Monocrystalline niobium oxide memristor neuron device and preparation method and application thereof

Abstract

The application relates to a single-crystal niobium oxide memristor neuron device and a preparation method and application thereof, and belongs to the technical field of memristors. The single-crystal niobium oxide memristor neuron device is sequentially provided with a substrate, a bottom electrode layer, a resistance change layer and a top electrode layer from bottom to top; the resistance change layer is a single-crystal niobium dioxide layer, and the number ratio of niobium atoms to oxygen atoms in the single-crystal niobium dioxide layer is 15-20:25-30. By optimizing a sputtering process to control the ratio of niobium atoms to oxygen atoms in amorphous NbO x , a single-crystal niobium oxide memristor is successfully prepared after a conduction band filament is formed by applying a voltage. The single-crystal niobium oxide memristor neuron device has excellent threshold switching characteristics and high stability, and provides important support for in-depth research on the phase change mechanism of the niobium oxide memristor and neural network application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of memristor, and particularly relates to a single-crystal niobium oxide memristor neuron device and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of artificial intelligence and Internet of Things technology, the research on brain-like neural morphological devices has made remarkable progress. Among them, the niobium oxide memristor has attracted widespread attention due to its significant advantages in simulating brain function, effectively executing artificial intelligence algorithms and improving computing efficiency. Niobium dioxide (NbO2) as the core functional material of the memristor neuron device is a kind of excellent phase change material. When the temperature exceeds the phase change threshold of about 1100K due to the applied electric field or local Joule heat, NbO2 will undergo Mott phase transition from the high-resistance tetragonal phase to the low-resistance rutile phase, and the transition process is as fast as nanoseconds (ns). With rich ion dynamics characteristics, ultrafast response speed and good thermal stability, the niobium oxide memristor shows broad application prospects in efficient neural network computing.

[0003] At present, the niobium oxide memristor is usually prepared by magnetron sputtering process. The traditional method is mostly based on metal niobium (Nb) target material, and NbO x thin film is formed by introducing oxygen for reaction deposition. Suhas Kumar et al. pointed out in the research in 2020 (Nature, 585, 518-523, 2020) that the ideal stoichiometric range of NbO x is x = 2-2.3, and the Mott phase transition dynamics performance of NbO x is better in this interval. Therefore, in the subsequent research on niobium oxide neuron memristor, the atomic ratio of oxygen to niobium is usually controlled to be greater than 2. However, the NbO x thin film prepared by this process often generates polycrystalline conductive filament structure containing niobium pentoxide (Nb2O5), niobium dioxide (NbO2) and other oxidation states during the forming process. This polycrystalline mixed state easily causes unstable resistance state, large performance fluctuation and other problems of the device, which seriously restricts the consistency and reliability of the device.

[0004] Although the niobium oxide memristor shows broad application prospects, its internal working mechanism has not been fully revealed, and the complex polycrystalline structure further increases the challenge of mechanism research. Therefore, it is urgent to develop a new method for stably preparing high-performance single-phase NbO2 memristor neuron material to reduce the structural complexity, improve the performance stability of the device, and provide a good material basis for in-depth study of the Mott phase transition mechanism, so as to promote the performance regulation and practical application of neural morphological devices. SUMMARY

[0005] A first object of the present application is to provide a single-crystal niobium oxide memristor neuron device to solve the NbO x The thin film contains a plurality of conductive filament structures, resulting in technical problems of unstable memristor configuration and large performance fluctuation.

[0006] A second object of the present application is to provide a preparation method of the single-crystal niobium oxide memristor neuron device.

[0007] A third object of the present application is to provide an application of the single-crystal niobium oxide memristor neuron device.

[0008] To achieve the above objects, the technical scheme adopted by the present application is as follows:

[0009] A single-crystal niobium oxide memristor neuron device, which is sequentially provided from bottom to top with a substrate, a bottom electrode layer, a resistive switching layer, and a top electrode layer; the resistive switching layer is a single-crystal niobium dioxide layer, and the number ratio of niobium atoms to oxygen atoms in the single-crystal niobium dioxide layer is 15-20:25-30.

[0010] Further, the thickness of the resistive switching layer is 20-40 nm.

[0011] Further, the substrate is a silicon substrate, and the silicon substrate has a silicon dioxide layer with a thickness of 80-120 nm thereon.

[0012] Further, the bottom electrode layer comprises a bottom titanium electrode and a bottom platinum electrode, the bottom titanium electrode is located above the silicon dioxide layer, and the bottom platinum electrode is located above the bottom titanium electrode; the thickness of the bottom titanium electrode is 5-10 nm, and the thickness of the bottom platinum electrode is 35-50 nm; the top electrode layer comprises a top titanium electrode and a top platinum electrode, the top titanium electrode is located above the resistive switching layer, and the top platinum electrode is located above the top titanium electrode layer; the thickness of the top titanium electrode is 5-10 nm, and the thickness of the top platinum electrode is 35-50 nm; the electrode size of the bottom titanium electrode, the bottom platinum electrode, the top titanium electrode, and the top platinum electrode is 0.5-8 μm.

[0013] Further, an aluminum oxide dielectric layer is arranged between the bottom electrode layer and the resistive switching layer.

[0014] A preparation method of a single-crystal niobium oxide memristor neuron device, comprising the following steps:

[0015] S1: bottom electrode layer preparation: cleaning the substrate, performing first patterning treatment on the cleaned substrate, then respectively evaporating titanium metal and platinum metal to form a bottom electrode layer, stripping photoresist, and performing second patterning treatment on the bottom electrode;

[0016] S2: target pre-treatment: using the magnetron sputtering process to optimize the composition of the niobium dioxide target in the mixed gas of oxygen and argon; S3: resistive layer preparation: using the optimized niobium dioxide target in S2, depositing amorphous niobium dioxide by magnetron sputtering to obtain a resistive layer on the second patterned bottom electrode layer in a pure argon atmosphere;

[0017] S4: top electrode layer preparation: stripping the photoresist, performing third pattern processing on the resistive layer, and then respectively evaporating titanium metal and platinum metal to obtain a top electrode layer;

[0018] S5: electrical activation: applying a voltage to induce the formation of a single-crystal niobium dioxide conductive channel, thereby obtaining the single-crystal niobium dioxide memristor neuron device.

[0019] Further, the step of cleaning the substrate in S1 is to use acetone and isopropyl alcohol to ultrasonically clean the substrate, and the ultrasonic power is 40-60W.

[0020] Further, the magnetron sputtering process for target pre-treatment in S2 is:

[0021] S1: pre-sputtering for 5-15min under the condition of vacuum degree ≤4×10 -4 Pa, argon flow rate 30-50sccm, cavity target gas pressure 0.3-1.0Pa, and power 40-60W;

[0022] S2: introducing argon 25-30scccm and oxygen 2-5sccm, sputtering for 15-20min under the condition of cavity target gas pressure 0.3-1.0Pa and power 40-60W; stopping the gas, maintaining for 20-30min under the condition of vacuum degree ≤4×10 -4 Pa;

[0023] S3: introducing argon 30-50sccm, sputtering for 10-20min under the condition of cavity target gas pressure 0.3-1.0Pa and power 40-50W.

[0024] Further, the magnetron sputtering deposition process for resistive layer preparation in S3 is: introducing argon 30-50sccm, sputtering for 10-20min under the condition of back vacuum degree ≤4×10 -4 Pa, cavity target gas pressure 0.3-1.0Pa, and power 40-60W.

[0025] The application of a single-crystal niobium dioxide memristor neuron device in artificial neuron or neural network computing.

[0026] The beneficial effects of the application are:

[0027] Different from the traditional direct sputtering of a metal niobium target in an oxygen atmosphere, the amorphous niobium dioxide thin film with the component ratio controlled in the range of 15-20:25-30 of niobium atom to oxygen atom is deposited by pretreating a niobium dioxide target and regulating the magnetron sputtering conditions in a pure argon atmosphere, the stoichiometric ratio effectively avoids the generation of high-oxygen-phase crystals such as Nb2O5, and provides advantages for electrically activated and induced single-crystal conductive channels.

[0028] The amorphous NbO x The single-crystal niobium oxide memristor is successfully prepared by optimizing the sputtering process to control the ratio of niobium atoms to oxygen atoms and forming a conductive filament by applying voltage. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Figure 1 is a schematic diagram of the structure of the single-crystal niobium oxide memristor neuron device in Example 1, wherein a is a photograph of the single-crystal niobium oxide memristor neuron device taken under an optical microscope (top view), and b is a schematic diagram of the cross section of the single-crystal niobium oxide memristor neuron device;

[0030] Figure 2 Figure 2 is an X-ray photoelectron spectroscopy (XPS) spectrum of the single-crystal niobium oxide memristor neuron device in Example 1;

[0031] Figure 3 Figure 3 is a volatile current-voltage cycle characteristic diagram of the single-crystal niobium oxide memristor neuron device in Example 1;

[0032] Figure 4 Figure 4 is a schematic diagram of the location mark of the crystallization region of the single-crystal niobium oxide memristor neuron device in Example 1, wherein a is a position diagram of the channel, b is a schematic diagram of the location mark, and c is a cross-sectional view of the single-crystal niobium oxide memristor neuron device;

[0033] Figure 5 Figure 5 is a transmission electron microscope (TEM) diagram of the single-crystal niobium oxide memristor neuron device in Example 1 before and after the formation of the conductive channel, wherein a is a state diagram before the formation of the conductive channel, and b is a state diagram after the formation of the conductive channel;

[0034] Figure 6 Figure 6 is an atomic image diagram of the crystallization region of the single-crystal niobium oxide memristor neuron device in Example 1 under a double-sphere-difference correction transmission electron microscope, wherein a is an atomic image diagram, and b is an atomic model diagram.

[0035] Figure 1In the middle: 91, silicon substrate; 84, silicon dioxide layer; 72, bottom titanium electrode; 68, bottom platinum electrode; 45, resistive switching layer; 24, top titanium electrode; 12, top platinum electrode. Detailed Implementation

[0036] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0037] The photoresist used is ARP5350.

[0038] Example 1

[0039] The structure of the single-crystal niobium oxide memristor neuron device in Example 1 is as follows: Figure 1 As shown, the single-crystal niobium oxide memristor neuron device is configured from bottom to top as follows: a silicon substrate 91, a bottom electrode layer, a resistive switching layer 45, and a top electrode layer. The surface of the silicon substrate 91 has a 100 nm silicon dioxide layer 84. The bottom electrode layer includes a bottom titanium electrode 72 and a bottom platinum electrode 68, and the top electrode layer includes a top titanium electrode 24 and a top platinum electrode 12. The top platinum electrode and the bottom platinum electrode are used to connect to the positive and negative voltages, respectively. The resistive switching layer is a 35 nm thick single-crystal niobium dioxide layer. The bottom titanium electrode 72 is located above the silicon dioxide layer 84, and the bottom platinum electrode 68 is located above the bottom titanium electrode 72. The top titanium electrode 24 is located above the resistive switching layer 45, and the top platinum electrode 12 is located above the top titanium electrode 24.

[0040] The fabrication method of single-crystal niobium oxide memristor neuron device is as follows:

[0041] S1: Bottom Electrode Layer Fabrication: The silicon substrate was ultrasonically cleaned with acetone for 5 min and then with isopropanol for 5 min to obtain a cleaned silicon substrate. The ultrasonic power was 40W. Photoresist was coated onto the cleaned silicon substrate to a thickness of 1 μm. A first patterning process was performed on the photoresist-coated silicon substrate. Subsequently, 5 nm of titanium was deposited, followed by 35 nm of platinum to obtain a bottom titanium electrode and a bottom platinum electrode, both with a size of 1 μm. After the deposition was completed, the photoresist was stripped and the surface was dried with a nitrogen gun. A second patterning process was then performed by coating with photoresist to a thickness of 1 μm.

[0042] S2: Target pretreatment: Without placing the bottom electrode layer after the second patterning process in S1, perform target pretreatment magnetron sputtering process to remove the oxide layer on the surface of the niobium dioxide target and optimize the composition of the niobium dioxide target.

[0043] Target material pretreatment process:

[0044] 1) At a vacuum degree of 4×10 -4Pa, the chamber target pressure is 0.5 Pa, and the power is 50 W. The surface particles and part of the oxide layer of the niobium dioxide target are removed by pre-sputtering for 10 min.

[0045] 2) The argon gas is 28 scccm and the oxygen gas is 2 sccm. Sputtering is performed for 15 min under the condition that the chamber target pressure is 0.5 Pa and the power is 50 W. The gas is stopped, and the vacuum degree is maintained at 4x10 -4 Pa for 20 min.

[0046] 3) The argon gas is 30 sccm. Sputtering is performed for 15 min under the condition that the chamber target pressure is 0.5 Pa and the power is 50 W.

[0047] S3: Resistive layer preparation: using the optimized niobium dioxide target in S2, amorphous niobium dioxide is deposited on the second patterned bottom electrode layer in S1 by magnetron sputtering in a pure argon gas atmosphere to obtain a resistive layer. The deposition process is not heated. The magnetron sputtering deposition process parameters are: under the condition of a background vacuum of 4x10 -4 Pa, argon gas 30 sccm, chamber target pressure 0.5 Pa, power 50 W, sputtering for 15 min, and the deposited thickness is 35 nm. The XPS data of the niobium element in the amorphous niobium dioxide layer is shown in Figure 2 , wherein the proportions of niobium elements 2 + , 4 + and 5 + are 169:56:93, and the number ratio of niobium atoms to oxygen atoms is less than 2.

[0048] S5: Top electrode layer preparation: stripping the photoresist, blowing dry the surface with a nitrogen gun, coating photoresist on the surface of the resistive layer for third patterned processing, then evaporating 5 nm of titanium and then evaporating 35 nm of platinum to obtain a top titanium electrode and a top platinum electrode. The electrode size of the top titanium electrode and the top platinum electrode is 1 μm.

[0049] S6: Using a semiconductor tester to apply a voltage to induce the formation of a single-crystal niobium dioxide conductive channel and test, obtaining a memristor with good volatile threshold switch characteristics. The single-crystal niobium dioxide conductive channel has nanosecond-level phase transition characteristics of tetragonal and rutile phases.

[0050] S7: Cross-section sample of a single-crystal niobium oxide memristor neuron device is prepared by focused ion beam (FIB).

[0051] The process conditions for preparing a transmission sample by FIB are as follows:

[0052] 1) The cross Mark beam current of electron beam deposition is 200-2000 pA, and the dose is 0.05-0.2 μC / cm 2Dwell Time: 0.025-0.5 μs.

[0053] 2) When ion beam thinning, the cross Mark horizontal line should be observed on both sides and the knife should be stopped at the maximum intersection point of the Mark.

[0054] S8: The single crystal structure is verified by TEM and spherical aberration-corrected electron microscopy, from which Figure 5 and Figure 6 It can be seen that the single crystal niobium oxide resistive switching neuron device has a single structure of the niobium dioxide single crystal channel component, which is conducive to the observation of the Mott volatile phase change process of the single crystal niobium oxide resistive switching neuron device in the later stage, and fills the gap in the mechanism research in this field at present.

[0055] The electrical properties of the single crystal niobium oxide resistive switching neuron device of Example 1 were tested and characterized at room temperature in air using a Keysight B1500 source meter on a probe station, Figure 3 is a typical I-V cycle curve of the resistive switching neuron in Example 1 under a current limit of 1 mA, which shows the threshold switching characteristics of the single crystal niobium oxide resistive switching neuron device. From Figure 3 it can be seen that the single crystal niobium oxide resistive switching neuron device exhibits volatility under a current limit of 1 mA, wherein the turn-on voltage is 1.64 V, the turn-on current is 200 μA, and the cycle stability is good.

[0056] Example 2

[0057] The preparation method of the single crystal niobium oxide resistive switching neuron device of Example 2 is substantially the same as that of Example 1, and the difference between the preparation method of the single crystal niobium oxide resistive switching neuron device of Example 2 and that of Example 1 is that in the preparation of the resistive switching layer in S3 of Example 2, the power of the magnetron sputtering deposition process parameter is: under the conditions of a background vacuum of 4x10 -4 Pa, argon 30 sccm, target pressure in the cavity 0.5 Pa, and power 40 W, sputtering for 15 min, and the thickness of the deposited layer is 20 nm.

[0058] Example 3

[0059] The preparation method of the single crystal niobium oxide resistive switching neuron device of Example 3 is substantially the same as that of Example 1, and the difference between the preparation method of the single crystal niobium oxide resistive switching neuron device of Example 3 and that of Example 1 is that an aluminum oxide dielectric layer is arranged between the bottom electrode layer and the resistive switching layer, and after the deposition of the aluminum oxide dielectric layer, the photoresist is coated for the second patterning treatment for the deposition of the resistive switching layer.

[0060] The preparation method of the aluminum oxide medium layer is as follows: the substrate with the bottom electrode layer is placed into an atomic layer deposition (ALD) device, trimethylaluminum (TMA) is used as a metal precursor, oxygen plasma is used as an oxidant, the reaction temperature is set to 250 DEG C, the flow rate of the carrier gas Ar is 120 sccm, the flow rate of oxygen is 75 sccm, the pulse time of TMA and oxygen plasma injection is 0.2 s and 12 s respectively, an ALD cycle is formed by alternately performing the TMA and oxygen plasma injection with the cleaning time, and the dense and uniform aluminum oxide film is obtained by repeating the execution, so that the leakage current of the single-crystal niobium oxide resistor neuron device is reduced. The thickness of the aluminum oxide film is 5 nm.

Claims

1. A method for fabricating a single-crystal niobium oxide memristor neuron device, characterized in that, The single-crystal niobium oxide memristor neuron device is sequentially provided with a substrate, a bottom electrode layer, a resistance change layer and a top electrode layer from bottom to top; the resistance change layer is a single-crystal niobium dioxide layer, and the number ratio of niobium atoms to oxygen atoms in the single-crystal niobium dioxide layer is 15-20:25-30; The preparation method of the single-crystal niobium oxide memristor neuron device comprises the following steps: S1: bottom electrode layer preparation: cleaning the substrate, performing first pattern processing on the cleaned substrate, then respectively evaporating titanium metal and platinum metal to form a bottom electrode layer, stripping photoresist, and performing second pattern processing on the bottom electrode; S2: target material pretreatment: under the mixed gas of oxygen and argon, the composition of the niobium dioxide target material is optimized by using a magnetron sputtering process; S3: resistance change layer preparation: using the optimized niobium dioxide target material in S2, amorphous niobium dioxide is obtained by magnetron sputtering deposition on the bottom electrode layer after the second pattern processing under a pure argon atmosphere to obtain the resistance change layer; S4: top electrode layer preparation: stripping the photoresist, performing third pattern processing on the resistance change layer, then respectively evaporating titanium metal and platinum metal to obtain a top electrode layer; S5: electrical activation: applying a voltage to induce the formation of a single-crystal niobium dioxide conductive channel, thereby obtaining the single-crystal niobium oxide memristor neuron device; The magnetron sputtering process for target material pretreatment in S2 is as follows: S2-1: pre-sputtering for 5-15 min under the conditions of vacuum degree ≤ 4 × 10 -4 -4 Pa, argon flow rate 30-50 sccm, cavity target gas pressure 0.3-1.0 Pa, power 40-60 W; S2-2: argon gas 25-30 scccm and oxygen gas 2-5 sccm are introduced, and sputtering is performed for 15-20 min under the conditions of a cavity target gas pressure of 0.3-1.0 Pa and a power of 40-60 W; the gas supply is stopped, and the vacuum degree is maintained at ≤4x10 -4 Pa for 20-30 min; S2-3: argon gas is introduced at a flow rate of 30-50 sccm, and sputtering is performed under the conditions of a target gas pressure of 0.3-1.0 Pa and a power of 40-50 W for 10-20 min.

2. The method of claim 1, wherein the single-crystalline niobium oxide memristor neuron device is prepared by the steps of: The thickness of the resistance change layer is 20-40 nm.

3. The method of claim 1, wherein the single-crystalline niobium oxide memristor neuron device is prepared by the steps of: The substrate is a silicon substrate, and the silicon substrate has a silicon dioxide layer with a thickness of 80-120 nm thereon.

4. The method of claim 3, wherein the single-crystalline niobium oxide memristor neuron device is prepared by the steps of: The bottom electrode layer comprises a bottom titanium electrode and a bottom platinum electrode, the bottom titanium electrode is located above the silicon dioxide layer, and the bottom platinum electrode is located above the bottom titanium electrode; the thickness of the bottom titanium electrode is 5-10 nm, and the thickness of the bottom platinum electrode is 35-50 nm; the top electrode layer comprises a top titanium electrode and a top platinum electrode, the top titanium electrode is located above the resistance change layer, and the top platinum electrode is located above the top titanium electrode layer; the thickness of the top titanium electrode is 5-10 nm, and the thickness of the top platinum electrode is 35-50 nm; the electrode size of the bottom titanium electrode, the bottom platinum electrode, the top titanium electrode and the top platinum electrode is 0.5-8 μm.

5. The method of claim 1, wherein the single-crystalline niobium oxide memristor neuron device is prepared by the steps of: An aluminum oxide dielectric layer is arranged between the bottom electrode layer and the resistance change layer.

6. The method of claim 1, wherein the single-crystalline niobium oxide memristor neuron device is prepared by a process comprising: In S1, the step of cleaning the substrate comprises ultrasonic cleaning of the substrate using acetone and isopropyl alcohol respectively, and the ultrasonic power is 40-60 W.

7. The method of claim 1, wherein the single-crystalline niobium oxide memristor neuron device is prepared by a process comprising: The magnetron sputtering deposition process for preparing the resistance change layer in S3 is as follows: 30-50 sccm of argon is introduced, the background vacuum degree is less than or equal to 4×10 -4 -3 Pa, the cavity target gas pressure is 0.3-1.0 Pa, and the power is 40-60 W, and sputtering is performed for 10-20 min.

8. A single crystalline niobium oxide memristor neuron device, comprising: The single-crystal niobium oxide memristor neuron device is prepared by the preparation method of any one of claims 1-7.

9. Use of the single-crystal niobium oxide memristor neuron device according to claim 8 in artificial neuron or neural network calculation.

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