A doped vanadium oxide neuromorphic memristor and its manufacturing method and application

Abstract

The present application relates to a kind of doped vanadium oxide neuromorphic memristor and its manufacturing method and application, belong to neuromorphic computing device preparation field.The present application is directed to the problem that the phase transition temperature of vanadium oxide threshold switch device is about 68 DEG C, propose to improve the phase transition temperature of vanadium oxide by doping chromium ion, iron ion, germanium ion, to enhance its stability and reliability in high temperature or high power environment.The memristor improves the performance of memristor by designing via structure, including substrate, bottom electrode, isolation layer and top electrode arranged from bottom to top, the top electrode and bottom electrode are used to connect positive voltage and negative voltage, the isolation layer is provided with resistance variable layer material, and resistance variable layer is doped vanadium oxide layer.The preparation process of the memristor is simple, has good threshold transition characteristics, improves the phase transition temperature of vanadium oxide, and is suitable for large-scale neuromorphic computing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of neuromorphic computing device preparation, and more particularly relates to a doped vanadium oxide neuromorphic memristor and a manufacturing method and application thereof. BACKGROUND

[0002] Mott phase transition materials have attracted extensive attention in recent years due to their rich internal ion dynamics, ultrafast phase transition speed, and obvious differences in electrical and optical characteristics before and after phase transition. Vanadium dioxide (VO2) is a typical Mott phase transition material, which exhibits a high-resistance insulating state at room temperature. When the ambient temperature is changed by electrical or thermal means and exceeds the phase transition temperature, VO2 will undergo Mott phase transition and turn into a low-resistance metallic state. Based on the characteristics of high stability, long life, ultrafast switching speed, low power consumption and high integrability of VO2, it has great application potential in neuromorphic computing, brain-like computing, complex biological neural behavior simulation and multi-modal perception, and effectively reduces the hardware cost, time and energy consumption in information processing and computing.

[0003] However, the phase transition temperature of VO2 is relatively low, generally around 68℃ (about 341K), while the temperature of an integrated circuit chip during operation usually reaches above 80℃ (353K), which will cause the VO2 device to always be in a metallic state and thus cannot function normally, limiting its application in high-temperature environments. SUMMARY

[0004] To solve the problem of mismatch between the phase transition temperature of VO2 devices and the operating temperature of circuit chips, the present application provides a doped vanadium oxide neuromorphic memristor, which can increase the phase transition temperature of vanadium oxide by doping chromium ions, iron ions or germanium ions, so that the device can work normally under high-temperature conditions of a circuit chip, and thus improve its application performance in neuromorphic computing systems. Specifically, by doping chromium ions, iron ions or germanium ions, the structure and phase transition characteristics of the vanadium oxide thin film are optimized, so that the memristor is suitable for a wider range of operating temperatures and neuromorphic computing applications.

[0005] According to a first aspect of the present application, a doped vanadium oxide neuromorphic memristor is provided, comprising a substrate, a bottom electrode, an isolation layer and a top electrode arranged in sequence from bottom to top; a through hole is provided in the isolation layer, and a resistive switching layer material is deposited in the through hole, the resistive switching layer material being vanadium oxide doped with chromium ions, iron ions or germanium ions.

[0006] Preferably, the cross-sectional diameter of the through hole is not greater than 4 um.

[0007] Preferably, the resistance change layer material is sputtered in the via by a radio frequency magnetron sputtering method, and an alloy target is used in the radio frequency magnetron sputtering, the alloy target is a vanadium-chromium alloy, a vanadium-iron alloy or a vanadium-germanium alloy, and the mass percentage of vanadium atoms in the alloy target is 85%-95%.

[0008] Preferably, the resistance change layer material has a thickness of 50 nm-80 nm.

[0009] Preferably, the isolation layer is a plasma-enhanced chemical vapor deposition silicon dioxide layer, and has a thickness of 80 nm-100 nm.

[0010] According to another aspect of the present application, a preparation method of the doped vanadium oxide neuromorphic memristor is provided, and the method comprises the following steps:

[0011] (1) depositing a bottom electrode on a substrate, and then depositing an isolation layer;

[0012] (2) spin-coating a photoresist on the isolation layer obtained in step (1) to form a photoresist film layer, then performing photoetching by introducing a via cross-sectional pattern into a maskless photoetching machine, and then developing to obtain a photoresist mask layer; performing etching by a reactive coupled plasma process to obtain a via;

[0013] (3) spin-coating a photoresist on the structure surface obtained in step (2) to form a photoresist film layer, then performing photoetching by introducing a top electrode pattern into a maskless photoetching machine, and then developing; then performing radio frequency magnetron sputtering on an alloy target, the alloy target is a vanadium-chromium alloy, a vanadium-iron alloy or a vanadium-germanium alloy, and a mixed gas of argon and oxygen is introduced during the radio frequency magnetron sputtering; and then removing the photoresist;

[0014] (4) spin-coating a photoresist on the structure surface obtained in step (3) to form a photoresist film layer, then performing photoetching by introducing a top electrode pattern into a maskless photoetching machine, and then developing; then depositing a top electrode; and then removing the photoresist to obtain a doped vanadium oxide neuromorphic memristor.

[0015] Preferably, in step (3), the pressure in the mixed environment during the radio frequency magnetron sputtering is 0.5 Pa-1 Pa, the flow rate of argon is 98.5 sccm-99.5 sccm, the flow rate of oxygen is 0.5 sccm-1.5 sccm, the radio frequency magnetron sputtering power is 80-120 W, and the background pressure during sputtering is less than 7×10 -4 Pa.

[0016] Preferably, in step (1), a silicon dioxide layer is deposited by a plasma-enhanced chemical vapor deposition process, and the silicon dioxide layer is used as the isolation layer.

[0017] Preferably, the bottom electrode and the top electrode are deposited by a direct current magnetron sputtering method.

[0018] According to another aspect of the present application, there is provided a doped vanadium oxide neuromorphic memristor for use in artificial neurons.

[0019] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages:

[0020] (1) The present application improves the phase transition temperature of vanadium oxide by doping chromium ions, iron ions and germanium ions in vanadium oxide. Since Cr 3+ is the most stable valence state of Cr 3+ , and Cr 3+ has the same rutile structure as V 3+ , the introduction of Cr 3+ can effectively increase the proportion of trivalent vanadium in vanadium oxide, promote the formation of structures with Mott characteristics in local areas, and enhance the lattice stability of the material; the introduction of iron ions changes the electronic state density distribution in vanadium oxide, causing lattice distortion and enhancing the rigidity of the crystal, thereby increasing the phase transition temperature; the introduction of germanium ions enhances the stability of monoclinic V-V dimers in vanadium oxide, thereby inhibiting the transition from low-temperature monoclinic phase to high-temperature rutile phase; the above doping can increase the phase transition temperature of the material, so that the phase transition temperature of vanadium oxide can be increased to more than 380K, thereby greatly expanding its application range in high-temperature environments and solving the challenges faced by current vanadium oxide materials in integrated circuit applications.

[0021] (2) The present application optimizes the overall design and functional layout of the device by providing a through-hole structure. The introduction of the through-hole structure not only improves the current channel performance of the device, but also enhances the thermal stability and electrical performance of the material. This structural optimization can effectively reduce heat accumulation and current loss inside the device, improve the reliability and stability of the device in high-temperature environments, and thus improve the working efficiency of the device. At the same time, by introducing chromium ions, iron ions or germanium ions, the phase transition temperature of vanadium dioxide is increased. After doping chromium ions, iron ions or germanium ions, the lattice structure and electronic properties of vanadium oxide are optimized, thereby increasing its phase transition temperature to more than 380K. The increased phase transition temperature enables vanadium oxide devices to work stably in high-temperature environments, avoiding the phase transition of vanadium dioxide to a metallic state at around 68℃, thereby expanding its application range in practical applications, especially in neuromorphic computing and brain-like computing in high-temperature and high-power working environments. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Figure 1 is a schematic diagram of the vertical structure of the doped vanadium oxide neuromorphic memristor of the present application.

[0023] Figure 2The current-voltage characteristic diagram of the vanadium dioxide-based neuromorphic memristor, which is a comparative example of the present invention, is shown in the range of 30℃-110℃.

[0024] Figure 3 The XPS spectrum of the resistive switching layer of the device is shown in the comparative example of this invention.

[0025] Figure 4 This is a diagram showing the volatile current-voltage cycling characteristics of the neuromorphic memristor doped with vanadium oxide according to Embodiment 1 of the present invention.

[0026] Figure 5 The diagram shows the current-voltage characteristics of the doped vanadium oxide neuromorphic memristor of Embodiment 2 of the present invention at 30°C-110°C.

[0027] Figure 6 This is the XPS spectrum of the doped resistive switching layer of the device in Embodiment 2 of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] To achieve the above objectives, in a first aspect, the present invention provides a neuromorphic memristor based on transition metal-doped vanadium oxide, such as... Figure 1 As shown, it has a through-hole structure, including a substrate 5, a bottom electrode 4, an isolation layer 3 and a top electrode 2 arranged sequentially from bottom to top. The bottom electrode 4 and the top electrode 2 are both prepared by DC magnetron sputtering deposition technology and are used to connect negative voltage and positive voltage, respectively. The isolation layer 3 is a silicon dioxide layer used to isolate the bottom electrode 4 and the top electrode 2. It has through holes and resistive switching material 1 is disposed in the through holes. The substrate 5 is a silicon / silicon dioxide substrate.

[0030] The resistive switching layer material 1 is a doped vanadium oxide material, which is the core functional area of ​​the device. The doped metal ions can be chromium ions, iron ions, or germanium ions. The resistive switching layer is prepared by radio frequency magnetron sputtering deposition technology. The preferred atomic ratio of the alloy target material used in the radio frequency magnetron sputtering deposition is vanadium atoms:metal atoms = (85-95):(15-5). If the metal atom ratio is too high, it will introduce additional phases, which may destroy the original structure of vanadium oxide and result in an insignificant Mott phase transition characteristic of vanadium oxide. If the metal atom ratio is too low, the phase transition temperature of vanadium oxide will not increase significantly. The thickness of the resistive switching layer is preferably 50-80 nm.

[0031] The resistance-switching layer material 1 is a chromium ion-doped vanadium oxide material deposited in the via; the bottom electrode 4 is a titanium / platinum layer with a thickness of 10 / 100 nm deposited on the substrate 5; and the top electrode is a platinum layer with a thickness of 100-150 nm deposited on the isolation layer 3 by a photoresist mask.

[0032] The top electrode 2 and the bottom electrode 4 are used to connect positive and negative voltages, respectively.

[0033] The application also provides a preparation method of a neuromorphic memristor based on a transition metal-doped vanadium oxide, which specifically comprises the following steps:

[0034] Step 1: substrate cleaning: the substrate is subjected to cleaning treatment, and is subjected to ultrasonic cleaning with acetone, ultrasonic cleaning with ethanol and ultrapure water one by one, each for 10-20 minutes, and is blown dry with a nitrogen gun.

[0035] Step 2: bottom electrode deposition: the substrate is placed into a magnetron sputtering cavity, the cavity is pumped to a vacuum state, titanium and platinum are selected as sputtering sources, and a bottom electrode is obtained by direct-current magnetron sputtering deposition.

[0036] In an alternative embodiment, a titanium layer is first deposited, the direct-current magnetron sputtering instrument power is set to 60 W, the argon flow rate is 25 sccm, no heating is performed, and the sputtering duration is set to 3 min 20 s; then a platinum layer is deposited, the direct-current magnetron sputtering instrument power is set to 35 W, the argon flow rate is 25 sccm, no heating is performed, and the sputtering duration is 23 min 40 s.

[0037] Step 3: isolation layer deposition: silicon dioxide is deposited on the bottom electrode obtained in step 2 by plasma-enhanced chemical vapor deposition (PECVD);

[0038] In an alternative embodiment, the deposition temperature is 300℃, and the deposition time is 1 min 53 s.

[0039] Step 4: via preparation: photoresist is spin-coated on the silicon dioxide layer obtained in step 3, a circular pattern is introduced by a maskless photolithography machine, a photoresist mask layer is obtained after development, and then silicon dioxide is etched by inductively coupled plasma etching technology to obtain a via.

[0040] In an alternative embodiment, the photoresist is dropped on the silicon dioxide layer, spin-coated by a spin coater for 45 s at a speed of 1500 r / min-4000 r / min, and subjected to maskless photolithography after baking at 97℃ for 2 min; the etching duration is 52 s.

[0041] Step 5: Resistive switching layer preparation: spin-coat photoresist on the wafer obtained in step 4, introduce resistive switching layer pattern by maskless lithography machine, after development, photoresist mask layer is obtained, place the wafer on the substrate and send it into the chamber, place vanadium-chromium alloy target on the radio frequency target site of the magnetron sputtering instrument, vacuumize the chamber, deposit resistive switching layer at room temperature; remove photoresist;

[0042] In an optional embodiment, the atomic ratio of the vanadium-chromium alloy target is vanadium atom: metal atom = (85-95):(15-5), the mixed ambient pressure during sputtering is 0.5 Pa, the gas flow is argon: oxygen = (98.5-99.5) sccm: (1.5-0.5) sccm, the magnetron sputtering power is set to 80-120 W, and the vacuum degree during sputtering is less than 7*10-6Pa. -4 No heating is required. It should be noted that in addition to the vanadium-chromium alloy target, an alloy target of elements such as germanium, iron, and cobalt can also be selected.

[0043] Step 6: Top electrode deposition: place the wafer obtained in step 5 into the magnetron sputtering chamber, vacuumize the chamber, select platinum as the sputtering source, and deposit the top electrode by direct current magnetron sputtering, then remove the photoresist to obtain a chromium-doped vanadium oxide memristor with volatile resistive switching characteristics.

[0044] In an optional embodiment, the platinum layer is deposited, the direct current magnetron sputtering instrument power is set to 35 W, the argon flow is 25 sccm, no heating is required, and the sputtering time is 23 min 40 s.

[0045] In an optional embodiment, the substrate is a silicon / silicon dioxide substrate, the bottom electrode is a titanium / platinum layer deposited by magnetron sputtering, and the top electrode is a platinum layer deposited by magnetron sputtering, the bottom electrode thickness is 5 / 20-10 / 100 nm, and the top electrode thickness is 100-150 nm.

[0046] To further illustrate the effect of transition metal doping on increasing the phase transition temperature of vanadium oxide, the specific embodiments are described in detail as follows:

[0047] Comparative Example

[0048] In the comparative example, a neural morphological memristor of vanadium oxide without doping transition metal is prepared, the resistive switching layer material is a V2O3 target (purity 99.9%) deposited by direct current magnetron sputtering, the magnetron sputtering power is 200 W, and the gas flow is argon: oxygen = 49.15 sccm: 0.85 sccm.

[0049] Figure 2The I-V curve of the comparative example of the vanadium dioxide-based neuromorphic memristor at a temperature from 30°C to 110°C is shown in the figure. As can be seen from the figure, when the temperature exceeds 70°C, the threshold switching characteristic of the comparative example of the vanadium dioxide memristor disappears, and the device changes to a metal state, so the vanadium dioxide memristor cannot be used at a high temperature. Figure 3 The XPS spectrum of the device resistive switching layer of the comparative example is shown in the figure. As can be seen from the XPS spectrum, in the vanadium dioxide resistive switching layer, vanadium mainly has V 4+ and V 5+ two valence states.

[0050] Example 1

[0051] In the neuromorphic memristor based on transition metal doped vanadium oxide in this example, the resistive switching layer material is a chromium doped vanadium oxide material deposited by a chromium vanadium alloy target with a vanadium atom: metal atom ratio of 95:5 through radio frequency magnetron sputtering, with a thickness of 50 nm. The mixed environment pressure during deposition is 0.5 Pa, the magnetron sputtering power is 120 W, and the background vacuum is 7*e -4 without heating. The bottom electrode is a titanium / platinum layer with a thickness of 100 nm, and the top electrode is a platinum layer with a thickness of 120 nm.

[0052] As Figure 4 shown in the figure, the electrical characteristics of the chromium doped vanadium oxide based memristor in this example are described in detail:

[0053] The electrical characteristics of the memristor were tested and characterized on a probe station using a Keysight B1500 source meter in room temperature air. In the test, the voltage bias was always applied to the top electrode, and the bottom electrode was grounded. Figure 3 The figure is a typical I-V cycle curve of the memristor in this example under a current limit of 1 mA, showing the threshold switching characteristic of the chromium doped vanadium oxide based memristor. As can be seen from the figure, the memristor exhibits a volatile behavior under a current limit of 1 mA, with an opening voltage of 0.22 V, extremely low power consumption, and good cycle performance.

[0054] Example 2

[0055] In the neuromorphic memristor based on transition metal doped vanadium oxide in this example, the resistive switching layer material is a chromium doped vanadium oxide material deposited by a chromium vanadium alloy target with a vanadium atom: metal atom ratio of 95:5 through radio frequency magnetron sputtering, with a thickness of 80 nm. The mixed environment pressure during deposition is 0.5 Pa, the magnetron sputtering power is 120 W, and the background vacuum is 7*e -4 without heating. The bottom electrode is a titanium / platinum layer with a thickness of 100 nm, and the top electrode is a platinum layer with a thickness of 120 nm.

[0056] Figure 5The figure shows the IV curves of the memristor in this embodiment as the temperature increases from 30°C to 110°C. As can be seen from the figure, compared with the undoped vanadium dioxide memristor, the device can operate stably at 110°C. Figure 6 This is the XPS spectrum of the resistive switching layer of the doped device in this embodiment, and... Figure 3 By comparison, V in the resistive switching layer can be observed. 3+ The content of chromium is greatly increased, so the phase transition temperature of vanadium dioxide can be increased by doping with chromium ions. This can solve the problem that vanadium dioxide cannot work normally at temperatures above 68°C, enabling vanadium dioxide devices to work stably in high-temperature environments and expanding its application range in practical applications.

[0057] This invention significantly increases the phase transition temperature of vanadium oxide through doping, enabling the memristor to operate stably over a wider temperature range and solving the problem of the low phase transition temperature of vanadium oxide. Furthermore, the threshold switching characteristics of this memristor are optimized, meeting the application requirements of high-temperature, high-power neuromorphic computing systems.

[0058] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A doped vanadium oxide neuromorphic memristor, characterized in that, The resistive switching layer material is deposited in the through hole in the isolation layer, and the resistive switching layer material is vanadium oxide doped with chromium ions, iron ions or germanium ions. The chromium ions are used to increase the proportion of trivalent vanadium in the vanadium oxide, promote the formation of a structure with Mott characteristics in a local area, and enhance the lattice stability of the material; the iron ions are used to change the electronic state density distribution in the vanadium oxide, cause lattice distortion, enhance the rigidity of the crystal, and thus increase the phase transition temperature; and the germanium ions are used to enhance the stability of monoclinic phase V-V dimer in the vanadium oxide, thereby inhibiting the transition from low-temperature monoclinic phase to high-temperature rutile phase. The phase transition temperature of the doped vanadium oxide neuromorphic memristor is increased to 380K or above. The specific preparation method of the resistive switching layer material deposited in the through hole is as follows: spin coating photoresist on the isolation layer to form a photoresist film layer, then performing photoetching by introducing a through hole cross-sectional pattern into the photoresist film layer through a maskless photoetching machine and developing to obtain a photoresist mask layer; performing etching by a reaction coupled plasma process to obtain a through hole; then performing radio frequency magnetron sputtering on an alloy target at room temperature, the alloy target being a vanadium-chromium alloy, a vanadium-iron alloy or a vanadium-germanium alloy, and a mixed gas of argon and oxygen being introduced during the radio frequency magnetron sputtering process; and then removing the photoresist. During the radio frequency magnetron sputtering process, the pressure in the mixed environment is 0.5 Pa-1 Pa, the flow rate of argon is 98.5 sccm-99.5 sccm, and the flow rate of oxygen is 0.5 sccm-1.5 sccm. The target material used in the radio frequency magnetron sputtering process is an alloy target, the alloy target being a vanadium-chromium alloy, a vanadium-iron alloy or a vanadium-germanium alloy, and the mass percentage of vanadium atoms in the alloy target being 85%-95%.

2. The doped vanadium oxide neuromorphic memristor of claim 1, wherein, The cross-sectional diameter of the through hole is not greater than 4 um.

3. The doped vanadium oxide neuromorphic memristor of claim 1, wherein, The thickness of the resistive switching layer material is 50 nm-80 nm.

4. The doped vanadium oxide neuromorphic memristor of claim 1, wherein, The isolation layer is plasma-enhanced chemical vapor deposition silicon dioxide with a thickness of 80 nm-100 nm.

5. The method of claim 1-4, wherein the method is characterized by, The method comprises the following steps: (1) depositing a bottom electrode on a substrate, and then depositing an isolation layer; (2) spin coating photoresist on the isolation layer obtained in step (1) to form a photoresist film layer, then performing photoetching by introducing a through hole cross-sectional pattern into the photoresist film layer through a maskless photoetching machine and developing to obtain a photoresist mask layer; and performing etching by a reaction coupled plasma process to obtain a through hole; (3) spin coating photoresist on the structure surface obtained in step (2) to form a photoresist film layer, then performing photoetching by introducing a resistive switching layer pattern into the photoresist film layer through a maskless photoetching machine and developing, and then performing radio frequency magnetron sputtering on an alloy target, the alloy target being a vanadium-chromium alloy, a vanadium-iron alloy or a vanadium-germanium alloy, and a mixed gas of argon and oxygen being introduced during the radio frequency magnetron sputtering process; and then removing the photoresist; (4) spin coating photoresist on the structure surface obtained in step (3) to form a photoresist film layer, then performing photoetching by introducing a top electrode pattern into the photoresist film layer through a maskless photoetching machine and developing, and then depositing a top electrode; and then removing the photoresist to obtain the doped vanadium oxide neuromorphic memristor.

6. The method of claim 5, wherein the doped vanadium oxide neuromorphic memristor is prepared by a process comprising: In step (3), the radio frequency magnetron sputtering power is 80 W-120 W, and the sputtering background pressure is less than 7x10 -4 Pa.

7. The method for preparing a neuromorphic memristor of doped vanadium oxide as described in claim 5, characterized in that, In step (1), a silicon dioxide layer is deposited by plasma-enhanced chemical vapor deposition, and the silicon dioxide layer is used as the isolation layer.

8. The method of claim 5, wherein the doped vanadium oxide neuromorphic memristor is prepared by a process comprising: depositing a first layer of a vanadium oxide on a substrate; depositing a second layer of a metal oxide on the first layer of the vanadium oxide; and depositing a third layer of a metal oxide on the second layer of the metal oxide. The bottom electrode and the top electrode are deposited by direct current magnetron sputtering.

9. Use of the doped vanadium oxide neuromorphic memristor according to any one of claims 1-4 in artificial neurons.

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