Memristor based on artificially constructed conductive filament and preparation method thereof

Abstract

The invention discloses a memristor based on artificially constructed conductive filaments and a preparation method of the memristor. The memristor sequentially comprises a substrate, a bottom electrode, a resistive layer and a top electrode from bottom to top, wherein the resistive layer is of a sandwich structure and comprises a plurality of epitaxial layers, and the oxygen vacancy concentration of the plurality of epitaxial layers is distributed in a mode that the oxygen vacancy concentration increases first and then decreases from bottom to top; and a plurality of artificially constructed conductive filaments are formed on the epitaxial layer in the middle. According to the memristor provided by the invention, a resistive layer structure comprising a plurality of epitaxial layers is designed, and the oxygen vacancy concentrations of the plurality of epitaxial layers are distributed from bottom to top in a first-increasing and second-decreasing manner. According to the structural design, the concentration of the oxygen vacancies is accurately regulated and controlled, so that the generation of an efficient oxygen vacancy conductive filament network is promoted, the activity of the oxygen vacancies is improved, the migration process of the oxygen vacancies in the memristor is accelerated, and the memory ability and the nonlinear characteristic of the memristor are remarkably enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductors, and in particular relates to a memristor based on artificially constructed conductive filaments and a preparation method thereof. Background Art

[0002] Under the guidance of "Moore's Law", microelectronic devices represented by complementary metal oxide semiconductor (CMOS) devices show a trend of rapid growth in quantity and integration, and the device size is further reduced. However, with the continuous development of science and technology, traditional silicon-based floating gate structure memory is facing many physical limitations. At the same time, chip energy consumption is also growing rapidly, and reducing device size requires more expensive price and time costs. These problems have led to a gradual slowdown in the growth trend of device integration. Resistor RAM (RRAM) is one of the representative technologies that can solve these problems. As a new generation of non-volatile memory, RRAM has attracted widespread attention due to its advantages such as low cost, simple device structure, extremely small unit size, high speed and low power consumption, and compatibility with CMOS process. It is considered to be the most suitable non-volatile memory for 3D integration. In traditional electronic computers, the von Neumann architecture creates a bottleneck of the so-called separation of computing modules and storage units. This bottleneck causes the central processing unit to read data from the storage unit and then execute the data in the form of commands, with long delay time and high power consumption. Previous studies have found that the computer structure that imitates the human brain, namely neuromorphic computers, is the only way to solve this bottleneck. Due to the fusion of computing modules and storage units, the neural network in the human brain can effectively handle complex tasks. Therefore, in order to imitate and reproduce the structure of the human brain, academic and industrial researchers are actively exploring neuromorphic computers, which require the use of artificial biological synaptic devices for information processing and storage. Memristors are nonlinear resistors with memory functions, so they are also used to realize artificial synapses. Memristors have significant data processing capabilities that are superior to the current von Neumann architecture, so memristors can better simulate and calculate at the biological scale.

[0003] like Figure 1As shown, the traditional gallium oxide memristor mainly adopts a sandwich structure, which is composed of three basic parts, namely two electrodes and a dynamic resistance change layer located between the two, also called a resistance change layer. The core of this resistance change layer is that it contains abundant oxygen vacancies inside, which are responsible for controlling the memristive effect (switching between High Resistance State and Low Resistance State). This switching process essentially involves the local migration of oxygen vacancies in the film and the change of stable state. In the conventional sandwich design, by increasing the oxygen vacancies in the resistance change layer, the nonlinear response of the impedance can be enhanced, especially by suppressing the effective recombination of photogenerated carriers (such as electron-hole pairs), thereby enhancing the so-called "permanent conductance" (PPC) phenomenon.

[0004] However, this traditional architecture has certain limitations. Although increasing the oxygen vacancy concentration can bring about performance improvements, the improvement effect is limited by the single structure of the resistive layer, which affects the stability of the memristive effect. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a memristor based on artificially constructed conductive filaments and a preparation method thereof. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] In the first aspect, the present invention proposes a memristor based on artificially constructed conductive filaments, which comprises a substrate, a bottom electrode, a resistive switching layer and a top electrode from bottom to top;

[0007] The resistive switching layer adopts a sandwich structure, including multiple epitaxial layers, and the oxygen vacancy concentration of the multiple epitaxial layers increases first and then decreases from bottom to top; and a number of artificially constructed conductive filaments are formed on the middle epitaxial layer.

[0008] In a second aspect, the present invention proposes a method for preparing a memristor based on artificially constructed conductive filaments, comprising:

[0009] forming a bottom electrode on the substrate;

[0010] forming a first epitaxial layer having a first oxygen vacancy concentration on the bottom electrode;

[0011] forming a second epitaxial layer having a second oxygen vacancy concentration on the first epitaxial layer;

[0012] etching the second epitaxial layer to form artificially structured conductive filaments;

[0013] Forming a third epitaxial layer having a third oxygen vacancy concentration on the second epitaxial layer, thereby forming a complete resistive switching layer;

[0014] A top electrode is formed on the resistive layer, thereby completing the preparation of a memristor based on artificially constructed conductive filaments.

[0015] Beneficial effects of the present invention:

[0016] The memristor based on artificially constructed conductive filaments proposed in the present invention is designed with a resistive switching layer structure including multiple epitaxial layers, the oxygen vacancy concentration of the multiple epitaxial layers increases first and then decreases from bottom to top, and a number of artificially constructed conductive filaments are formed on the middle epitaxial layer. This structural design includes an alternating layout of low oxygen vacancy concentration areas, high oxygen vacancy concentration areas, and a return to low oxygen vacancy concentration. Through the precise control of the oxygen vacancy concentration, the generation of an efficient oxygen vacancy conductive filament network is promoted, which not only improves the activity of oxygen vacancies, but also accelerates their migration process in the memristor, thereby significantly enhancing the memory capacity and nonlinear characteristics of the memristor; breaking through the bottleneck of improving the performance of the traditional resistive switching layer structure, and achieving a more stable memristive effect.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of a traditional memristor with a sandwich structure resistive switching layer;

[0019] Figure 2 is a schematic structural diagram of a memristor based on artificially constructed conductive filaments provided by an embodiment of the present invention;

[0020] Figure 3 is a schematic diagram of an artificially constructed conductive filament provided by an embodiment of the present invention;

[0021] Figure 4 is a schematic diagram of the principle of formation and breaking of conductive filaments provided by an embodiment of the present invention;

[0022] Figure 5 It is a flow chart of a method for preparing a memristor based on artificially constructed conductive filaments provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] A first aspect of the present invention provides a memristor based on artificially constructed conductive filaments, which comprises, from bottom to top, a substrate, a bottom electrode, a resistive switching layer, and a top electrode;

[0025] The resistive switching layer adopts a sandwich structure, including multiple epitaxial layers, and the oxygen vacancy concentration of the multiple epitaxial layers increases first and then decreases from bottom to top; and a number of artificially constructed conductive filaments are formed on the middle epitaxial layer.

[0026] As an implementation, see Figure 2 , Figure 2 This is a schematic diagram of the structure of a memristor based on artificially constructed conductive filaments provided by an embodiment of the present invention. The resistive switching layer includes, from bottom to top, a first epitaxial layer, a second epitaxial layer, and a third epitaxial layer; the fixed oxygen vacancy concentration or the highest oxygen vacancy concentration of the first epitaxial layer and the third epitaxial layer is less than the fixed oxygen vacancy concentration or the lowest oxygen vacancy concentration of the second epitaxial layer, and the fixed oxygen vacancy concentration of the first epitaxial layer and the third epitaxial layer is the same, and a plurality of artificially constructed conductive filaments are formed in the second epitaxial layer.

[0027] Preferably, the oxygen vacancy concentration of the first epitaxial layer and the third epitaxial layer may be 20%, and the oxygen vacancy concentration of the second epitaxial layer may be 40%.

[0028] Optionally, in this embodiment, the thickness of the first epitaxial layer is the same as the thickness of the third epitaxial layer; the thickness of the second epitaxial layer is greater than the thickness of the first epitaxial layer.

[0029] For example, the thickness of the first epitaxial layer and the third epitaxial layer may be 30-50 nm, and the thickness of the second epitaxial layer may be 100 nm.

[0030] In this embodiment, by etching the second epitaxial layer, a number of artificially structured conductive filaments can be formed, such as Figure 3 As shown, the conductive filaments formed are equivalent to oxygen vacancy columns, and the spacing between them is 50 to 100 nm.

[0031] See also Figure 4 , Figure 4 This is a schematic diagram of the principle of the formation and breaking of conductive filaments provided by an embodiment of the present invention. The present invention promotes the generation of an efficient oxygen vacancy conductive filament network by precisely controlling the concentration of oxygen vacancies, which not only improves the activity of oxygen vacancies, but also accelerates their migration process in the memristor, thereby significantly enhancing the memory capacity and nonlinear characteristics of the memristor. This breaks through the bottleneck of improving the performance of the traditional resistive layer structure and achieves a more stable memristive effect.

[0032] Furthermore, in this embodiment, the substrate can be a silicon substrate, a sapphire substrate or a diamond substrate; the material of the resistive layer can be gallium oxide, or other hafnium oxide or aluminum oxide, the material of the bottom electrode is a graphene two-dimensional material; the material of the top electrode is any one of Ag, Ti, Pt, Au, W, Al or Cu.

[0033] Among them, gallium oxide (Ga 2 O 3 ) material is an emerging ultra-wide bandgap semiconductor material with the advantages of good thermal stability, large bandgap width, large ultraviolet absorption coefficient, and easy material processing. It is an ideal candidate material for solar-blind ultraviolet detection; at the same time, gallium oxide's high resistance characteristics and oxygen-sensitive conductivity are also considered to be one of the ideal candidate materials for memristors. 2 O 3 Memristors can store solar-blind photodetector signals, and are expected to develop light-sensing image recognition and storage systems based on solar-blind bands. This greatly simplifies the complexity of circuits, effectively improves information processing efficiency, and reduces system power consumption. It is one of the frontier hotspots in application field research.

[0034] Therefore, in this embodiment, gallium oxide material is preferably used as the material of the resistive switching layer.

[0035] It is understandable that the bottom electrode can be made of single-layer graphene, few-layer graphene or multi-layer graphene. The present invention uses graphene as the bottom electrode, which can relieve the stress caused by lattice mismatch between the substrate and the epitaxial layer and ensure the high quality of the gallium oxide crystal.

[0036] The memristor based on artificially constructed conductive filaments proposed in the present invention is designed with a resistive switching layer structure including multiple epitaxial layers, the oxygen vacancy concentration of the multiple epitaxial layers increases first and then decreases from bottom to top, and a number of artificially constructed conductive filaments are formed on the middle epitaxial layer. This structural design includes an alternating layout of low oxygen vacancy concentration areas, high oxygen vacancy concentration areas, and a return to low oxygen vacancy concentration. Through the precise control of the oxygen vacancy concentration, the generation of an efficient oxygen vacancy conductive filament network is promoted, which not only improves the activity of oxygen vacancies, but also accelerates their migration process in the memristor, thereby significantly enhancing the memory capacity and nonlinear characteristics of the memristor; breaking through the bottleneck of improving the performance of the traditional resistive switching layer structure, and achieving a more stable memristive effect.

[0037] In addition, the present invention uses gallium oxide material as the resistive switching layer of the memristor. Due to the material's excellent solar-blind ultraviolet detection properties, it can store solar-blind photoelectric detector signals and develop a light-perceiving image recognition storage system based on the solar-blind band, which greatly simplifies circuit design, improves the speed of information processing and reduces energy consumption, opening up new paths for high-efficiency, low-power application scenarios.

[0038] Based on the same inventive concept, the second aspect of the present invention also provides a method for preparing a memristor based on artificially constructed conductive filaments. Figure 5 , Figure 5 1 is a flow chart of a method for preparing a memristor based on artificially constructed conductive filaments provided by an embodiment of the present invention. The method specifically comprises:

[0039] Step 1: Form a bottom electrode on a substrate.

[0040] First, a silicon substrate is prepared.

[0041] Then, a graphene bottom electrode material prepared by a CVD (Chemical Vapor Deposition) process on the copper foil is transferred to the substrate by a wet transfer method to serve as a bottom electrode.

[0042] The graphene bottom electrode may be single-layer, few-layer or multi-layer graphene.

[0043] Step 2: Forming a first epitaxial layer having a first oxygen vacancy concentration on the bottom electrode.

[0044] Specifically, taking the gallium oxide resistive switching layer as an example, a gallium oxide film with a thickness of 30 to 50 nm and a first oxygen vacancy concentration is grown on the bottom electrode by van der Waals epitaxy as the first epitaxial layer. The oxygen vacancy concentration of the first epitaxial layer can be adjusted to a desired range through process parameters. For example, in this embodiment, the fixed oxygen vacancy concentration of the first epitaxial layer can be set to 20%.

[0045] Optionally, the epitaxial growth process of the first epitaxial layer may be any one of the following processes: sputtering, atomic layer deposition, evaporation, pulsed laser deposition, thermal oxidation or chemical vapor deposition.

[0046] Step 3: Forming a second epitaxial layer having a second oxygen vacancy concentration on the first epitaxial layer.

[0047] Specifically, a 100 nm thick gallium oxide film having a certain oxygen vacancy concentration is epitaxially grown on the first epitaxial layer to serve as the second epitaxial layer.

[0048] Optionally, the epitaxial growth process of the second epitaxial layer may be any one of the following processes: sputtering, atomic layer deposition, evaporation, pulsed laser deposition, thermal oxidation or chemical vapor deposition.

[0049] Step 4: Etching the second epitaxial layer to form artificially structured conductive filaments.

[0050] Specifically, by selectively etching the second epitaxial layer, a number of artificially constructed conductive filaments, namely oxygen vacancy columns, can be obtained, thereby adjusting the oxygen vacancy concentration of the second epitaxial layer to a desired range, such as 40% in this embodiment.

[0051] Step 5: Form a third epitaxial layer having a third oxygen vacancy concentration on the second epitaxial layer, thereby forming a complete resistive switching layer.

[0052] Specifically, a gallium oxide thin film having a third oxygen vacancy concentration and a thickness of 30 to 50 nm is grown on the second epitaxial layer by van der Waals epitaxy to serve as the third epitaxial layer.

[0053] The third oxygen vacancy concentration may be the same as the first oxygen vacancy concentration, which is 20%.

[0054] Thus, a resistive switching layer structure having a three-layer sandwich structure is formed.

[0055] Optionally, the epitaxial growth process of the third epitaxial layer may be any one of the following processes: sputtering, atomic layer deposition, evaporation, pulsed laser deposition, thermal oxidation or chemical vapor deposition.

[0056] It can be understood that, in this embodiment, the preparation processes of the first epitaxial layer, the third epitaxial layer and the second epitaxial layer may be the same or different. When the same process is used, different oxygen vacancy concentrations may be obtained by using different process parameters.

[0057] Step 6: Form a top electrode on the resistive layer, thereby completing the preparation of the memristor based on the artificially constructed conductive filaments.

[0058] Specifically, Ag, Ti, Pt, Au, W, Al or Cu metal is deposited on the resistive layer by electron beam evaporation deposition or shadow mask and magnetron sputtering process to form the top electrode.

[0059] Optionally, as an implementation method, first, a forward photoresist (AZ 6112) is coated on the sandwich structure / single-layer graphene / silicon substrate at a rotation speed of 4000 rpm / min for 60 seconds, and cured at 100° C. for 90 seconds.

[0060] Then, Ti metal was deposited by electron beam evaporation as the top electrode.

[0061] At this point, the preparation of memristors based on artificially constructed conductive filaments has been completed.

[0062] The method for preparing a memristor based on artificially constructed conductive filaments provided in the second aspect of the present invention can be used to prepare a memristor based on artificially constructed conductive filaments provided in the first aspect of the present invention, and therefore has similar beneficial effects as the memristor based on artificially constructed conductive filaments provided in the first aspect. Relevant matters can be found in the partial description of the device embodiments.

[0063] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0064] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0066] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A memristor based on artificially constructed conductive filaments, characterized in that: From bottom to top, it includes a substrate, a bottom electrode, a resistive switching layer and a top electrode; The resistive switching layer adopts a sandwich structure, including multiple epitaxial layers, the oxygen vacancy concentration of the multiple epitaxial layers increases first and then decreases from bottom to top; and a number of artificially constructed conductive filaments are formed on the epitaxial layer in the middle.

2. The memristor based on artificially constructed conductive filaments according to claim 1, characterized in that: The resistive layer includes, from bottom to top, a first epitaxial layer, a second epitaxial layer and a third epitaxial layer; wherein the fixed oxygen vacancy concentrations of the first epitaxial layer and the third epitaxial layer are equal and both are less than the fixed oxygen vacancy concentration of the second epitaxial layer; and a plurality of artificially constructed conductive filaments are formed in the second epitaxial layer.

3. The memristor based on artificially constructed conductive filaments according to claim 1, characterized in that: The oxygen vacancy concentrations of the first epitaxial layer and the third epitaxial layer are 20%, and the oxygen vacancy concentration of the second epitaxial layer is 40%.

4. The memristor based on artificially constructed conductive filaments according to claim 1, characterized in that: The thickness of the first epitaxial layer is the same as the thickness of the third epitaxial layer; the thickness of the second epitaxial layer is greater than the thickness of the first epitaxial layer.

5. The memristor based on artificially constructed conductive filaments according to claim 1, characterized in that: The spacing between the artificially constructed conductive filaments is 50 to 100 nm.

6. The memristor based on artificially constructed conductive filaments according to claim 1, characterized in that: The substrate is a silicon substrate, a sapphire substrate or a diamond substrate; the material of the resistive layer is gallium oxide, hafnium oxide or aluminum oxide; the material of the bottom electrode is a two-dimensional graphene material; the material of the top electrode is any one of Ag, Ti, Pt, Au, W, Al or Cu.

7. A method for preparing a memristor based on artificially constructed conductive filaments, characterized in that: include: forming a bottom electrode on the substrate; forming a first epitaxial layer having a first oxygen vacancy concentration on the bottom electrode; forming a second epitaxial layer having a second oxygen vacancy concentration on the first epitaxial layer; Etching the second epitaxial layer to form a plurality of artificially structured conductive filaments; Forming a third epitaxial layer having a third oxygen vacancy concentration on the second epitaxial layer, thereby forming a complete resistive switching layer; A top electrode is formed on the resistive layer, thereby completing the preparation of a memristor based on artificially constructed conductive filaments.

8. The preparation method according to claim 7, characterized in that: A bottom electrode is formed on the substrate, comprising: The graphene prepared by CVD on the copper foil is transferred to the substrate by a wet transfer method to form a bottom electrode.

9. The preparation method according to claim 7, characterized in that: When manufacturing the first epitaxial layer, the second epitaxial layer and the third epitaxial layer, sputtering, atomic layer deposition, evaporation, pulsed laser deposition, thermal oxidation or chemical vapor deposition process is adopted, and during the manufacturing process, different oxygen vacancy concentrations are achieved by adjusting the process parameters.

10. The preparation method according to claim 7, characterized in that: Forming a top electrode on the resistive layer, comprising: Ag, Ti, Pt, Au, W, Al or Cu metal is deposited on the resistive layer by electron beam evaporation deposition or shadow mask and magnetron sputtering process to form a top electrode.

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