Digital memristor based on amorphous yttrium oxide / hafnium oxide double-layer structure and preparation method and application thereof

Abstract

The invention discloses a digital memristor based on an amorphous hafnium oxide / yttrium oxide double-layer structure and a preparation method and application thereof, and belongs to the technical field of nonvolatile resistive random access memories. A first conductive film is deposited on the high-flatness substrate in a physical vapor deposition mode to serve as a bottom conductive electrode; a target material containing yttrium and hafnium elements is adopted, an amorphous yttrium oxide film and an amorphous hafnium oxide film are sequentially deposited on the bottom conductive electrode, and an amorphous yttrium oxide / hafnium oxide double-layer structure is obtained and serves as a functional layer; and continuously depositing a second conductive film on the functional layer by adopting the mask plate to serve as an upper conductive electrode, thereby obtaining the digital memristor based on the amorphous yttrium oxide / hafnium oxide double-layer structure. The structure construction and preparation process is simple, and the material cost is low; meanwhile, by controlling the cut-off voltage and the limiting current, the multi-level storage capacity is shown, the potential advantage of high storage density is achieved while a high storage window is shown, and the good market application prospect is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-volatile memory, and in particular relates to a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure and a preparation method and application thereof. Background Art

[0002] Compared with traditional non-volatile memories such as flash memory, memristors have the advantages of simple structure, low read and write power consumption, high storage density, and compatibility with complementary metal semiconductor processes. They are considered to be the most promising new generation of non-volatile memories. At the same time, with the rapid development of technologies such as big data, the Internet of Things, and artificial intelligence, memristors have shown great application value in realizing storage and computing integration. In addition, memristors are one of the key research directions for creating artificial neuromorphic computing in the future because they can simulate the signal transmission between biological synapses and neurons. Memristors are usually composed of a simple metal / resistive functional layer / metal sandwich structure. Currently, materials such as metal oxides, perovskites, and halides have been found to be able to be used as the resistive functional layer of memristors. In particular, binary transition metal oxides have the advantages of low cost and simple preparation, and are considered to be the most promising resistive functional materials. Materials such as titanium oxide, zinc oxide, zirconium oxide, tungsten oxide, hafnium oxide, and tantalum oxide have attracted the attention of researchers. Among them, amorphous hafnium oxide materials are ideal resistive functional materials because of their wide band gap, high dielectric constant, excellent resistance characteristics, and compatibility with CMOS. However, the stability and switching window performance of memristors built based on hafnium oxide are not ideal, which seriously restricts their application prospects.

[0003] In recent years, valence change memory has been widely recognized as the physical mechanism of oxide-based resistive memory operation, and the resistive behavior is related to the migration of ion defects. For resistive memristors that conform to the physical model of conductive filament formation / fracture, the resistive performance can be effectively regulated by controlling the migration barrier and concentration of oxygen defects that form conductive filaments. Based on this, constructing a memristor by stacking other oxide layers is considered to be one of the effective strategies to change the movement of ions in the resistive layer and thus improve the resistive switching characteristics of the memory. Among them, yttrium oxide has the advantages of wide band gap, low leakage current and good thermal stability. In particular, amorphous yttrium oxide has abundant oxygen defects, making it a good material for improving resistive performance. However, up to now, there has been no report on the preparation method of using yttrium oxide / hafnium oxide double-layer structure to construct a memristor and realize a high storage window digital memristor.

[0004] Therefore, in view of the dilemma that the existing hafnium oxide memristor has to be further improved in terms of stability and switching window, it is urgent to improve the stability and switching window of the memristor from the perspective of device design to realize its application in data storage and other fields. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure and a preparation method and application thereof, so as to solve the technical problem that the existing memristor has a small switching window resulting in a high probability of data storage and reading errors.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure, comprising the following steps: 1) On a highly flat substrate, a first conductive film is deposited by physical vapor deposition as a bottom conductive electrode of a digital memristor; 2) using a target material containing yttrium and a target material containing hafnium, on the bottom conductive electrode prepared in step 1), sequentially depositing an amorphous yttrium oxide film and an amorphous hafnium oxide film by physical vapor deposition to obtain an amorphous yttrium oxide / hafnium oxide double-layer structure as a functional layer of a digital memristor; 3) Using a mask, a second conductive film is deposited on the functional layer prepared in step 2) by physical vapor deposition as an upper conductive electrode of the digital memristor, thereby obtaining a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure.

[0007] Preferably, in step 1), the high-flatness substrate is polished single-crystal silicon grown with silicon dioxide or highly transparent insulating glass.

[0008] Preferably, in step 1), the physical vapor deposition method is any one of thermal evaporation, electron beam evaporation and magnetron sputtering; the first conductive film is any one of ITO, Pt, Au, W and TiN; and the thickness of the bottom conductive electrode is 20-200 nm.

[0009] Preferably, in step 2), the physical vapor deposition method is any one of radio frequency magnetron sputtering, direct current magnetron sputtering, pulsed laser deposition and molecular beam epitaxy; the target material containing yttrium element is a metal target material or a corresponding oxide target material; the target material containing hafnium element is a metal target material or a corresponding oxide target material.

[0010] Preferably, in step 2), the growth power during the deposition of the amorphous yttrium oxide thin film is 20-200 W; the growth time is 0.5-5 min; the substrate heating temperature during the growth process is 100-500°C; a mixed gas of argon and oxygen is introduced during the growth process; the growth gas pressure is 0.1-2 Pa, the argon flow rate is 5-35 sccm; and the oxygen flow rate is 5-35 sccm.

[0011] Preferably, in step 2), the growth power during the deposition of the amorphous hafnium oxide film is 30-350 W; the growth time is 2-20 min; the substrate heating temperature during the growth process is 50-500° C.; a mixed gas of argon and oxygen is introduced during the growth process; the growth gas pressure is 0.1-5 Pa, the argon flow rate is 10-80 sccm, and the oxygen flow rate is 1-20 sccm.

[0012] Preferably, in step 2), the thickness of the amorphous yttrium oxide film is 10-40 nm; the thickness of the amorphous hafnium oxide film is 20-80 nm.

[0013] Preferably, in step 3), the mask is a circular mask, and the diameter of the circular mask is 20-300 μm; the physical vapor deposition method is any one of thermal evaporation, electron beam evaporation and magnetron sputtering; the second conductive film is any one of ITO, Pt, Au, W and TiN; the thickness of the upper conductive electrode is 20-200 nm.

[0014] The present invention also discloses a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure, which is prepared by the above-mentioned preparation method, and comprises, from bottom to top, a bottom conductive electrode, a functional layer and an upper conductive electrode, wherein the functional layer is an amorphous yttrium oxide / hafnium oxide double-layer structure.

[0015] The invention also discloses the application of the digital memristor based on the amorphous yttrium oxide / hafnium oxide double-layer structure prepared by the preparation method in a non-volatile resistive random access memory.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure. A high-flatness substrate is selected to construct the memristor, and the high-flatness substrate is the basis for ensuring the stability and reliability of the electrical properties of the memristor; a high-stability first conductive film of a certain thickness is deposited on the substrate by physical vapor deposition as the bottom conductive electrode of the memristor; the physical vapor deposition method has the advantages of high stability and good repeatability, and the prepared high-stability conductive film has high adhesion to the substrate and the resistive switching functional layer; the high-stability conductive film is used as the bottom conductive electrode of the memristor, which is an important component for obtaining an excellent memristor. A high dielectric constant amorphous yttrium oxide film and a hafnium oxide film are deposited in sequence by physical vapor deposition to obtain an amorphous yttrium oxide / hafnium oxide double-layer structure as the functional layer of a high storage window digital memristor; the high dielectric constant amorphous yttrium oxide film and amorphous hafnium oxide film are deposited by physical vapor deposition, which has good repeatability and the prepared device has the advantage of high stability; the key to achieving a high switching window is to control the morphology of the conductive filaments by growing yttrium oxide and hafnium oxide in sequence from bottom to top; both have the characteristics of wide band gap, high dielectric constant, excellent resistance characteristics and compatibility with CMOS, and are ideal resistive functional materials. A high-stability second conductive film of a certain thickness is continuously deposited on the grown amorphous yttrium oxide / hafnium oxide double-layer structure functional layer as the upper conductive electrode of the digital memristor, to obtain a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure; a high-stability second conductive film of a certain thickness is used as the upper conductive electrode, which is an important component to further ensure the stability of the memristor. Improving the read and write stability and reliability of the memristor by increasing the storage window is an important resistive performance parameter to improve its application prospects. The excellent physical properties of amorphous hafnium oxide materials such as wide band gap, scalability, and high density make it one of the ideal materials for building resistive memory. However, the memristor currently built based on hafnium oxide needs to be further improved in terms of stability and switching window, which seriously restricts its application prospects. The present invention uses a certain thickness of yttrium oxide layer rich in oxygen defects and a hafnium oxide thin film layer to prepare a stack as the resistive functional layer of the memristor, and obtains a digital memristor with excellent resistive performance such as a high storage window. Compared with the memristor with a single hafnium oxide thin film layer, the digital memristor based on the double-layer structure of amorphous yttrium oxide / hafnium oxide constructed in this scheme has broad application prospects in terms of high storage window, high-density storage, etc.

[0017] Furthermore, a high-storage-window memristor is constructed by using a polished single-crystal silicon or highly transparent insulating glass grown with a layer of silicon dioxide with high flatness as a substrate. If the flatness of the substrate is low, the conductive electrodes and functional layers behind it will be uneven, reducing the stability and performance of the device; polished single-crystal silicon or insulating glass grown with silicon dioxide can ensure that the current of the constructed memristor will not pass through the substrate, which can improve the reliability of the memristor performance.

[0018] Furthermore, the bottom conductive electrode and the upper conductive electrode are deposited by physical vapor deposition such as thermal evaporation, electron beam evaporation and magnetron sputtering. The conductive film prepared by the above physical vapor deposition method has high adhesion, high stability and repeatability, and is compatible with the current mainstream CMOS process. One of ITO, Pt, Au, W or TiN is used as the conductive electrode of the device. Compared with metal electrodes with relatively large atomic activity such as Ag and Cu, the electrochemical properties of the above electrodes are inert to a certain extent. The electrode atoms of the memristor constructed in this way will not participate in the resistive switching behavior, ensuring that the device has higher stability. The thickness of the designed bottom conductive electrode and the upper conductive electrode is 20~200 nm. Too thin electrodes cannot ensure the stability of the memristor, and too thick electrodes will lead to poor adhesion between the electrode and the contacting functional layer, while also bringing too high a cost.

[0019] Furthermore, the functional layer is deposited by physical vapor deposition methods such as radio frequency magnetron sputtering, direct current magnetron sputtering, pulsed laser deposition or molecular beam epitaxy; the film prepared by chemical vapor deposition has poor continuity and high cost, and the functional layer grown by chemical vapor deposition is incompatible with the mainstream CMOS process, which further increases the cost of the device. Using metal targets containing yttrium and hafnium elements or corresponding oxide targets to grow the functional layer and using the above high-purity physical vapor methods for deposition can reduce the introduction of impurities in the resistive switching functional layer.

[0020] Furthermore, the growth power of the amorphous yttrium oxide film generation parameters is 20~200 W. Power below this range will lead to slow film growth rate and increased cost; power above this range will increase the roughness of the grown film and reduce the stability of the device. The growth time is 0.5~5 min. The film thickness prepared below this growth time is too thin and the resistive switching performance disappears; above this growth time range, the film is too thick and requires higher power to achieve data storage, which increases the power consumption of the device. The substrate heating temperature during the growth process is 100~500℃. The density of the film grown below this heating range is reduced and the device performance deteriorates; above this temperature range, the roughness of the functional layer film increases and the reliability of the memristor is reduced. During the growth process, a mixed gas of argon and oxygen is introduced, the growth gas pressure is 0.1~2 Pa, the argon flow rate is 5~35 sccm, and the oxygen flow rate is 5~35 sccm. When the growth pressure is lower than this range, and the argon and oxygen flow rates are lower than this range, the prepared yttrium oxide film is too thin and the storage window of the constructed memristor is small; when the growth pressure is higher than this range, and the argon and oxygen flow rates are higher than this range, the prepared film is too thick, resulting in an increase in the switching voltage, which affects the power consumption of the memristor.

[0021] Furthermore, the growth power of the amorphous hafnium oxide film is 30~350 W, which is the same as the yttrium oxide film above. If the power is lower than this range, the film growth rate will be too slow and the cost will increase; if the power is higher than this range, the roughness of the grown film will increase and the stability of the device will decrease. The growth time is 2~20 min, which is the same as the yttrium oxide film above. If the growth time is lower than this range, the film will be too thin and the resistive switching performance will disappear; if the growth time is higher than this range, the film will be too thick and higher power will be required to achieve data storage, which will increase the power consumption of the device. The substrate heating temperature during the growth process is 50~500℃, which is the same as the yttrium oxide film above. If the hafnium oxide film is grown below this heating range, the density will decrease and the device performance will deteriorate; if the hafnium oxide film is grown above this temperature range, the roughness will increase and the reliability of the memristor will decrease. During the growth process, a mixed gas of argon and oxygen is introduced, the growth gas pressure is 0.1~5 Pa, the argon flow rate is 10~80sccm, and the oxygen flow rate is 1~20 sccm. When the growth pressure is lower than this range, and the argon and oxygen flow rates are lower than this range, the prepared hafnium oxide film is thinner and the storage window of the memristor becomes smaller; when the gas pressure is higher than this range, and the argon and oxygen flow rates are higher than this flow rate, the prepared hafnium oxide film is thicker, resulting in a larger switching voltage for the operation of the memristor and ultimately a larger power consumption.

[0022] Furthermore, the thickness of the amorphous yttrium oxide film is 10~40 nm; the thickness of the hafnium oxide film is 20~80 nm. Although digital memristors with thicknesses below this range can achieve a high storage window, their stability and reliability are poor; above this range, the storage window is reduced, and digital memristors with high storage windows cannot be achieved.

[0023] Furthermore, the diameter of the circular mask is 20~300 μm. Above this range, the working current increases and the power consumption of the device increases. Below this diameter range, the stability of the constructed memristor deteriorates.

[0024] The present invention also discloses a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure obtained by the above preparation method, which comprises a bottom conductive electrode, a functional layer and an upper conductive electrode from bottom to top, and the functional layer is an amorphous yttrium oxide / hafnium oxide double-layer structure. Both amorphous yttrium oxide and amorphous hafnium oxide have abundant oxygen defects. By designing the amorphous yttrium oxide / hafnium oxide double-layer structure, the conductive filaments forming the resistive switching characteristics are regulated, thereby obtaining a memristor with a large storage window.

[0025] The present invention also discloses the application of the digital memristor based on the amorphous yttrium oxide / hafnium oxide double-layer structure prepared by the above-mentioned preparation method in a non-volatile resistive memory. The preparation method of the digital memristor with a high storage window has the advantages of simple structure construction, simple preparation process and low material cost. Compared with the memristor with a single hafnium oxide resistive layer, the yttrium oxide / hafnium oxide double-layer structure memristor exhibits stable digital resistive characteristics, especially has a larger storage window, which has important application prospects in high-performance, low-error data storage. In addition, by controlling the cut-off voltage and limiting the current at the same time, a multi-level storage capacity is presented, which has the potential advantage of high storage density while having a high storage window, and has good market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure obtained in embodiment 1 of the present invention.

[0027] Figure 2 The logarithmic current-voltage curve of a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure prepared in embodiment 1 of the present invention.

[0028] Figure 3 The current-voltage curves of a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure under different limiting currents prepared in embodiment 1 of the present invention.

[0029] Figure 4 The cyclic characteristic curve of a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure obtained in embodiment 1 of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings: The present invention discloses a method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure, comprising the following steps: 1) On a high-flatness device substrate, a first conductive film with high stability of a certain thickness is deposited by physical vapor deposition as the bottom conductive electrode of the memristor; 2) Using a physical vapor deposition method, using a target material containing yttrium and hafnium elements, on the bottom conductive electrode prepared in step 1), by controlling the growth parameters of the physical vapor deposition process such as substrate temperature, working gas pressure, ratio of argon and oxygen, deposition time and power, a high dielectric constant amorphous yttrium oxide film and an amorphous hafnium oxide film are sequentially deposited, and the thickness of the film is regulated to obtain an amorphous yttrium oxide / hafnium oxide double-layer structure as a functional layer of a high storage window digital memristor; 3) Using a circular mask of a certain diameter, a high-stability second conductive film of a certain thickness is further deposited on the amorphous yttrium oxide / hafnium oxide functional layer grown in step 2) as the upper conductive electrode of the memristor, thereby obtaining a digital memristor based on the amorphous yttrium oxide / hafnium oxide double-layer structure.

[0033] In step 1), the device substrate with high flatness is a polished single crystal silicon with a layer of silicon dioxide grown thereon or a highly transparent insulating glass.

[0034] In step 1) and step 3), the physical vapor deposition method is any one of thermal evaporation, electron beam evaporation and magnetron sputtering; the conductive film is any one of ITO, Pt, Au, W and TiN; and the thickness of the conductive electrode is 20~200 nm.

[0035] In step 2), the physical vapor deposition method is any one of radio frequency magnetron sputtering, direct current magnetron sputtering, pulsed laser deposition and molecular beam epitaxy; the target material containing yttrium and hafnium elements is a metal target material or a corresponding oxide target material.

[0036] In step 2), the growth power in the amorphous yttrium oxide film generation parameters is 20~200 W; the growth time is 0.5~5 min; the substrate heating temperature during the growth process is 100~500°C; a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 0.1~2 Pa, the argon flow rate is 5~35 sccm, and the oxygen flow rate is 5~35 sccm.

[0037] In step 2), the growth power of the amorphous hafnium oxide film is 30-350 W in the growth parameters; the growth time is 2-20 min; the substrate heating temperature is 50-500° C. during the growth process; a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 0.1-5 Pa, the argon flow rate is 10-80 sccm, and the oxygen flow rate is 1-20 sccm.

[0038] In step 2), the thickness of the amorphous yttrium oxide film is 10-40 nm; the thickness of the amorphous hafnium oxide film is 20-80 nm.

[0039] In step 3), the diameter of the circular mask is 20~300 μm.

[0040] The present invention also discloses the application of the digital memristor based on the amorphous yttrium oxide / hafnium oxide double-layer structure prepared by the above-mentioned preparation method in non-volatile memory. The yttrium oxide / hafnium oxide double-layer structure memristor exhibits stable digital resistive switching characteristics, especially has a large storage window, which has important application prospects in high-performance, low-error data storage. In addition, by controlling the cut-off voltage and limiting the current at the same time, it exhibits multi-level storage capacity, has the potential advantage of storage density while having a high storage window, and has good market application prospects.

[0041] The present invention discloses a method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure, comprising the following steps: 1) On a high-flatness device substrate, a first conductive film with high stability of a certain thickness is deposited by physical vapor deposition as the bottom conductive electrode of the memristor; Preferably, the device substrate with high flatness is polished single crystal silicon with a layer of silicon dioxide grown thereon or highly transparent insulating glass; the bottom conductive electrode is deposited by magnetron sputtering; the bottom conductive electrode is Pt; and the thickness of the bottom conductive electrode is 100 nm.

[0042] 2) using a physical vapor deposition method, using a target material containing yttrium and hafnium elements, depositing an amorphous yttrium oxide film with a high dielectric constant and an amorphous hafnium oxide film in sequence on the bottom conductive electrode prepared in step 1), thereby obtaining an amorphous yttrium oxide / hafnium oxide double-layer structure as a functional layer of a high storage window digital memristor; Preferably, the hafnium oxide and yttrium oxide films are grown by a physical vapor deposition method of radio frequency magnetron sputtering; the target material containing yttrium and hafnium elements is a metal target material; the growth power in the amorphous yttrium oxide film generation parameters is 100 W; the growth time is 2 min; the substrate heating temperature during the growth process is 300°C; argon and oxygen mixed gas is introduced during the growth process, the growth gas pressure is 0.5 Pa, the argon flow rate is 15 sccm, and the oxygen flow rate is 15 sccm; Preferably, the growth power in the amorphous hafnium oxide film generation parameters is 100 W; the growth time is 6 min; the substrate heating temperature during the growth process is 300° C.; a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 0.5 Pa, the argon flow rate is 45 sccm, and the oxygen flow rate is 5 sccm; Preferably, the thickness of the amorphous yttrium oxide film is 26 nm, and the thickness of the amorphous hafnium oxide film is 45 nm; Preferably, the diameter of the circular mask is 100 μm.

[0043] 3) Using a circular mask of a certain diameter, a high-stability conductive film of a certain thickness is further deposited on the grown yttrium oxide / hafnium oxide functional layer as the upper conductive electrode of the memristor, thereby obtaining a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure.

[0044] Preferably, a magnetron sputtering method is selected to deposit the upper conductive electrode; the upper conductive electrode is W; and the thickness of the upper conductive electrode is 100 nm.

[0045] Example 1 A method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure comprises the following steps: 1) On a polished single-crystal silicon substrate with a layer of silicon dioxide grown on a high flatness, a 100 nm thick high-stability Pt conductive film was deposited by magnetron sputtering as the bottom conductive electrode of the digital memristor; 2) Using the radio frequency magnetron sputtering method, using a metal target containing yttrium and hafnium elements, a high dielectric constant amorphous yttrium oxide film and an amorphous hafnium oxide film are sequentially deposited on the bottom conductive electrode. The parameters for the generation of the amorphous yttrium oxide film include a growth power of 100 W, a growth time of 2 min, a substrate heating temperature of 300°C during the growth process, a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 0.5 Pa, the argon flow rate is 15sccm, and the oxygen flow rate is 15sccm; the parameters for the generation of the amorphous hafnium oxide film include a growth power of 100 W, a growth time of 6 min, a substrate heating temperature of 300°C during the growth process, a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 0.5 Pa, the argon flow rate is 45sccm, and the oxygen flow rate is 5sccm. The thickness of the amorphous yttrium oxide film is 26 nm, and the thickness of the hafnium oxide film is 45 nm. The amorphous yttrium oxide / hafnium oxide double-layer structure is obtained as the functional layer of the digital memristor.

[0046] 3) Using a circular mask with a diameter of 100 μm, a 100 nm thick high-stability W conductive film was further deposited on the grown yttrium oxide / hafnium oxide double-layer structure functional layer by magnetron sputtering as the upper conductive electrode of the digital memristor, thus obtaining a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure.

[0047] See also Figure 1 , which is a schematic diagram of the structure of a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure prepared in Example 1 of the present invention. As can be seen from the figure, the prepared digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure comprises a bottom conductive electrode, a functional layer and an upper conductive electrode from bottom to top, and the functional layer is an amorphous yttrium oxide / hafnium oxide double-layer structure.

[0048] See also Figure 2 , is a logarithmic current-voltage curve of a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure prepared in Example 1 of the present invention. It can be seen from the figure that during multiple DC cycle tests, the digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure has stable digital characteristics and high stability.

[0049] See also Figure 3 , is the current-voltage curve of a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure under different limiting currents prepared in Example 1 of the present invention. It can be seen from the figure that multi-level storage capacity can be achieved by controlling different cut-off voltages.

[0050] See also Figure 4, is a cycle characteristic curve of a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure prepared in Example 1 of the present invention. It can be seen from the figure that the constructed digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure has no signs of decay in two hundred cycles and maintains a switching window greater than two orders of magnitude.

[0051] Example 2 A method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure comprises the following steps: 1) On a highly flat and transparent insulating glass substrate, a 20 nm thick highly stable ITO conductive film was deposited by thermal evaporation as the bottom conductive electrode of the digital memristor; 2) Using a DC magnetron sputtering method, a metal target containing yttrium and hafnium elements was used to sequentially deposit a high dielectric constant amorphous yttrium oxide film and an amorphous hafnium oxide film on the bottom conductive electrode. The parameters for the generation of the amorphous yttrium oxide film include a growth power of 100 W, a growth time of 2 min, a substrate heating temperature of 300°C during the growth process, a mixed gas of argon and oxygen was introduced during the growth process, the growth gas pressure was 0.5 Pa, the argon flow rate was 15 sccm, and the oxygen flow rate was 15 sccm; the parameters for the generation of the amorphous hafnium oxide film include a growth power of 100 W, a growth time of 6 min, a substrate heating temperature of 300°C during the growth process, a mixed gas of argon and oxygen was introduced during the growth process, the growth gas pressure was 0.5 Pa, the argon flow rate was 45 sccm, and the oxygen flow rate was 5 sccm. The thickness of the amorphous yttrium oxide film is 26 nm, and the thickness of the hafnium oxide film is 45 nm. The amorphous yttrium oxide / hafnium oxide double-layer structure was obtained as the functional layer of the digital memristor.

[0052] 3) Using a circular mask with a diameter of 20 μm, a 20 nm thick high-stability ITO conductive film was further deposited by thermal evaporation on the grown yttrium oxide / hafnium oxide double-layer structure functional layer as the upper conductive electrode of the digital memristor, thus obtaining a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure.

[0053] In Example 2, a highly flat insulating substrate is selected from highly transparent insulating glass, and a 20 nm thick high-stability ITO conductive film is deposited by thermal evaporation as the lower conductive electrode; a circular mask with a diameter of 20 μm is used to deposit a 20 nm thick high-stability ITO conductive film by thermal evaporation as the upper conductive electrode of the digital memristor, and a DC magnetron sputtering method is used to grow the functional layer. Compared with Example 1, using ITO as an electrode realizes the potential of controlling the resistive switching characteristics by light of a certain wavelength and intensity. At the same time, the thickness of the upper and lower electrodes is small, the size of the mask is small, and the stability of the memristor finally constructed is low.

[0054] Example 3 A method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure comprises the following steps: 1) On a polished single-crystal silicon substrate with a layer of silicon dioxide grown on a high flatness, a 200 nm thick high-stability W conductive film is deposited by electron beam evaporation as the bottom conductive electrode of the digital memristor; 2) Using the radio frequency magnetron sputtering method, using a metal target containing yttrium and hafnium elements, a high dielectric constant amorphous yttrium oxide film and an amorphous hafnium oxide film are sequentially deposited on the bottom conductive electrode. The parameters for the generation of the amorphous yttrium oxide film include a growth power of 100 W, a growth time of 2 min, a substrate heating temperature of 300°C during the growth process, a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 0.5 Pa, the argon flow rate is 15sccm, and the oxygen flow rate is 15sccm; the parameters for the generation of the amorphous hafnium oxide film include a growth power of 100 W, a growth time of 6 min, a substrate heating temperature of 300°C during the growth process, a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 0.5 Pa, the argon flow rate is 45sccm, and the oxygen flow rate is 5sccm. The thickness of the amorphous yttrium oxide film is 26 nm, and the thickness of the hafnium oxide film is 45 nm. The amorphous yttrium oxide / hafnium oxide double-layer structure is obtained as the functional layer of the high storage window digital memristor.

[0055] 3) Using a circular mask with a diameter of 300 μm, a 200 nm thick high-stability Pt conductive film was further deposited on the grown yttrium oxide / hafnium oxide double-layer structure functional layer using electron beam evaporation method as the upper conductive electrode of the digital memristor, thus obtaining a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure.

[0056] In Example 3, a 200 nm thick high-stability W conductive film is deposited as the bottom conductive electrode by electron beam evaporation; a 200 nm thick high-stability Pt conductive film is deposited as the top conductive electrode by electron beam evaporation using a circular mask with a diameter of 300 μm. Compared with Example 1, the electrode is deposited by electron beam evaporation, the thickness of the electrode is larger, the diameter of the mask is larger, and the operating voltage of the finally constructed memristor becomes larger, resulting in increased power consumption.

[0057] Example 4 A method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure comprises the following steps: 1) On a polished single-crystal silicon substrate with a layer of silicon dioxide grown on a high flatness, a 100 nm thick high-stability Au conductive film is deposited by magnetron sputtering as the bottom conductive electrode of the digital memristor; 2) Using a pulsed laser deposition method, using an oxide target containing yttrium and hafnium elements, a high dielectric constant amorphous yttrium oxide film and an amorphous hafnium oxide film are sequentially deposited on the bottom conductive electrode. The parameters for the generation of the amorphous yttrium oxide film include a growth power of 20 W, a growth time of 0.5 min, a substrate heating temperature of 100°C during the growth process, a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 0.1 Pa, the argon flow rate is 5 sccm, and the oxygen flow rate is 5 sccm. The parameters for the generation of the amorphous hafnium oxide film include a growth power of 30 W, a growth time of 2 min, a substrate heating temperature of 50°C during the growth process, a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 0.1 Pa, the argon flow rate is 10 sccm, and the oxygen flow rate is 1 sccm. The thickness of the amorphous yttrium oxide film is 10 nm, and the thickness of the hafnium oxide film is 20 nm. The amorphous yttrium oxide / hafnium oxide double-layer structure is obtained as the functional layer of the digital memristor.

[0058] 3) Using a circular mask with a diameter of 100 μm, a 100 nm thick high-stability Au conductive film is further deposited by magnetron sputtering on the grown yttrium oxide / hafnium oxide double-layer structure functional layer as the upper conductive electrode of the digital memristor, thereby obtaining a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure.

[0059] In Example 4, Au conductive film is used as the upper and lower electrodes, and the functional layer is deposited by pulsed laser deposition, and the growth parameters of amorphous yttrium oxide and amorphous hafnium oxide are at lower values, and the thickness of the prepared functional layer is smaller. Compared with Example 1, due to the smaller functional layer, although the transition voltage of the device is smaller, the stability of the constructed digital memristor is lower.

[0060] Example 5 A method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure comprises the following steps: 1) On a polished single-crystal silicon substrate with a layer of silicon dioxide grown on a high flatness, a 100 nm thick high-stability TiN conductive film is deposited by magnetron sputtering as the bottom conductive electrode of the digital memristor; 2) Using the molecular beam epitaxy method, a metal target containing yttrium and hafnium elements is used to sequentially deposit a high dielectric constant amorphous yttrium oxide film and an amorphous hafnium oxide film on the bottom conductive electrode. The parameters for the generation of the amorphous yttrium oxide film include a growth power of 200 W, a growth time of 5 min, a substrate heating temperature of 500°C during the growth process, a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 2 Pa, the argon flow rate is 35 sccm, and the oxygen flow rate is 35 sccm. The parameters for the generation of the amorphous hafnium oxide film include a growth power of 350 W, a growth time of 20 min, a substrate heating temperature of 500°C during the growth process, a mixed gas of argon and oxygen is introduced during the growth process, the growth gas pressure is 5 Pa, the argon flow rate is 80 sccm, and the oxygen flow rate is 20 sccm. . The thickness of the amorphous yttrium oxide film is 40 nm, and the thickness of the hafnium oxide film is 80 nm. An amorphous yttrium oxide / hafnium oxide double-layer structure is obtained as the functional layer of a high storage window digital memristor.

[0061] 3) Using a circular mask with a diameter of 100 μm, a 100 nm thick high-stability TiN conductive film is further deposited by magnetron sputtering on the grown yttrium oxide / hafnium oxide double-layer structure functional layer as the upper conductive electrode of the digital memristor, thereby obtaining a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure.

[0062] In Example 5, TiN conductive film is used as the upper and lower electrodes, and the functional layer is deposited by molecular beam epitaxy, and the growth parameters of amorphous yttrium oxide and amorphous hafnium oxide are at a larger value, and the thickness of the prepared functional layer is thicker. Compared with Example 1, due to the thicker functional layer, the transition voltage of the device is larger, thereby increasing power consumption.

[0063] In summary, the present invention discloses a method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure, which has the following characteristics: 1) The present invention proposes a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure, and the preparation method thereof has the advantages of simple structure construction, simple preparation process and low material cost.

[0064] 2) Compared with the memristor with a single hafnium oxide resistive layer, the digital memristor based on the amorphous yttrium oxide / hafnium oxide double-layer structure exhibits stable digital resistive characteristics, especially a larger storage window, which makes it have important application prospects in high-performance, low-error data storage.

[0065] 3) By controlling the cut-off voltage and limiting the current, it presents multi-level storage capability, has the potential advantage of high storage density while having a high storage window, and has good market application prospects.

[0066] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure, characterized in that: The steps include: 1) On a highly flat substrate, a first conductive film is deposited by physical vapor deposition as a bottom conductive electrode of a digital memristor; 2) using a target material containing yttrium and a target material containing hafnium, on the bottom conductive electrode prepared in step 1), sequentially depositing an amorphous yttrium oxide film and an amorphous hafnium oxide film by physical vapor deposition to obtain an amorphous yttrium oxide / hafnium oxide double-layer structure as a functional layer of a digital memristor; 3) Using a mask, a second conductive film is deposited on the functional layer prepared in step 2) by physical vapor deposition as an upper conductive electrode of the digital memristor, thereby obtaining a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure.

2. The method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure according to claim 1, characterized in that: In step 1), the high-flatness substrate is polished single-crystal silicon grown with silicon dioxide or highly transparent insulating glass.

3. The method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure according to claim 1, characterized in that: In step 1), the physical vapor deposition method is any one of thermal evaporation, electron beam evaporation and magnetron sputtering; the first conductive film is any one of ITO, Pt, Au, W and TiN; the thickness of the bottom conductive electrode is 20~200 nm.

4. The method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure according to claim 1, characterized in that: In step 2), the physical vapor deposition method is any one of radio frequency magnetron sputtering, direct current magnetron sputtering, pulsed laser deposition and molecular beam epitaxy; the target material containing yttrium element is a metal target material or a corresponding oxide target material; the target material containing hafnium element is a metal target material or a corresponding oxide target material.

5. The method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure according to claim 1, characterized in that: In step 2), the growth power of the amorphous yttrium oxide film during deposition is 20-200 W; the growth time is 0.5-5 min; the substrate heating temperature is 100-500° C. during the growth process; a mixed gas of argon and oxygen is introduced during the growth process; the growth gas pressure is 0.1-2 Pa, the argon flow rate is 5-35 sccm; and the oxygen flow rate is 5-35 sccm.

6. The method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure according to claim 1, characterized in that: In step 2), the growth power during the deposition of the amorphous hafnium oxide film is 30-350 W; the growth time is 2-20 min; the substrate heating temperature during the growth process is 50-500° C.; a mixed gas of argon and oxygen is introduced during the growth process; the growth gas pressure is 0.1-5 Pa, the argon flow rate is 10-80 sccm, and the oxygen flow rate is 1-20 sccm.

7. The method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure according to claim 1, characterized in that: In step 2), the thickness of the amorphous yttrium oxide film is 10-40 nm; the thickness of the amorphous hafnium oxide film is 20-80 nm.

8. The method for preparing a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure according to claim 1, characterized in that: In step 3), the mask is a circular mask, and the diameter of the circular mask is 20-300 μm; the physical vapor deposition method is any one of thermal evaporation, electron beam evaporation and magnetron sputtering; the second conductive film is any one of ITO, Pt, Au, W and TiN; the thickness of the upper conductive electrode is 20-200 nm.

9. A digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure, characterized in that: The device is prepared by the preparation method according to any one of claims 1 to 8, and comprises, from bottom to top, a bottom conductive electrode, a functional layer and an upper conductive electrode, wherein the functional layer is an amorphous yttrium oxide / hafnium oxide double-layer structure.

10. Application of a digital memristor based on an amorphous yttrium oxide / hafnium oxide double-layer structure prepared by the preparation method according to any one of claims 1 to 8 in a non-volatile resistive random access memory.

Images