Volatile resistive random access device and preparation method thereof

Abstract

The invention discloses a volatile resistive device and a preparation method thereof, the resistive device is an oxygen vacancy type volatile resistive device and comprises a first electrode layer, a buffer layer, a resistive layer and a second electrode layer which are stacked in sequence, the first electrode layer is made of transition metal, and the buffer layer is made of oxide corresponding to the transition metal; the resistive layer has a higher oxygen vacancy concentration than the buffer layer. In the preparation process of the device, a large number of oxygen vacancy defects exist in the grown resistive layer by adjusting oxygen partial pressure or oxygen atmosphere concentration, and an oxygen vacancy concentration difference is formed between the resistive layer and the buffer layer, so that the operation voltage is reduced, and the power consumption of the device is reduced; and moreover, the buffer layer is grown by using the metal oxide target material, so that the preparation uniformity is improved, and the electrical stability of the device is improved. The resistive device has excellent low power consumption characteristic and stability, and has good application potential in the fields of artificial intelligence, neuromorphic calculation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of resistive switching devices, and in particular to a volatile resistive switching device and a preparation method thereof. Background Art

[0002] With the development of artificial intelligence and big data technology and applications, more advanced large-scale data storage solutions are in urgent need of replacement. Resistive switching devices have attracted widespread attention due to their advantages such as simple structure, high integration, low power consumption, and compatibility with CMOS processes. They have been applied to the fields of neuromorphic computing and memory, and are expected to form a new generation of storage solutions based on them. According to whether the data can be preserved for a long time after power failure, resistive switching devices are divided into two categories: non-volatile and volatile. The retention time of volatile resistive switching devices is in the range of nanoseconds to milliseconds. After disconnecting the external stimulus, the low resistance state (corresponding to logic "0") will return to the high resistance state (corresponding to logic "1"). In recent years, researchers have developed a variety of volatile resistive switching devices based on metal ion conductive channels. However, metal ion resistive switching devices that form conductive channels through metal ions face many problems, such as requiring higher operating voltages and showing poor stability and durability. Therefore, oxygen vacancy resistive switching devices with better durability and lower power consumption have attracted widespread attention from researchers, but the oxygen vacancy principle is mostly used for non-volatile resistive switching devices, and there are few reports on researchers using the oxygen vacancy principle to prepare volatile resistive switching devices.

[0003] In summary, the preparation of oxygen vacancy volatile resistive switching devices with high stability and excellent electrical properties is still a major challenge. Therefore, it is necessary to provide a simplified preparation method for resistive switching devices to optimize the electrical properties of existing volatile resistive switching device solutions. Summary of the invention

[0004] The object of the present invention is to provide a volatile resistive switching device and a preparation method thereof, so as to solve the problems of high power consumption and poor durability of the volatile resistive switching device in the prior art, and at the same time increase the uniformity of the preparation of the resistive switching device.

[0005] The present invention provides a volatile resistive switching device using the oxygen vacancy principle, comprising a first electrode layer and a second electrode layer, and a resistive switching layer and a buffer layer located between the first electrode layer and the second electrode layer, wherein the first electrode layer is selected from a transition metal material, and the buffer layer material should be selected from an oxide corresponding to the transition metal material of the first electrode layer, so that the first electrode layer and the buffer layer can be mutually converted in a small range on a contact interface through an oxidation-reduction reaction under the action of an electric field to achieve the volatile characteristics of the resistive switching device; the resistive switching layer material can be a metal oxide, and the oxygen vacancy concentration of the resistive switching layer is required to be greater than that of the buffer layer, and the oxygen vacancy concentration difference between the resistive switching layer and the buffer layer is beneficial to improving the electrical characteristics of the resistive switching device.

[0006] Preferably, the thickness of the resistive layer is 10 nm to 30 nm, and the thickness of the buffer layer is 5 nm to 10 nm. Further preferably, in the resistive layer and the buffer layer, the thickness of the resistive layer with a higher oxygen vacancy concentration is greater than that of the buffer layer.

[0007] The dielectric materials of the resistive layer and the buffer layer can be metal oxides, including but not limited to: hafnium oxide (HfO x ), tantalum oxide (TaO x ), titanium oxide (TiO x ), nickel oxide (NiO x ), etc., the oxygen vacancy concentrations of the resistive layer and the buffer layer are different, wherein the resistive layer should obtain more oxygen vacancies by controlling the oxygen partial pressure or the oxygen atmosphere concentration during the preparation process; the buffer layer material should be selected from the metal oxide material corresponding to the first electrode layer. In some embodiments of the present invention, the resistive layer is HfO with a high oxygen vacancy defect density. x The buffer layer is a Ta2O5 film with a low oxygen vacancy defect density, and the first electrode layer is a metal Ta. In other embodiments, the resistive layer is a HfO film with a high oxygen vacancy defect density. x The buffer layer is a TiO2 film with a low oxygen vacancy defect density, and the first electrode layer is metal Ti.

[0008] In the above-mentioned volatile resistive device, the second electrode layer is preferably made of an inert metal material or a metal nitride material, and can be made of an inert metal such as Pt (platinum), Pd (palladium), Ta (tantalum), or a metal alloy such as TiN (titanium nitride) or TaN (tantalum nitride).

[0009] The first electrode layer is a transition metal material, and can be made of transition metals such as Ti (titanium), Ta (tantalum), Mo (molybdenum), Ni (nickel), and W (tungsten); correspondingly, the buffer layer material is TiO2, Ta2O5, MoO3, NiO, and WO3.

[0010] Preferably, the thickness of the first electrode layer and the second electrode layer ranges from 20 nm to 100 nm.

[0011] refer to Figure 2 In the process of preparing the resistive switching layer of the volatile resistive switching device of the present invention, the oxygen partial pressure or the oxygen concentration of the atmosphere is adjusted to make the oxidation reaction incomplete, resulting in a large number of oxygen vacancy defects (corresponding to Figure 2 The solid circle in the figure), and the oxygen vacancy concentration in the resistive switching layer is higher than that in the buffer layer, forming a concentration difference. When the volatile resistive switching device is working, when an excitation is applied between the first electrode layer and the second electrode layer, the device undergoes a resistive switching process; under the action of the electric field, the oxygen ions in the resistive switching layer (corresponding to Figure 4The dotted circle in the figure) and oxygen vacancies migrate regularly in opposite directions, thereby forming a conductive channel between the first electrode layer and the second electrode layer, and the volatile resistive switching device presents a low resistance state; under the action of the external electric field excitation, a metal-oxide interface layer is formed between the first electrode layer and the buffer layer. Due to the matching between the electrode material and the buffer layer material, the interface layer will affect the tunneling and transmission effect of electrons, thereby affecting the conversion between oxygen ions and oxygen vacancies, thereby affecting the switching of the conductive channel; when the external voltage is removed, the oxygen vacancies near the interface layer combine with the oxygen ions, so that the conductive channel near the interface layer is disconnected, and the volatile resistive switching device presents a high resistance state. Compared with the common metal ion volatile resistive switching device, the oxygen vacancy type volatile resistive switching device of the present invention exhibits lower operating voltage and power consumption due to the oxygen vacancy concentration difference and the characteristics of the oxygen vacancy type resistive switching device itself; and because the buffer layer with low oxygen vacancies is prepared using a metal oxide target material during preparation, the prepared resistive switching device has excellent uniformity.

[0012] The present invention provides a method for preparing the above-mentioned volatile resistive switching device ( Figure 3 ),include:

[0013] (1) forming a first electrode layer on a substrate;

[0014] (2) coating a photoresist on the first electrode layer, and exposing and developing the photoresist according to a preset pattern to form a pattern area on the first electrode layer;

[0015] (3) growing a thin film on the patterned area by physical vapor deposition using a metal oxide target to form a buffer layer;

[0016] (4) growing a resistive switching layer having a high oxygen vacancy defect density on the buffer layer by chemical vapor deposition or physical vapor deposition and controlling the oxygen partial pressure or oxygen concentration in the atmosphere;

[0017] (5) forming a second electrode layer on the resistive layer;

[0018] (6) Removing the photoresist.

[0019] According to the method for preparing a volatile resistive switching device provided by the present invention, the resistive switching layer dielectric material can be selected from binary metal oxides, doped metal oxides, etc., and the buffer layer material should be selected from a metal oxide material corresponding to the first electrode layer to form a matching metal-oxide interface layer between the first electrode layer and the buffer layer. The resistive switching layer dielectric material and the buffer layer dielectric material can be the same or different, provided that the oxygen vacancy concentrations of the resistive switching layer and the buffer layer are different.

[0020] In the above step (4), if physical vapor deposition is used, the resistive layer should be grown in an environment filled with argon and oxygen according to a preset oxygen partial pressure, wherein the oxygen partial pressure is usually set at 0%-50%, and the target material can be a metal or a metal oxide; if chemical vapor deposition is used, organic compounds of metals such as titanium, tantalum, hafnium, nickel, etc. can be selected as metal sources, and combined with oxygen sources such as oxygen or water vapor to grow low-temperature films within 100°C.

[0021] Preferably, in the above step (3), the buffer layer is formed by sputtering a transition metal oxide target in an argon-filled environment. The transition metal oxide target can be selected from metal oxides such as Ta2O5, TiO2, WO3, MoO3, NiO, etc. to ensure the uniformity of the buffer layer film.

[0022] In the above step (1), the substrate may be a Si substrate or a Si / SiO2 composite substrate.

[0023] In some embodiments of the present invention, before preparing the first electrode layer, the method further comprises:

[0024] thermally oxidizing the silicon wafer to form a silicon dioxide insulating layer on the silicon wafer;

[0025] An adhesion layer is formed on the silicon dioxide insulating layer by magnetron sputtering.

[0026] The silicon dioxide insulation layer generated on the surface of the silicon wafer after oxidation effectively isolates the device from the bottom silicon wafer, which can effectively reduce current leakage and parasitic capacitance to improve electrical performance. The adhesion layer formed on the silicon dioxide insulation layer by magnetron sputtering helps to improve the adhesion between the silicon dioxide insulation layer and the first electrode layer, thereby improving the mechanical strength of the device.

[0027] The volatile resistive switching device prepared by the present invention can form an oxygen vacancy concentration difference between the resistive switching layer and the buffer layer by controlling the oxygen partial pressure or the oxygen atmosphere concentration to control the oxygen vacancy concentration, which is beneficial to reducing the operating voltage and reducing the power consumption of the device. In addition, the method of using a metal oxide target to grow the buffer layer is beneficial to improving the uniformity of the prepared device and improving the electrical stability of the device. Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) By inserting a resistive switching layer and a buffer layer between the first electrode layer and the second electrode layer, when an excitation voltage is applied between the first electrode layer and the second electrode layer, the concentration difference of oxygen vacancies between the resistive switching layer and the buffer layer is conducive to the interlayer migration of oxygen vacancies, thereby ensuring a lower operating voltage and reducing the power consumption of the resistive switching device. In addition, since matching materials are selected between the first electrode layer and the buffer layer, the metal-oxide interface layer formed affects the tunneling and transmission effect of electrons, thereby affecting the conversion between oxygen ions and oxygen vacancies, making the resistive switching device volatile.

[0029] (2) The resistive layer regulates the oxygen vacancy concentration by controlling the oxygen partial pressure or the oxygen concentration in the atmosphere, giving the resistive device the flexibility to adjust its performance; the buffer layer uses metal oxide targets to increase the uniformity of the resistive device preparation, ensure consistent oxygen vacancy concentration, and improve the reliability of the resistive device. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the volatile resistive switching device provided by the present invention.

[0031] Figure 2 It is a schematic diagram of the process of realizing the function of the volatile resistive switching device provided by the present invention.

[0032] Figure 3 It is a preparation flow chart of the volatile resistive switching device of the present invention.

[0033] Figure 4 This is a flow chart of preparing a volatile resistive switching device according to Example 1 of the present invention.

[0034] Figure 5 This is a flow chart of preparing a volatile resistive switching device according to Example 2 of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described through embodiments in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figure 4 As shown, a volatile resistive switching device is prepared according to the following steps:

[0038] After thermal oxidation of the single-side polished silicon wafer, a 300nm SiO2 insulating layer is generated on the surface, and a 30nm metal Ti is formed as an adhesion layer on the SiO2 insulating layer by DC magnetron sputtering;

[0039] Depositing 100 nm of Ta as the first electrode layer on the adhesion layer by DC magnetron sputtering;

[0040] Coating a photoresist on the first electrode layer, and forming a preset pattern on a preset area of ​​the first electrode layer through exposure and development;

[0041] By physical vapor deposition, in an argon environment, Ta2O5 target material is used to deposit Ta2O5 on the first electrode layer to form a 5nm buffer layer;

[0042] By atomic layer deposition, in an argon environment, tetrakis(dimethylamino)hafnium (TDMAH) and H2O were used as precursor sources, and low-temperature deposition was performed at 90°C to form a 10nm HfO2 film with high oxygen vacancy defect density as a resistive layer.

[0043] On the resistive layer, a metal Pt target is used to deposit 50 nm of metal Pt as the second electrode layer by DC magnetron sputtering.

[0044] Ultrasonic stripping is used to remove excess photoresist to expose the first electrode layer area.

[0045] Example 2

[0046] like Figure 5 As shown, a volatile resistive switching device is prepared according to the following steps:

[0047] After thermal oxidation of the single-side polished silicon wafer, a 300nm SiO2 insulating layer is generated on the surface, and a 30nm TiN is formed on the SiO2 insulating layer by DC magnetron sputtering as an adhesion layer;

[0048] On the adhesion layer, 100 nm of Ti was deposited as the first electrode layer by DC magnetron sputtering;

[0049] Coating a photoresist on the first electrode layer, and forming a preset pattern on a preset area of ​​the first electrode layer through exposure and development;

[0050] By physical vapor deposition, in an argon environment, a TiO2 target was used to deposit a 7nm TiO2 film as a buffer layer on the first electrode layer;

[0051] By atomic layer deposition, TDMAH and H2O were used as precursor sources in an argon environment, and low-temperature deposition was performed at 90°C to form a 15nm HfO2 film with high oxygen vacancy defect density as a resistive layer.

[0052] On the resistive layer, a metal W target is used to deposit 50 nm of metal W as the second electrode layer by DC magnetron sputtering.

[0053] Ultrasonic stripping is used to remove excess photoresist to expose the first electrode layer area.

[0054] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0055] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A volatile resistive switching device, comprising a first electrode layer, a buffer layer, a resistive switching layer and a second electrode layer stacked in sequence, characterized in that: The volatile resistive switching device is an oxygen vacancy type volatile resistive switching device, wherein the material of the first electrode layer is a transition metal, the material of the buffer layer is an oxide corresponding to the transition metal; the resistive switching layer has a higher oxygen vacancy concentration than the buffer layer.

2. The volatile resistive switching device according to claim 1, characterized in that: The thickness of the resistive layer is 10 nm to 30 nm, the thickness of the buffer layer is 5 nm to 10 nm, and the thickness of the resistive layer is greater than that of the buffer layer.

3. The volatile resistive switching device according to claim 1, characterized in that: The material of the first electrode layer is selected from Ti, Ta, Mo, Ni, and W, and correspondingly, the material of the buffer layer is TiO2, Ta2O5, MoO3, NiO, and WO3.

4. The volatile resistive switching device according to claim 1, characterized in that: The resistive switching layer is a binary metal oxide or a doped metal oxide.

5. The volatile resistive switching device according to claim 1, characterized in that: The resistive switching layer is a hafnium oxide, tantalum oxide, titanium oxide or nickel oxide film.

6. The method for preparing the volatile resistive switching device according to any one of claims 1 to 5, comprising the following steps: 1) forming a first electrode layer on a substrate; 2) coating a photoresist on the first electrode layer, exposing and developing the layer according to a preset pattern, and forming a pattern area on the first electrode layer; 3) growing a thin film on the patterned area by physical vapor deposition using a metal oxide target to form a buffer layer; 4) Using chemical vapor deposition or physical vapor deposition on the buffer layer, growing a resistive switching layer with a high oxygen vacancy defect density by controlling the oxygen partial pressure or oxygen atmosphere concentration; 5) forming a second electrode layer on the resistive layer; 6) Remove the photoresist.

7. The preparation method according to claim 6, characterized in that: Step 3) forming the buffer layer by sputtering a transition metal oxide target in an argon atmosphere.

8. The preparation method according to claim 6, characterized in that: Step 4) In a mixed atmosphere of argon and oxygen, a resistive switching layer is grown by physical vapor deposition according to a preset oxygen partial pressure.

9. The preparation method according to claim 6, characterized in that: Step 4) using a metal organic compound as a metal source and oxygen or water vapor as an oxygen source, a low temperature resistive layer is grown by chemical vapor deposition.

10. The preparation method according to claim 6, characterized in that: A silicon wafer is used as a substrate, the silicon wafer is first thermally oxidized to form a silicon dioxide insulating layer on the silicon wafer, an adhesion layer is then formed on the silicon dioxide insulating layer by magnetron sputtering, and a first electrode layer is prepared on the adhesion layer.

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