is largely affected by the stability and uniformity of oxygen vacancies. Reducing the energy required for the movement and redistribution of oxygen vacancies helps improve the durability of RRAM, while improving the uniformity of oxygen vacancies distribution helps RRAM stably retain data and ensure data security.

[0043] However, controlling oxygen vacancies is difficult, and existing non-volatile storage devices often suffer from performance inconsistencies due to uneven distribution of oxygen vacancies. In addition, the migration of oxygen vacancies in high-temperature environments may also cause data retention problems.

[0044] Exemplary application scheme

[0045] In view of this, the present disclosure provides a non-volatile two-terminal storage solution, which forms a virtual path guiding the movement of oxygen vacancies in the stacking direction by gradually changing the standard reduction potential of the resistive switching layer of the composite structure. This improves the control over the distribution of oxygen vacancies, thereby improving the uniformity of the distribution of oxygen vacancies in the device and thus improving the performance and reliability of the non-volatile memory device.

[0046] Figure 1 shows an exemplary structural diagram of a non-volatile two-terminal memory cell according to some embodiments of the present disclosure. As shown in Figure 1, the non-volatile two-terminal memory cell includes a lower electrode 10, a composite resistive switching layer 20, and an upper electrode 30 arranged in sequence.

[0047] The lower electrode 10 and the upper electrode 30 are made of conductive materials, such as conductive nitrides of Ti, W, Ru, Ir, Ni, Pt, Cu, Ag, Au, Al, or metal / conductive nitride stacks, without much restriction here.

[0048] The resistive switching layer is the core component of the non-volatile two-terminal memory cell, which realizes data storage through resistive state switching. In the aforementioned non-volatile two-terminal memory cell, the resistive switching layer adopts a multi-layer design with a composite structure. Here, "multi-layer" refers to the number of layers in the composite resistive switching layer 20 being greater than 2. In the aforementioned composite resistive switching layer, the standard reduction potential of each layer is less than 0 and decreases layer by layer along a first direction. The first direction refers to the direction from the lower electrode to the upper electrode, which can also be understood as the layer stacking direction when fabricating the non-volatile two-terminal memory cell.

[0049] The standard reduction potential (SPP) measures a substance's tendency to gain electrons under standard conditions, i.e., its tendency to be reduced. These standard conditions include 25°C, 1 atm, and a 1 M concentration. The SPP is referenced to the standard hydrogen electrode, whose potential is defined as 0 V. The SPP is usually expressed as a negative number. A smaller SPP indicates that the substance more easily loses electrons and thus more easily combines with oxygen atoms, meaning it is more easily oxidized, has stronger reducing power, and is more prone to oxidation reactions. Conversely, a larger SPP indicates that the substance is less likely to lose electrons, is more easily reduced, has stronger oxidizing power, and is more prone to reduction reactions.

[0050] In this disclosed embodiment, since the standard reduction potential of each layer in the composite resistive switching layer decreases layer by layer along the first direction, the structural layer near the upper electrode in the composite resistive switching layer is more likely to absorb oxygen from the structural layer near the lower electrode, thereby generating oxygen vacancies or oxygen holes in the structural layer near the lower electrode. This forms a virtual path that can guide the distribution of oxygen vacancies or oxygen holes, improving the controllability of the distribution of oxygen vacancies or oxygen holes, and thus improving the performance and reliability of non-volatile memory devices.

[0051] In some embodiments, as shown in FIG1, the composite resistive switching layer 20 includes at least three structural layers, specifically including: a first resistive switching layer 21, a second resistive switching layer 22, and a third resistive switching layer 23 disposed along a first direction. According to the description in the preceding embodiments, the standard reduction potentials of the first resistive switching layer 21, the second resistive switching layer 22, and the third resistive switching layer 23 decrease progressively. Therefore, among the three structural layers, the third resistive switching layer is the most easily oxidized, readily absorbing oxygen from the first and second resistive switching layers. The second resistive switching layer is less easily oxidized, readily absorbing oxygen from the first resistive switching layer. The first resistive switching layer is the least easily oxidized, serving to provide oxygen atoms required for the oxidation reactions of the second and third resistive switching layers. Functionally, the first resistive switching layer can be understood as an oxygen-rich layer, the second resistive switching layer as a buffer layer or transition layer, and the third resistive switching layer as an oxygen-absorbing layer.

[0052] As an example, assume the first resistive switching layer is HfO2, the second resistive switching layer is Hf, and the third resistive switching layer is Ta. The second resistive switching layer can absorb oxygen from the first resistive switching layer and undergo an oxidation reaction, thus oxidizing the second resistive switching layer from Hf to unsaturated hafnium oxide. The first resistive switching layer undergoes a reduction reaction, reducing the saturated hafnium oxide to unsaturated hafnium oxide and generating certain oxygen vacancies or oxygen holes. The third resistive switching layer can absorb oxygen from the second resistive switching layer and undergo an oxidation reaction, thus oxidizing the third resistive switching layer from Ta to unsaturated tantalum oxide.

[0053] Further, the first resistive switching layer includes a first metal oxide, which can be understood as an oxide of a first metal. The second resistive switching layer may include a second metal, a second metal oxide, or a mixture of both, wherein the second metal oxide can be understood as an oxide of a second metal. The third resistive switching layer includes a third metal, a third metal oxide, or a mixture of both, wherein the third metal oxide can be understood as an oxide of a third metal.

[0054] In some embodiments, the second resistive switching layer may be formed directly using a second metal oxide material, such that the second resistive switching layer contains a second metal oxide.

[0055] In other embodiments, a second metal can be used as the material to fabricate the second resistive switching layer. During or after fabrication, the second metal undergoes a redox reaction with the first resistive switching layer to form a second metal oxide, thus containing the second metal oxide in the second resistive switching layer. For example, if metal Hf is used to fabricate the second resistive switching layer, after fabrication, when the device performs electrical operations such as forming, the electrical operation accelerates the oxidation reaction between the metal Hf in the second resistive switching layer and the first resistive switching layer to form hafnium oxide. As another example, if metal Hf is used to fabricate the second resistive switching layer, during or after fabrication, the metal Hf undergoes a redox reaction with the first resistive switching layer under natural conditions, thereby forming hafnium oxide in the second resistive switching layer.

[0056] It should be noted that the first metal, the second metal, and the third metal can be the same metal or different metals. When the three are different metals, the first metal, the second metal, and the third metal can each be a different metal, or some of the first metal, the second metal, and the third metal can be different metals and some can be the same metal. For example, the first metal and the second metal are the same metal, while the second metal and the third metal are different metals.

[0057] It should be noted that the selected first metal has lower metallic reactivity than the selected third metal, in order to ensure that the third resistive switching layer has stronger reducing properties than the first resistive switching layer, and is therefore more easily oxidized.

[0058] Furthermore, in order to ensure that the third resistive switching layer has sufficient reducing power to guarantee that it can obtain oxygen from the first and second resistive switching layers, the standard reduction potential of the third metal and / or the third metal oxide is less than or equal to -0.8V.

[0059] The above embodiments describe a non-volatile two-terminal memory cell with a composite resistive switching layer comprising three structural layers. It is understood that the composite resistive switching layer of the non-volatile two-terminal memory cell provided in this disclosure embodiment may contain a greater number of structural layers. Figure 2 shows an exemplary structural diagram of a non-volatile two-terminal memory cell according to some embodiments of this disclosure. The structure of a non-volatile two-terminal memory cell with a composite resistive switching layer comprising a greater number of structural layers is shown in Figure 2.

[0060] As an example, the first resistive switching layer 21 includes: multiple first sub-resistive switching layers 211 disposed along a first direction, wherein the number of oxygen atoms in each first sub-resistive switching layer 211 decreases layer by layer along the first direction, such that the variation trend of the standard reduction potential of the multiple first sub-resistive switching layers is consistent with the variation trend of the composite resistive switching layer, that is, the standard reduction potential of the multiple first sub-resistive switching layers decreases layer by layer in the first direction.

[0061] It should be noted that in some embodiments, the aforementioned multilayer first sub-resistive switching layer is prepared layer by layer during the preparation of non-volatile end-to-end memory cells. In other embodiments, the aforementioned multilayer first sub-resistive switching layer is formed by the localization of different degrees of redox reactions of the first resistive switching layer under natural conditions after the preparation of a first resistive switching layer.

[0062] As another example, the third resistive switching layer 23 may also include: multiple third sub-resistive switching layers 231 disposed along the first direction, wherein the number of oxygen atoms in each third sub-resistive switching layer 231 decreases layer by layer along the first direction, such that the change trend of the standard reduction potential of the multiple third sub-resistive switching layers is consistent with the change trend of the composite resistive switching layer, that is, the standard reduction potential of the multiple third sub-resistive switching layers decreases layer by layer in the first direction.

[0063] Similar to the multilayer first sub-resistive switching layer, the multilayer third sub-resistive switching layer can be prepared layer by layer, or it can be a layered structure formed by a redox reaction of a third sub-resistive switching layer under natural conditions.

[0064] It should be noted that a non-volatile two-terminal memory cell can include multiple first sub-resistive switching layers and multiple third sub-resistive switching layers simultaneously, or it can include only one of the two types of multiple sub-resistive switching layers mentioned above. No further restrictions are imposed here.

[0065] Furthermore, in a non-volatile end-to-end memory cell containing multiple layers of third sub-resistive switching layers, the uppermost third sub-resistive switching layer, i.e. the third sub-resistive switching layer in contact with the upper electrode, can be made of a third metal to achieve maximum oxidation or oxygen absorption capacity.

[0066] The following provides an exemplary description of the specific materials that can be used in the composite resistive switching layer. As an example, the first metal includes one or more of the following metals: hafnium, titanium, tantalum; the second metal includes one or more of the following metals: hafnium, titanium, tantalum; and / or, the third metal includes one or more of the following metals: hafnium, tantalum, titanium, aluminum.

[0067] Furthermore, in order to ensure that the third resistive switching layer has stronger reducing properties than the first resistive switching layer and is therefore more easily oxidized, the selected first metal has lower metal activity than the selected third metal.

[0068] Some embodiments disclosed herein provide a material selection method that determines the material of the second resistive switching layer based on the materials of the first and third resistive switching layers. Specifically, the second resistive switching layer may use the same metal element as the first resistive switching layer, or the second resistive switching layer may use the same metal element as the third resistive switching layer.

[0069] Assume the first metal is M1, the first metal oxide is M1Ox, M1∈{Hf, Ti, Ta}, the third metal is M3, the third metal oxide is M3Or, M3∈{Hf, Ta, Ti, Al}, then the second metal can be the same as the first metal or the same as the third metal, that is, the second metal is M1 or M3.

[0070] When the second metal and the first metal are both M1, the second metal oxide is M1Oy, where the value of y is less than x, to ensure that the second resistive switching layer is more easily oxidized than the first resistive switching layer. In other words, the second resistive switching layer can use the same metal oxide as the first resistive switching layer, the difference being that the unsaturation degree of the metal oxide in the second resistive switching layer is higher than that in the first resistive switching layer, thereby ensuring that the second resistive switching layer has a lower standard reduction potential and guarantees that the second resistive switching layer has the ability to absorb oxygen from the first resistive switching layer.

[0071] When both the second and third metals are M3, the second metal oxide is M3Oz, where z is greater than r, to ensure that the third resistive switching layer is more easily oxidized than the second. In other words, the second and third resistive switching layers can use the same metal oxide, but the unsaturation degree of the metal oxide in the third resistive switching layer is higher than that in the second resistive switching layer. This ensures that the third resistive switching layer has a lower standard reduction potential, guaranteeing its ability to absorb oxygen from the second resistive switching layer.

[0072] To facilitate understanding, the following example, where M1 is Hf, will be used to illustrate the stoichiometry of oxygen atoms in the first metal oxide M1Ox and the second metal oxide M1Oy.

[0073] Assuming M1 is Hf, the first metal oxide is HfOx, and the second metal oxide is HfOy, the chemical formula for saturated hafnium oxide is HfO2. Since the first resistive switching layer provides oxygen atoms, the first metal oxide can be either saturated or unsaturated. Therefore, the upper limit of the value of x in M1Ox can be 2.0. As an example, the range of x is (1.0, 2.0). To ensure its ability to absorb oxygen from the first metal oxide, the second metal oxide can only be unsaturated, and the stoichiometry of oxygen atoms in the second metal oxide must be less than that in the first metal oxide. Therefore, y is less than x. As an example, the range of y is [1.0, 2.0].

[0074] Similar to the example above, assuming M3 is Ta, the third metal oxide is TaOr, the second metal oxide is TaOz, and the chemical formula for saturated tantalum oxide is Ta2O5, the second and third metal oxides ensure the ability to absorb oxygen from the first metal oxide, and can only be in an unsaturated state. Therefore, the values ​​of r and z are both less than 2.5. As an example, the value range of z is [1.0, 2.5), and the value of z is greater than r.

[0075] When the first resistive switching layer uses HfO2 and the third resistive switching layer uses Ta and / or TaOr, using HfOy, TaOz, and / or Hf as the second resistive switching layer can form a bilayer interface of HfOy / TaOz / Hf and HfO2. This facilitates the formation of a fixed oxygen diffusion region, resulting in more uniform chemical bonding, reduced randomness in the interface oxygen reduction reaction, and thus control over the oxygen vacancy concentration at the contact interface, suppressing disordered oxygen ion diffusion, and ultimately achieving stable resistive switching behavior. Using HfOy, TaOz, and / or Hf as the second resistive switching layer allows for lattice parameters that match both HfO2 and Ta. Compared to non-volatile two-terminal memory cells without a second resistive switching layer, this can absorb and disperse stress at the contact interface, reducing stress concentration and thus reducing interface defects. Furthermore, HfOy, TaOz, and Hf materials are less prone to adverse reactions with HfO2, Ta, and / or TaOr, ensuring good chemical stability in the non-volatile two-terminal memory cells. Furthermore, HfOy, TaOz, and Hf materials possess thermal expansion coefficients that match those of HfO2 and Ta, which can reduce the generation of stress defects by lowering thermal stress. In terms of electrical properties, HfOy, TaOz, and Hf materials exhibit low resistivity and high dielectric constant.

[0076] The above describes the material selection for the first, second, and third resistive switching layers. Some embodiments disclosed herein also include the design of structural parameters of the second resistive switching layer, such as its thickness.

[0077] The second resistive switching layer can be configured with specific structural parameters depending on the type of material used. In some embodiments, the second resistive switching layer comprises a second metal, in which case the thickness of the second resistive switching layer is less than or equal to 5 nm. In other embodiments, the second resistive switching layer comprises a second metal oxide, in which case the thickness of the second resistive switching layer ranges from [2, 8] nm.

[0078] For a specific metal or metal oxide material, the structural parameters of the second resistive switching layer are as follows: if the second resistive switching layer includes a second metal oxide and the second metal is Hf, then the thickness of the second resistive switching layer is in the range of [3,8] nm; if the second resistive switching layer includes a second metal oxide and the second metal is Ta, then the thickness of the second resistive switching layer is in the range of [2,6] nm; if the second resistive switching layer includes a second metal and the second metal is Hf, then the thickness of the second resistive switching layer is less than or equal to 3 nm.

[0079] Based on the non-volatile two-ended storage cells shown in any of the preceding embodiments, some embodiments of this disclosure provide a storage array that includes the non-volatile two-ended storage cells shown in any of the preceding embodiments.

[0080] Based on the above-described storage array, some embodiments disclosed herein also provide a memory including the storage array.

[0081] Based on the aforementioned memory, some embodiments of this disclosure also provide electronic devices including the memory.

[0082] The structure of the non-volatile two-ended memory cell and other products related to it have been introduced above. The fabrication method of the non-volatile two-ended memory cell shown in the previous embodiment will be described below.

[0083] Figure 3 shows an exemplary flowchart of a method 300 for fabricating a non-volatile two-terminal storage device according to some embodiments of the present disclosure. As shown in Figure 3, in step S301, a lower electrode is formed.

[0084] In step S302, a composite resistive switching layer is formed on the lower electrode;

[0085] In step S303, an upper electrode is formed on the composite resistive switching layer to obtain a non-volatile two-terminal memory device.

[0086] In step S302 above, the number of layers in the composite resistive switching layer is greater than 2, and the standard reduction potential of each layer of the composite resistive switching layer is less than 0 and decreases layer by layer along the first direction, where the first direction is the direction from the lower electrode to the upper electrode.

[0087] Furthermore, the composite resistive switching layer of the non-volatile end-to-end storage device includes: a first resistive switching layer, a second resistive switching layer, and a third resistive switching layer disposed along a first direction. In this case, step S302 can be performed as follows: forming a first metal oxide on the lower electrode to form a first resistive switching layer; then forming a second metal and / or a second metal oxide on the first resistive switching layer to form a second resistive switching layer; then forming a third metal and / or a third metal oxide on the second resistive switching layer to form a third resistive switching layer and obtain a composite resistive switching layer, wherein the standard reduction potential of the third metal and / or the third metal oxide is less than or equal to -0.8V to ensure that the third resistive switching layer has a sufficiently strong oxygen uptake capacity or reducing property.

[0088] In some embodiments, the structure of the multilayer sub-resistive switching layer shown in FIG2 can be prepared layer by layer, or it can be a layered structure formed by a redox reaction of a single structural layer under natural conditions.

[0089] Taking the preparation process of the third resistive switching layer as an example, Figure 4 shows an exemplary flowchart of a method 400 for preparing the third resistive switching layer according to some embodiments of the present disclosure. As shown in Figure 4, in step S401, a third metal is formed on the second resistive switching layer.

[0090] In step S402, in response to a preset time, part or all of the third metal is converted into a third metal oxide through a redox reaction to form a third resistive switching layer.

[0091] In step S402 above, part or all of the third metal is converted into a third metal oxide through a redox reaction under natural conditions for a preset time. After the above reaction, the third resistive switching layer includes: multiple third sub-resistive switching layers disposed along a first direction, wherein the number of oxygen atoms in each third sub-resistive switching layer decreases layer by layer along the first direction.

[0092] When all of the third metal is converted into a third metal oxide through a redox reaction, each third sub-resistive layer in the third resistive switching layer exhibits an unsaturated state of third metal oxide. When only a portion of the third metal is converted into a third metal oxide through a redox reaction, the third sub-resistive switching layer in contact with the upper electrode exhibits the third metal, while the remaining third sub-resistive switching layers exhibit an unsaturated state of third metal oxide.

[0093] It should be noted that the above method is only an exemplary method for preparing the third resistive switching layer. In practical applications, an unsaturated third metal oxide can also be formed on the second resistive switching layer during step S401, and the third metal oxide can be further oxidized into other unsaturated third metal oxides in step S402.

[0094] It should also be noted that after the non-volatile end-to-end memory cells are fabricated, electrical operations such as forming can accelerate the redox reaction of the third resistive switching layer, thereby causing the morphology of the third metal / third metal oxide in the third resistive switching layer to change again.

[0095] To provide the oxygen atoms required for the redox reaction of the third resistive switching layer, the first resistive switching layer can also undergo a redox reaction under natural conditions to form a layered structure with multiple sub-resistive switching layers. In other words, during the execution of step S402 above, in response to a preset time, a portion of the first resistive switching layer undergoes a redox reaction to form multiple first sub-resistive switching layers arranged along a first direction, wherein the number of oxygen atoms in each first sub-resistive switching layer decreases layer by layer along the first direction.

[0096] Similar to the third and first resistive switching layers described above, the second metal material used in the formation of the second resistive switching layer may also undergo a redox reaction under natural conditions and / or accelerated electrical operation, resulting in the second resistive switching layer ultimately taking the form of a second metal oxide. In other words, if the second resistive switching layer in a non-volatile dual-terminal memory device is a second metal oxide, the non-volatile dual-terminal memory device can be fabricated using either a second metal oxide or a second metal as the raw material.

[0097] Figure 5 shows an exemplary flowchart of a method 500 for fabricating a non-volatile two-terminal storage device according to some embodiments of the present disclosure. As shown in Figure 5, in step S501, a lower electrode is formed.

[0098] In step S502, a first metal oxide is formed on the lower electrode to form a first resistive switching layer;

[0099] In step S503, a second metal is formed on the first resistive switching layer to form a second resistive switching layer;

[0100] In step S504, a third metal and / or a third metal oxide are formed on the second resistive switching layer to form a third resistive switching layer and obtain a composite resistive switching layer.

[0101] In step S505, an upper electrode is formed on the composite resistive switching layer to obtain a non-volatile two-terminal memory device;

[0102] In step S506, in response to a preset duration and / or the execution of an electrical operation by a non-volatile end-to-end storage device, the second metal is oxidized into a second metal oxide.

[0103] The specific execution methods of steps S501 to S505 can be found in the embodiments described above in conjunction with Figure 3, and will not be repeated here.

[0104] In this embodiment, a second metal is used as the raw material for preparing the second resistive switching layer. After the second resistive switching layer is prepared using the second metal, it can undergo a redox reaction with the material in the first resistive switching layer due to the reducing properties of the second metal. In some embodiments, this redox reaction occurs naturally under natural conditions. In other embodiments, the redox reaction can be accelerated by electrical excitation. In still other embodiments, both natural and accelerated reactions occur simultaneously.

[0105] In any of the embodiments described above in conjunction with Figures 3-5, the raw materials for preparing the second resistive switching layer and / or the third resistive switching layer can be determined based on the raw materials selected for preparing the first resistive switching layer.

[0106] As an example, before forming the third metal and / or third metal oxide on the second resistive switching layer, the third metal and / or third metal oxide can be determined based on the first metal oxide. Specifically, the first metal includes one or more of the following metals: hafnium, titanium, tantalum, and the third metal includes one or more of the following metals: hafnium, tantalum, titanium, aluminum, and the first metal has a lower metallic reactivity than the third metal.

[0107] As another example, before depositing the second metal and / or second metal oxide on the first resistive switching layer, the second metal and / or second metal oxide can be determined based on the first metal oxide and the third metal. Specifically, the first metal includes one or more of the following metals: hafnium, titanium, tantalum; the third metal includes one or more of the following metals: hafnium, tantalum, titanium, aluminum, and the first metal has a lower metallic reactivity than the third metal; the second metal includes one or more of the following metals: hafnium, titanium, tantalum. Further, the second metal can be the same metal as the first or third metal. For example, assuming the first metal is M1, M1∈{Hf, Ti, Ta}, and the first metal oxide is M1Ox, the second metal can be M1, and the second metal oxide can be M1Oy, where the value of y is less than x. As another example, if the third metal is M3, M3∈{Hf, Ta, Ti, Al}, and the third metal oxide is M3Or, the second metal can be M3, and the second metal oxide can be M3Oz, where the value of z is greater than r.

[0108] The specific metal materials of M1 and M3, as well as the specific value ranges of x, y, z, and r, can be found in the non-volatile two-terminal storage unit shown in the previous embodiment, and will not be elaborated here.

[0109] In any of the embodiments described above in conjunction with Figures 3-5, the structural parameters of the second resistive switching layer can be designed when it is prepared. In other words, in some embodiments, when forming the second resistive switching layer, a second metal with a thickness of less than or equal to 5 nm can be formed on the first resistive switching layer; or, a second metal oxide with a thickness range of [2,8] nm can be formed on the first resistive switching layer.

[0110] In summary, the embodiments disclosed herein provide a non-volatile two-terminal memory cell having a composite resistive switching layer. The standard reduction potential of each layer in the composite resistive switching layer decreases layer by layer along a first direction, which is the direction from the lower electrode to the upper electrode. This forms a regular distribution region of reduction in the composite resistive switching layer, providing guidance for the generation and movement of oxygen vacancies or oxygen holes. This is beneficial for strengthening the control of the uniformity of oxygen vacancies or oxygen holes distribution, thereby improving the performance and reliability of the non-volatile memory device.

[0111] This disclosure also provides a method for fabricating a non-volatile two-terminal memory cell. The composite resistive switching layer of the non-volatile two-terminal memory cell prepared by this method has a reducible and regular distribution region, which is beneficial to improving the performance and reliability of the non-volatile memory device.

[0112] While numerous embodiments of this disclosure have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and intent of this disclosure. It should be understood that various alternatives to the embodiments of this disclosure described herein may be employed in the practice of this disclosure. The appended claims are intended to define the scope of this disclosure and therefore cover equivalents or alternatives within the scope of these claims.

[0113] The collection and acquisition of various data disclosed herein comply with relevant laws and regulations and are authorized by the data providers. Any organization or individual that needs to obtain external data shall obtain authorization in accordance with the law and ensure data security. It is prohibited to illegally collect, use, process, or transmit unauthorized or unprotected data, or to illegally buy, sell, provide, or disclose unauthorized or unprotected data.

Claims

1. A non-volatile two-ended storage unit, characterized in that, include: The lower electrode (10), the composite resistive switching layer (20), and the upper electrode (30) are arranged in sequence. The composite resistive switching layer (20) has more than 2 layers; and the standard reduction potential of each layer in the composite resistive switching layer (20) is less than 0 and decreases layer by layer along the first direction, which is the direction from the lower electrode (10) to the upper electrode (30).

2. The non-volatile two-terminal storage unit according to claim 1, characterized in that, The composite resistive switching layer (20) includes: a first resistive switching layer (21), a second resistive switching layer (22), and a third resistive switching layer (23) disposed along a first direction; the first resistive switching layer (21) includes a first metal oxide, the second resistive switching layer (22) includes a second metal and / or a second metal oxide, and the third resistive switching layer (23) includes a third metal and / or a third metal oxide, wherein the standard reduction potential of the third metal and / or the third metal oxide is less than or equal to -0.8V.

3. The non-volatile two-terminal storage unit according to claim 2, characterized in that, The second metal oxide is an oxide formed by the redox reaction between the second metal and the first resistive switching layer.

4. The non-volatile two-terminal storage unit according to claim 2, characterized in that, The first resistive switching layer (21) includes: multiple first sub-resistive switching layers (211) disposed along a first direction, wherein the number of oxygen atoms in each first sub-resistive switching layer (211) decreases layer by layer along the first direction; And / or, The third resistive switching layer (23) includes: multiple third sub-resistive switching layers (231) disposed along the first direction, wherein the number of oxygen atoms in each third sub-resistive switching layer (231) decreases layer by layer along the first direction.

5. The non-volatile two-terminal storage unit according to claim 4, characterized in that, In the multilayer third sub-resistive switching layer, the third sub-resistive switching layer in contact with the upper electrode is made of a third metal.

6. The non-volatile two-terminal storage unit according to claim 2, characterized in that, The first metal includes one or more of the following metals: hafnium, titanium, tantalum; The third metal includes one or more of the following metals: hafnium, tantalum, titanium, and aluminum, and the first metal has a lower metallic activity than the third metal; The second metal includes one or more of the following metals: hafnium, titanium, and tantalum.

7. The non-volatile two-terminal storage unit according to claim 6, characterized in that, The first metal is M1, where M1 ∈ {Hf, Ti, Ta}, and the first metal oxide is M1Ox; The third metal is M3, where M3 ∈ {Hf, Ta, Ti, Al}, and the third metal oxide is M3Or; The second metal is M1 or M3, and the second metal oxide is M1Oy or M3Oz, wherein the value of y is less than x, and the value of z is greater than r.

8. The non-volatile two-terminal storage unit according to claim 7, characterized in that, M1 is Hf, and the value range of x is (1.0, 2.0], and the value range of y is [1.0, 2.0); M3 is Ta, and the value of z is in the range [1.0, 2.5].

9. The non-volatile two-terminal storage cell according to any one of claims 2-8, characterized in that, If the second resistive switching layer includes a second metal, then the thickness of the second resistive switching layer is less than or equal to 5 nm; If the second resistive switching layer includes a second metal oxide, then the thickness of the second resistive switching layer is in the range of [2,8] nm.

10. The non-volatile two-terminal storage unit according to claim 9, characterized in that, If the second resistive switching layer includes a second metal oxide and the second metal is Hf, then the thickness range of the second resistive switching layer is [3,8] nm; If the second resistive switching layer includes a second metal oxide and the second metal is Ta, then the thickness range of the second resistive switching layer is [2,6] nm; If the second resistive switching layer includes a second metal and the second metal is Hf, then the thickness of the second resistive switching layer is less than or equal to 3 nm.

11. A storage array, characterized in that, include: The non-volatile two-ended storage unit as described in any one of claims 1-10.

12. A memory, characterized in that, include: The storage array as described in claim 11.

13. An electronic device, characterized in that, include: The memory as described in claim 12.

14. A method for fabricating a non-volatile two-terminal storage device, characterized in that, include: Form the lower electrode; A composite resistive switching layer is formed on the lower electrode; An upper electrode is formed on the composite resistive switching layer to obtain the non-volatile two-terminal memory device; The composite resistive switching layer has more than 2 layers; the standard reduction potential of each layer of the composite resistive switching layer is less than 0 and decreases layer by layer along a first direction, which is the direction from the lower electrode to the upper electrode.

15. The method according to claim 14, characterized in that, The formation of a composite resistive switching layer on the lower electrode includes: A first metal oxide is formed on the lower electrode to form a first resistive switching layer; A second metal and / or a second metal oxide are formed on the first resistive switching layer to form a second resistive switching layer; A third metal and / or a third metal oxide are formed on the second resistive switching layer to form a third resistive switching layer and obtain the composite resistive switching layer. Wherein, the standard reduction potential of the third metal and / or the third metal oxide is less than or equal to -0.8V.

16. The method according to claim 15, characterized in that, Forming a third metal and / or a third metal oxide on the second resistive switching layer to form the third resistive switching layer includes: A third metal is formed on the second resistive switching layer; In response to a preset time period, part or all of the third metal is converted into a third metal oxide through a redox reaction to form a third resistive switching layer; The third resistive switching layer includes: multiple third sub-resistive switching layers disposed along a first direction, wherein the number of oxygen atoms in each third sub-resistive switching layer decreases layer by layer along the first direction.

17. The method according to claim 16, characterized in that, After forming a third metal on the second resistive switching layer, the method further includes: In response to a preset duration, a portion of the first resistive switching layer undergoes a redox reaction to form multiple first sub-resistive switching layers disposed along a first direction, wherein the number of oxygen atoms in each first sub-resistive switching layer decreases layer by layer along the first direction.

18. The method according to claim 15, characterized in that, Forming a second metal and / or a second metal oxide on the first resistive switching layer includes: A second metal with a thickness of less than or equal to 5 nm is formed on the first resistive switching layer; or... A second metal oxide with a thickness ranging from [2,8] nm is formed on the first resistive switching layer.

19. The method according to claim 15 or 18, characterized in that, Forming a second metal and / or a second metal oxide on the first resistive switching layer includes: forming a second metal on the first resistive switching layer to form a second resistive switching layer; After obtaining the non-volatile two-terminal storage device, the method further includes: in response to a preset duration and / or the non-volatile two-terminal storage device performing an electrical operation, the second metal is oxidized into a second metal oxide.

20. The method according to claim 15, characterized in that, Before forming a third metal and / or a third metal oxide on the second resistive switching layer, the method further includes: determining a third metal and / or a third metal oxide based on the first metal oxide; Before depositing a second metal and / or a second metal oxide on the first resistive switching layer, the method further includes: determining the second metal and / or the second metal oxide based on the first metal oxide and the third metal; The first metal includes one or more of the following metals: hafnium, titanium, and tantalum; the third metal includes one or more of the following metals: hafnium, tantalum, titanium, and aluminum, and the first metal has a lower metallic activity than the third metal; the second metal includes one or more of the following metals: hafnium, titanium, and tantalum.

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