A threshold switching material, a threshold switching device and a method for manufacturing the same

Abstract

The invention discloses a threshold switch material, a threshold switch device and a preparation method therefor. The chemical formula of the threshold switch material is M x D 1‑x , wherein M is Ag or Cu, D is one of S, Se and Te, and 0<x<0.6. When the amorphous threshold switch material M x D 1‑x is used for a threshold switch device, the device can have a relatively large driving current. Specifically, when a voltage is applied to prompt the device to turn on, the metal element Ag or Cu in the threshold switch material can form a thin conductive filament, which has good electrical conductivity and is beneficial to obtaining a relatively large driving current, and the device is in a low-resistance state at this time. When the device is turned off, the metal element Ag or Cu forming the conductive filament re-diffuses into the threshold switch material due to a large diffusion coefficient, which causes the thin conductive filament to break, and the device restores to a high-resistance state.

Description

Technical Field

[0001] This invention relates to the field of threshold switch technology, and in particular to a threshold switch material, a threshold switch device, and a method for preparing the same. Background Technology

[0002] With the rapid development of the semiconductor industry, phase-change memory (PCM) technology has seen significant advancements, with device structures evolving towards three-dimensional, high-density storage. Intel and Micron jointly developed 3D Xpoint, an advanced three-dimensional memory technology. 3D Xpoint consists of intersecting bit lines and word lines, along with memory storage cells and gating / switching units located between these intersecting points. Compared to traditional 2D memory technologies, it offers higher storage density, lower power consumption, faster lifespan, and faster read / write speeds. The memory storage cells in 3D Xpoint are PCM units, storing information based on the reversible phase transition between crystalline and amorphous states of the phase-change material. The gating / switching units utilize Ovonic Threshold Switching (OTS) devices, made from chalcogenide materials compatible with PCM technology.

[0003] The principle of an OTS device is: to control the switching of the device using an electrical signal, as the applied voltage gradually increases until it reaches a threshold voltage (V). th When the threshold switching device transitions from a high-resistance state (HRS) to a low-resistance state (LRS), the switch opens, and V is generally defined as... th Half of the current value corresponds to the leakage current of the switch (I). off During the voltage maintenance period, the switch remains in the open state, and the current during this period is defined as the drive current (I). on The voltage gradually decreases until it falls below the critical holding voltage (V). hold When the threshold switch returns to its initial high-resistance state, the switch is closed. Therefore, the threshold switch requires a high It. on Low I off Excellent nonlinear switching ratio (I on / I off It also boasts good cycle life and high stability.

[0004] Currently, commercially available threshold switching materials have a high component content and excellent thermal stability, but their switching speed is slow, and they contain toxic elements such as As, making them environmentally unfriendly. Furthermore, multi-component materials are prone to component segregation during repeated operation, affecting device reliability. Therefore, low-component threshold switching materials, especially binary chalcogenide materials, have become a solution. While reported threshold switching devices based on binary chalcogenide systems such as B-Te, C-Te, and Si-Te have high switching speeds, they suffer from low drive current (which is detrimental to achieving a fully high-resistivity state in series memory storage cells, thus affecting the distinction between logic signals "0" and "1") and short cycle life.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a threshold switching material, a threshold switching device and a method for preparing the same, in order to solve the problem of low driving current in existing threshold switching devices based on binary chalcogenide threshold switching materials.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a threshold switching material, wherein the chemical formula of the threshold switching material is M x D 1-x Where M is Ag or Cu, D is one of S, Se, or Te, and 0 <x<0.6。

[0008] A second aspect of the present invention provides a threshold switching device, comprising a bottom electrode, a threshold switching material layer, and a top electrode stacked sequentially from bottom to top, wherein the threshold switching material layer comprises the threshold switching material of the present invention as described above.

[0009] Optionally, the threshold switching material layer includes n+1 core unit layers and n structural stabilizing layers, wherein the n+1 core unit layers and n structural stabilizing layers are alternately stacked, and n is a positive integer greater than or equal to 1; The first core unit layer is attached to the bottom electrode, and the (n+1)th core unit layer is attached to the top electrode. The core unit layer includes the threshold switch material; The structural stabilizing layer comprises a single-crystal TiTe2 grown along the

[001] crystal orientation.

[0010] Optionally, the threshold switching device further includes: A dielectric coating layer covers the side surface of the entire assembly consisting of the bottom electrode, the threshold switch material layer, and the top electrode, which are stacked sequentially.

[0011] Optionally, the threshold switching device further includes: A substrate having a through-hole, wherein the bottom electrode is disposed in the through-hole, and the threshold switch material layer is disposed on the substrate and the bottom electrode; A dielectric coating layer covers the side surface of the entire stacked threshold switch material layer and top electrode.

[0012] Optionally, the material of the bottom electrode includes at least one of W, TiW, TiN, and TiSiN; The material of the top electrode includes at least one of W, TiW, and TiN; The material of the dielectric coating layer includes at least one of SiO2 and Si3N4; The substrate material includes at least one of SiO2 and Si3N4.

[0013] A third aspect of the present invention provides a method for fabricating a threshold switching device, comprising the steps of: Provide bottom electrode; A threshold switching material layer is formed on the bottom electrode, the threshold switching material layer comprising the threshold switching material of the present invention as described above; After forming a top electrode on the threshold switching material layer, the threshold switching device is obtained.

[0014] Optionally, forming a threshold switching material layer on the bottom electrode specifically includes the following steps: n+1 core unit precursor layers and n structural stabilizing layers are alternately formed on the bottom electrode. After annealing, a threshold switching material layer including n+1 core unit layers and n structural stabilizing layers is obtained. n is a positive integer greater than or equal to 1; the first core unit layer is attached to the bottom electrode, and the (n+1)th core unit layer is attached to the top electrode; The core unit precursor layer includes stacked M layer, D layer and M layer, where M is Ag or Cu, and D is one of S, Se and Te; The core unit layer includes the threshold switch material.

[0015] Optionally, the preparation method of the core unit precursor layer includes the following steps: Deposit an M layer with a thickness of 1–5 nm; A D layer with a thickness of 5–15 nm is deposited on the M layer; An M layer with a thickness of 1–5 nm is deposited on the D layer to obtain the core unit precursor layer.

[0016] Optionally, the deposition method includes one of physical vapor deposition and chemical vapor deposition; And / or, the thickness of each structural stabilizing layer is 1–9 nm.

[0017] Beneficial effects: This invention utilizes amorphous threshold switching material M x D 1-x When used in threshold switching devices, this technology enables a larger drive current. Specifically, when a voltage is applied to turn the device on, the metallic elements Ag or Cu in the threshold switching material can form thin conductive filaments with good conductivity, which is beneficial for obtaining a larger drive current; at this time, the device is in a low-resistance state. When the device is turned off, the metallic elements Ag or Cu that formed the conductive filaments, due to their large diffusion coefficient, diffuse back into the threshold switching material, causing the thin conductive filaments to break, and the device returns to a high-resistance state. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the threshold switching device in one embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the threshold switching device before annealing in one embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of the threshold switching device in another embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram of the threshold switching device before annealing in another embodiment of the present invention.

[0022] Figure 5 This is a current-voltage performance curve of the threshold switching device prepared in Embodiment 1 of the present invention.

[0023] Figure 6 The image shows the fatigue cycle performance curve of the threshold switching device prepared in Example 1 of this invention. Detailed Implementation

[0024] This invention provides a threshold switching material, a threshold switching device, and a method for preparing the same. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0026] This invention provides a threshold switching material, wherein the chemical formula of the threshold switching material is M. x D1-x Where M is Ag or Cu, D is one of S, Se, or Te, and 0 <x<0.6。

[0027] In this embodiment, x represents the percentage of atoms of element M in M. x D 1-x The ratio of the total number of atoms, x, to 1-x, is the ratio of the number of atoms of element M to the number of atoms of element D. For example, x = 0.1, 0.2, 0.3, 0.4, or 0.5, etc. Furthermore, the chemical formula of the threshold switch material is M. x D 1-x That is, the threshold switching material is an amorphous alloy material composed of M and D, and the threshold switching material (i.e., the non-static alloy material) is Ag. x S 1-x Ag x Se 1-x Ag x Te 1-x Cu x S 1-x Cu x Se 1-x or Cu x Te 1-x .

[0028] In this embodiment of the invention, an amorphous threshold switching material M x D 1-x When used in threshold switching devices, this allows for a larger drive current. Specifically, when a voltage is applied to turn the device on, the metallic elements Ag or Cu in the threshold switching material can form thin conductive filaments with good conductivity, which is beneficial for obtaining a larger drive current; at this time, the device is in a low-resistance state. When the device is turned off, the metallic elements Ag or Cu that form the conductive filaments, due to their large diffusion coefficient, diffuse back into the threshold switching material, causing the thin conductive filaments to break, and the device returns to a high-resistance state.

[0029] This invention also provides a threshold switching device, wherein, as shown in the embodiments, Figure 1 and 3 As shown, it includes a bottom electrode 120, a threshold switching material layer 130 and a top electrode 140 stacked sequentially from bottom to top. The threshold switching material layer includes the threshold switching material described above in the embodiments of the present invention.

[0030] In this embodiment of the invention, when a voltage is applied to turn the device on, the metallic elements Ag or Cu in the threshold switch material can form thin conductive filaments, which is beneficial for obtaining a larger driving current, and the device is in a low-resistance state at this time. When the device is turned off, the metallic elements Ag or Cu that form the conductive filaments, due to their large diffusion coefficients, re-diffuse into the threshold switch material, causing the thin conductive filaments to break, and the device returns to a high-resistance state. Specifically, before the voltage is applied, M atoms trap holes (M...x D 1-x (A p-type semiconductor containing holes) forms M + When an external voltage is applied, under the influence of an electric field, M + The atoms move from the anode to the cathode and combine with electrons, reducing them to M atoms, which accumulate to form a conductive filament (the filament is thin to facilitate subsequent breakage). The device then exhibits a low-resistance state, achieving the on-state. When the external voltage is less than V... hold When the voltage is maintained, the M element in the formed fine conductive filament will diffuse to the surrounding areas with lower M concentration, causing the conductive filament to break or even disappear. Subsequently, the device exhibits a high resistance state and achieves the off state.

[0031] In some implementations, such as Figure 1 and 3 As shown, the threshold switch material layer 130 includes n+1 core unit layers 131 and n structural stabilization layers 132, which are stacked alternately, and n is a positive integer greater than or equal to 1. The first core unit layer is attached to the bottom electrode, and the (n+1)th core unit layer is attached to the top electrode. The core unit layer includes the threshold switch material; The structural stabilizing layer comprises a single-crystal TiTe2 grown along the

[001] crystal orientation.

[0032] In this embodiment, the structural stabilization layer confines the core unit layer to a two-dimensional scale, suppressing component segregation caused by the large-scale diffusion of M and D, thereby improving the reliability, stability, and fatigue cycle life of the device. The reason for choosing TiTe2 as the material for the structural stabilization layer in this embodiment is that the preparation process of TiTe2 is compatible with the preparation processes of other layer materials; TiTe2 has strong internal chemical bonds and a stable structure, and will not undergo component segregation under high current pulses; TiTe2 grows along the

[001] crystal orientation, so its outermost layer is a layer of Te atoms, followed by a van der Waals-like layer. This configuration is beneficial for improving the ability to suppress the diffusion of elements from adjacent core unit layers.

[0033] In this embodiment, the value of n is not limited; n can be equal to 1, 2, 3, 4, 5, 6, or 7, etc. Figure 1 In the threshold switching device shown, n is 2, such as Figure 3 In the threshold switching device shown, n is 3. In some specific embodiments, n is taken as a positive integer between 2 and 5, which can ensure that the threshold switching material layer has a suitable thickness, so that the threshold switching device has a large drive current.

[0034] In some embodiments, the thickness of the threshold switch material layer is 15-80 nm. Excessive thickness of the threshold switch material layer can reduce the drive current of the threshold switch device, affecting the reversible phase transition of the associated phase-change memory cell. Therefore, the thickness of the threshold switch material layer is no greater than 80 nm. For example, the thickness of the threshold switch material layer can be 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, or 80 nm.

[0035] In some embodiments, the thickness of the structural stabilizing layer is 1–9 nm, for example, it can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, or 9 nm. That is, the thickness of each structural stabilizing layer is 1–9 nm. In some embodiments, the thickness of the core unit layer is 7–25 nm. That is, the thickness of each structural stabilization layer is 7–25 nm. For example, the thickness of the core unit layer is 7 nm, 8 nm, 9 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, or 25 nm, etc.

[0036] In this embodiment of the invention, the threshold switching device includes two structures, one of which is a confinement structure and the other is a T-type structure.

[0037] like Figure 1 As shown, the restricted-structure threshold switching device includes: Bottom electrode 120; A threshold switching material layer 130 is disposed on the bottom electrode 120, and the threshold switching material layer 130 includes the threshold switching material M as described above in the embodiments of the present invention. x D 1-x ; Top electrode 140 is disposed on the threshold switch material layer 130; A dielectric coating layer 150 covers the side surface of the entire structure consisting of the bottom electrode 120, the threshold switching material layer 130, and the top electrode 140. The function of the dielectric coating layer is to prevent oxidation of the threshold switching material.

[0038] In some embodiments, the threshold switching material layer 130 includes n+1 core unit layers 131 and n structural stabilizing layers 132, which are alternately stacked, where n is a positive integer greater than or equal to 1; wherein the first core unit layer is attached to the bottom electrode, and the (n+1)th core unit layer is attached to the top electrode; the core unit layer includes the threshold switching material M. x D 1-xThe structural stabilizing layer comprises a single-crystal TiTe2 grown along the

[001] crystal orientation. Figure 1 In this case, n equals 2.

[0039] In one embodiment, the bottom electrode is cylindrical, and the diameter of the bottom electrode layer is 50–150 nm, for example, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, or 150 nm. The size of the bottom electrode diameter affects the drive current, cycle life, and storage density of the threshold switching device, and the larger the bottom electrode diameter, the worse the overall performance of the threshold switching device. Therefore, when the bottom electrode diameter is 50–150 nm, the overall performance of the threshold switching device is better.

[0040] In the confined structure, the top electrode has the same shape and diameter as the bottom electrode, and there are no specific requirements for the thickness of the bottom and top electrodes. They can be set according to actual needs. For example, the thickness of the bottom electrode and the top electrode can be 20 to 500 nm, such as 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm or 500 nm.

[0041] In one embodiment, the material of the bottom electrode includes at least one of W, TiW, TiN, and TiSiN, but is not limited thereto.

[0042] In one embodiment, the material of the top electrode includes at least one of W, TiW, and TiN, but is not limited thereto.

[0043] In one embodiment, the material of the dielectric coating layer includes at least one of SiO2 and Si3N4, but is not limited thereto.

[0044] like Figure 3 As shown, the T-type threshold switch device includes: Substrate 160 with through holes; Bottom electrode 120 is disposed in the through hole; A threshold switching material layer 130 is disposed on the substrate 160 and the bottom electrode 120. The threshold switching material layer 130 includes the threshold switching material M as described in the embodiments of the present invention. x D 1-x ; Top electrode 140 is disposed on the threshold switch material layer 130; A dielectric coating layer 150 covers the side surface of the entire structure consisting of the threshold switch material layer 130 and the top electrode 140. The function of the dielectric coating layer is to prevent oxidation of the threshold switch material.

[0045] In some embodiments, the threshold switching material layer 130 includes n+1 core unit layers 131 and n structural stabilizing layers 132, which are alternately stacked, where n is a positive integer greater than or equal to 1; wherein the first core unit layer is attached to the bottom electrode, and the (n+1)th core unit layer is attached to the top electrode; the core unit layer includes the threshold switching material M. x D 1-x The structural stabilizing layer comprises single-crystal TiTe2 grown along the

[001] crystal orientation. For example... Figure 3 In this case, n equals 3.

[0046] In some embodiments, the bottom electrode is cylindrical, and its diameter is 50–150 nm, for example, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, or 150 nm. The size of the bottom electrode diameter affects the drive current, cycle life, and storage density of the threshold switching device, and the larger the bottom electrode diameter, the worse the overall performance of the threshold switching device. Therefore, when the bottom electrode diameter is 50–150 nm, the overall performance of the threshold switching device is better.

[0047] In one embodiment, the thickness of the bottom electrode is 100–500 nm, meaning the thickness of the substrate with the via is 100–500 nm, for example, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, or 500 nm. The selection of the bottom electrode thickness primarily considers the substrate covering the bottom electrode (this substrate is an insulating material and prevents oxidation of the bottom electrode). If the substrate thickness is too thin, leakage current will occur, affecting the actual effective utilization efficiency of the device's electrical energy. Therefore, setting the bottom electrode thickness to 100–500 nm (the substrate thickness is also 100–500 nm) ensures that the substrate thickness is not too thin, thus avoiding leakage current.

[0048] In the T-structure, a threshold switching material layer is disposed on the substrate and the bottom electrode, meaning the area of ​​the threshold switching material layer is larger than that of the bottom electrode, and the projection of the threshold switching material layer onto the substrate completely covers the bottom electrode. Furthermore, the projection of the bottom electrode onto the threshold switching material layer is located at the center of the threshold switching material layer.

[0049] Furthermore, the shape of the horizontal cross-section of the threshold switching material layer can be either square or rectangular; in the horizontal direction, the side length of the threshold switching material layer is at least twice the diameter of the bottom electrode. The active region of the threshold switching material layer above the bottom electrode is generally a hemisphere, and this multiple ensures that the active region of the threshold switching material layer completely covers the bottom electrode.

[0050] In one embodiment, the substrate material includes at least one of SiO2 and Si3N4, but is not limited thereto.

[0051] In one embodiment, the material of the bottom electrode includes at least one of W, TiW, TiN, and TiSiN, but is not limited thereto.

[0052] In one embodiment, the material of the top electrode includes at least one of W, TiW, and TiN, but is not limited thereto.

[0053] In one embodiment, the material of the dielectric coating layer includes at least one of SiO2 and Si3N4, but is not limited thereto.

[0054] This invention also provides a method for fabricating a threshold switching device, characterized by comprising the following steps: S1, Provide the bottom electrode; S2. A threshold switch material layer is formed on the bottom electrode, wherein the threshold switch material layer includes the threshold switch material described above in the embodiments of the present invention; S3. After forming the top electrode on the threshold switch material layer, the threshold switch device is obtained.

[0055] In this embodiment, the specific composition, shape, thickness, etc. of the bottom electrode, top electrode, and threshold switch material are as described above and will not be repeated here.

[0056] In step S1, the method for preparing the bottom electrode includes one of physical vapor deposition (including but not limited to sputtering, evaporation, and molecular beam epitaxy) and chemical vapor deposition (including but not limited to plasma-enhanced chemical vapor deposition, atomic layer deposition, atomic vapor deposition, and organometallic compound vapor deposition). Of course, this invention is not limited to these methods; other methods for preparing the bottom electrode are also acceptable. The materials for the bottom electrode are described above and will not be repeated here.

[0057] In step S2, a threshold switching material layer is formed on the bottom electrode using one of the following methods: physical vapor deposition (including but not limited to sputtering, evaporation, molecular beam epitaxy) or chemical vapor deposition (including but not limited to plasma-enhanced chemical vapor deposition, atomic layer deposition, atomic vapor deposition, and organometallic compound vapor deposition).

[0058] In some embodiments, forming a threshold switching material layer on the bottom electrode specifically includes the following steps: n+1 core unit precursor layers and n structural stabilizing layers are alternately formed on the bottom electrode. After annealing, a threshold switching material layer comprising n+1 core unit layers and n structural stabilizing layers is obtained; the thickness of each structural stabilizing layer is 1 to 9 nm. n is a positive integer greater than or equal to 1; the first core unit precursor layer is attached to the bottom electrode, and the (n+1)th core unit precursor layer is attached to the top electrode; the first core unit layer is attached to the bottom electrode, and the (n+1)th core unit layer is attached to the top electrode. The core unit precursor layer includes stacked M layer, D layer and M layer, where M is Ag or Cu, and D is one of S, Se and Te.

[0059] In some implementations, such as Figure 2 and 4 As shown, the preparation method of the core unit precursor layer includes the following steps: M-layer 1311 with a thickness of 1~5nm was deposited; A D layer 1312 with a thickness of 5~15nm is deposited on the M layer; An M layer 1311 with a thickness of 1~5nm is deposited on the D layer to obtain the core unit precursor layer.

[0060] In this embodiment, the core unit precursor layer is a sandwich structure consisting of two M layers with a D layer sandwiched in between. After annealing, all the M elements in the M layers on both sides of the D layer diffuse into the D layer, forming an amorphous alloy M. x D 1-x That is, after annealing, the precursor layer of the core unit is transformed into the core unit layer. This method is used to form the amorphous alloy M. x D 1-x This is because the content of M needs to be controlled very low, and conventional deposition methods such as magnetron sputtering directly prepare M. x D 1-x The M content in the core unit layer is too high. When the device subsequently returns to the off state, a high M content can lead to problems such as incomplete device shutdown and high leakage current. Therefore, the method for preparing the core unit layer provided by this invention can achieve amorphous M with low M content. x D 1-x The preparation of the [material / method] is as follows. Simultaneously, the present invention employs the formation of M layers on both sides of the D layer to ensure uniform diffusion. In this invention, the thickness of the M layer and the D layer can be controlled to regulate the [property / structure]. x D 1-x The content of M and D in the medium. In other words, the magnitude of x can be adjusted by changing the thickness of the M and D layers.

[0061] In this embodiment, as an example, the thickness of each M layer can be 1nm, 2nm, 3nm, 4nm, or 5nm, etc. The thickness of the D layer can be 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, or 15nm, etc.

[0062] In this embodiment, the deposition method includes one of physical vapor deposition (including but not limited to sputtering, evaporation, and molecular beam epitaxy) and chemical vapor deposition (including but not limited to plasma-enhanced chemical vapor deposition, atomic layer deposition, atomic vapor deposition, and organometallic compound vapor deposition). Specifically, the sputtering method is magnetron sputtering, which is relatively flexible. That is, in this embodiment, the above-mentioned deposition methods can be used to deposit the M layer and the D layer.

[0063] In step S3, the preparation method of the top electrode includes, but is not limited to, physical vapor deposition (including but not limited to sputtering, evaporation, molecular beam epitaxy) and chemical vapor deposition (including but not limited to plasma-enhanced chemical vapor deposition, atomic layer deposition, atomic vapor deposition, and organometallic compound vapor deposition).

[0064] The following is an example Figure 4 Taking this as an example, the fabrication method of the threshold switching device is described in detail, specifically including the following steps: S11. Provide a substrate 160 with a through hole, and form a bottom electrode 120 in the through hole; S12. A dielectric coating material layer is deposited on the bottom electrode 120 and the substrate 160. The dielectric coating material layer is etched by an etching process to form a deposition hole in the middle. The bottom of the deposition hole reaches the bottom electrode 120 to obtain a dielectric coating layer 150 with a deposition hole. S13. Deposit M layer 1311 on the bottom electrode 120 and in the deposition holes of the dielectric coating layer 150, deposit D layer 1312 on M layer 1311, and deposit M layer on D layer 1312 to form an active unit precursor layer. A structural stabilizing layer 132 is deposited on the active unit precursor layer, and then the active unit precursor layer and the structural stabilizing layer 132 are deposited alternately to obtain four active unit precursor layers and three structural stabilizing layers (e.g., ...). Figure 4 As shown), and the top layer is the active unit precursor layer; after annealing, the M layer elements in the active unit precursor layer enter the D layer, and the active unit precursor layer is transformed into an active unit layer, resulting in an alternately stacked active unit layer 131 and a structural stabilizing layer 132 (as shown). Figure 3 (as shown) S14. After forming the top electrode 140 on the active unit layer, the threshold switching device is obtained.

[0065] Of course, such as Figure 4 As shown, the top electrode 140 can also be formed on the active unit precursor layer first, and then annealed to transform the active unit precursor layer into the active unit layer.

[0066] The following detailed description uses specific examples.

[0067] Example 1 This embodiment provides a T-type threshold switch device, such as... Figure 3 As shown, the device includes a substrate 160 with a through-hole, wherein a through-hole with a diameter of 90 nm is formed in the substrate 160; a bottom electrode 120 disposed in the through-hole; a threshold switching material layer 130 disposed on the substrate 160 and the bottom electrode 120; and a top electrode 140 disposed on the threshold switching material layer 130; and a dielectric coating layer 150 covering the side of the entire structure formed by the threshold switching material layer 130 and the top electrode 140, wherein the projection of the bottom electrode on the threshold switching material layer is located at the center of the threshold switching material.

[0068] The bottom electrode is made of TiN, is cylindrical, has a diameter of 90 nm, and a thickness of 200 nm; the top electrode is made of W, is cuboid (i.e., a cuboid with a square bottom), has a horizontal cross-section of a square with a side length of 10 μm, and a vertical thickness of 200 nm. The threshold switch material layer 130 is composed of four core unit layers 131 and three structural stabilizing layers 132 stacked alternately. The first core unit layer 131 is attached to the bottom electrode 120, and the fourth core unit layer 131 is attached to the top electrode 140. The material of each core unit layer is Ag. x Te 1-x (x=0.1), with a thickness of 11nm, each structural stabilization layer is made of single-crystal TiTe2 grown along the

[001] crystal direction with a thickness of 1nm; in the horizontal cross section, the shape and size of the threshold switch material layer are the same as the top electrode (it is a square with a bottom side length of 10μm and a cuboid with a thickness of 47nm); The dielectric coating layer is made of SiO2, and its vertical height is equal to the sum of the thickness of the threshold switch material layer and the thickness of the top electrode.

[0069] This embodiment also provides a method for fabricating the above-mentioned T-shaped threshold switch device, including the following steps: (1) Provide a SiO2 substrate with a thickness of 200 nm and a through hole, wherein the diameter of the through hole is 90 nm and the height is 200 nm; (2) A cylindrical TiN layer with a diameter of 90 nm and a thickness of 200 nm is prepared in the through-hole of the substrate by magnetron sputtering to form a bottom electrode; (3) A SiO2 layer is deposited on the surface of the SiO2 substrate by magnetron sputtering. The central part of the SiO2 layer is etched away by etching until the bottom electrode (the central part is a cuboid with a bottom side length of 10 μm and a height of 247 nm) is exposed, forming a deposition hole (i.e., a cuboid with a bottom side length of 10 μm and a height of 247 nm). The remaining part of the SiO2 layer is the dielectric coating layer. (4) The background vacuum of magnetron sputtering is 1×10⁻⁶. -5 At a sputtering pressure of 0.2 Pa, an Ag gas pressure of 6 W was used to sputter the dielectric coating layer on the bottom electrode layer for 1 min, resulting in an Ag layer with a thickness of 1 nm and a bottom side length of 10 μm (a square cross-section in the horizontal direction). Then, a Te layer with a thickness of 9 nm and a bottom side length of 10 μm (a square cross-section in the horizontal direction) was sputtered on the Ag layer for 1 min. Finally, an Ag layer with a thickness of 1 nm and a bottom side length of 10 μm was sputtered on the Te layer for 1 min (i.e., forming the active unit precursor layer). A TiTe2 layer (i.e., a structurally stable layer) with a thickness of 1 nm was obtained by simultaneously sputtering a Ti single-element target (sputtering power of 10 W) and a Te single-element target (sputtering power of 15 W) on the Ag layer for 30 s.

[0070] (5) Repeat step (4) 4 times, alternately sputtering Ag layer, Te layer, Ag layer and TiTe2 layer to obtain 8 Ag layers, 4 Te layers and 3 TiTe2 layers. Then place the device at 300°C for 0.5 h to form a threshold switch material layer, which includes 4 Ag layers. x Te 1-x (x=0.1) layers and 3 TiTe2 layers; (6) A TiN layer with a thickness of 200 nm and a bottom side length of 10 μm is deposited in the deposition holes of the dielectric coating layer on the threshold switch material layer by chemical vapor deposition to form the top electrode and obtain the threshold switch device.

[0071] Testing showed that the current density of the threshold switching material layer in the T-structure threshold switch device of Example 1 was ≥160 MA·cm. -2 High-resistance to low-resistance transition voltage V th It is 2.2V.

[0072] The current-voltage operating performance curve of the T-structure threshold switch device in Example 1 is as follows: Figure 5 As shown, the threshold switching device can achieve a high-resistance state (HRS) to low-resistance state (LRS) turn-on operation at a voltage of 2.2V, and a high-resistance state (HRS) to low-resistance state (LRS) turn-off operation when the voltage drops to 0.7V. Unlike metal tellurides such as TiTe2, which always remain in a low-resistance state and cannot achieve switching operation, this embodiment is based on a 47nm thick Ag... 0.1 Te 0.9 The threshold switching device in the layer can achieve a high-resistance to low-resistance switching operation. Furthermore, by... Figure 5 It can be seen that the drive current of the T-structure threshold switch device in Example 1 is 1×10⁻⁶. -2 A, leakage current is 1×10 -9 A.

[0073] The fatigue cycle performance curve of the T-structure threshold switch device in Example 1 is as follows: Figure 6 As shown, during repeated switching operations 1×10 9 After this, the threshold switching device still did not fail, and the switching ratio was at least 7 orders of magnitude.

[0074] Based on testing, according to existing B 0.3 Te 0.7 The T-type threshold switch device (the only difference from Example 1 is that the threshold switch material is B) 0.3 Te 0.7 The drive current is 1×10 -4 A, leakage current is 1×10 -9 A, cycle life is 1×10 8 Next. Based on existing C 0.35 Te 0.65 The T-structure threshold switch device (the only difference from Example 1 is that the threshold switch material is C) 0.35 Te 0.65 The drive current is 5 × 10 -4 A, leakage current is 5×10 -9 A, cycle life is 1×10 8 Based on existing Si 0.24 Te 0.76 The T-structure threshold switch device (the only difference from Example 1 is that the threshold switch material is Si) 0.24 Te 0.76 The drive current is 8 × 10 -4 A, leakage current is 8×10 -10 A, cycle life is 1×10 5 The above data is summarized in Table 1 below.

[0075] Table 1 Test data for different threshold switching devices

[0076] As can be seen, the T-type threshold switching device provided by the present invention has higher drive current, lower leakage current, longer cycle life and better stability compared with existing threshold switching devices based on binary systems such as B-Te, C-Te and Si-Te.

[0077] Example 2 This embodiment provides a T-type threshold switching device, which differs from Embodiment 1 in that the thickness of the core unit layer is 12nm.

[0078] The fabrication method of the T-structure threshold switch device differs from that of Example 1 only in that: The base vacuum of magnetron sputtering is 1×10⁻⁶. -5 Pa, the Ar gas pressure in the cavity during sputtering is 0.2 Pa. An Ag single-element target (sputtering power of 6 W) is used to sputter in the deposition hole of the dielectric coating layer on the bottom electrode for 2 min to obtain an Ag layer with a thickness of 2 nm and a bottom side length of 10 μm. Then, a Te single-element target (sputtering power of 10 W) is used to sputter on the Ag layer for 1 min to obtain a Te layer with a thickness of 8 nm and a bottom side length of 10 μm (the horizontal cross section is square). Then, an Ag single-element target (sputtering power of 6 W) is used to sputter on the Te layer for 1 min to obtain an Ag layer with a thickness of 2 nm and a bottom side length of 10 μm (the horizontal cross section is square). Then, a Ti single-element target (sputtering power of 10 W) and a Te single-element target (sputtering power of 15 W) are used to sputter on the Ag layer for 30 s to obtain a single crystal TiTe2 with a thickness of 1 nm grown along the

[001] crystal direction.

[0079] Testing revealed that the T-shaped threshold switch device provided in this embodiment has similar threshold transition characteristics to that of Embodiment 1.

[0080] Example 3 This embodiment provides a T-shaped threshold switch device, which differs from Embodiment 1 only in that the core unit layer is made of Cu. x Se 1-x (x=0.1); The fabrication method of the T-structure gating switch device differs from that of Example 1 only in that the base vacuum of the magnetron sputtering method is 1×10⁻⁶. -5Pa, the Ar gas pressure in the cavity during sputtering is 0.2 Pa. A Cu single-element target (sputtering power of 6 W) is used to sputter in the deposition hole of the dielectric coating layer on the bottom electrode for 1 min to obtain a Cu layer with a thickness of 1 nm and a bottom side length of 10 μm. Then, a Se single-element target (sputtering power of 15 W) is used to sputter on the Cu layer for 1 min to obtain a Se layer with a thickness of 9 nm and a bottom side length of 10 μm (the horizontal cross section is square). Then, a Cu single-element target (sputtering power of 6 W) is used to sputter on the Se layer for 1 min to obtain a Cu layer with a thickness of 1 nm and a bottom side length of 10 μm. Then, a Ti single-element target (sputtering power of 10 W) and a Te single-element target (sputtering power of 15 W) are used to sputter on the Cu layer for 30 s to obtain a TiTe2 layer with a thickness of 1 nm.

[0081] Testing revealed that the T-structure threshold switch device provided in this embodiment has similar resistance switching characteristics to that of Embodiment 1.

[0082] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A threshold switching device, characterized in that, It includes a bottom electrode, a threshold switching material layer, and a top electrode, which are stacked sequentially from bottom to top. The threshold switch material layer includes n+1 core unit layers and n structural stabilization layers, which are alternately stacked, where n is a positive integer greater than or equal to 1. The first core unit layer is attached to the bottom electrode, and the (n+1)th core unit layer is attached to the top electrode. The core cell layer comprises a threshold switching material; the chemical formula of the threshold switching material is M x D 1-x x, wherein M is Ag or Cu, D is one of S, Se and Te, and 0<x<0.6; the structure stabilization layer comprises single-crystal TiTe2 grown along the [001] crystal orientation.

2. The threshold switching device according to claim 1, characterized in that, The threshold switching device further includes: A dielectric coating layer covers the side surface of the entire assembly consisting of the bottom electrode, the threshold switch material layer, and the top electrode, which are stacked sequentially.

3. The threshold switching device according to claim 1, characterized in that, The threshold switching device further includes: A substrate having a through-hole, wherein the bottom electrode is disposed in the through-hole, and the threshold switch material layer is disposed on the substrate and the bottom electrode; A dielectric coating layer covers the side surface of the entire stacked threshold switch material layer and top electrode.

4. The threshold switching device according to claim 3, characterized in that, The material of the bottom electrode includes at least one of W, TiW, TiN, and TiSiN; The material of the top electrode includes at least one of W, TiW, and TiN; The material of the dielectric coating layer includes at least one of SiO2 and Si3N4; The substrate material includes at least one of SiO2 and Si3N4.

5. A method for fabricating a threshold switching device, characterized in that, Including the following steps: Provide bottom electrode; A threshold switching material layer is formed on the bottom electrode; After forming a top electrode on the threshold switching material layer, the threshold switching device is obtained; The process of forming a threshold switching material layer on the bottom electrode specifically includes the following steps: n+1 core unit precursor layers and n structural stabilizing layers are alternately formed on the bottom electrode. After annealing, a threshold switching material layer including n+1 core unit layers and n structural stabilizing layers is obtained. n is a positive integer greater than or equal to 1; the first core unit layer is attached to the bottom electrode, and the (n+1)th core unit layer is attached to the top electrode; The core unit precursor layer includes stacked M layer, D layer and M layer, where M is Ag or Cu, and D is one of S, Se and Te; The core unit layer includes a threshold switching material; the chemical formula of the threshold switching material is M. x D 1-x Where M is Ag or Cu, D is one of S, Se, or Te, and 0 <x<0.6。 6. The preparation method according to claim 5, characterized in that, The preparation method of the core unit precursor layer includes the following steps: Deposit an M layer with a thickness of 1–5 nm; A D layer with a thickness of 5–15 nm is deposited on the M layer; An M layer with a thickness of 1–5 nm is deposited on the D layer to obtain the core unit precursor layer.

7. The preparation method according to claim 6, characterized in that, The deposition method includes one of physical vapor deposition and chemical vapor deposition. And / or, the thickness of each structural stabilizing layer is 1–9 nm.

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