Mn-doped gallium oxide-based resistive random access memory and preparation method thereof

Abstract

The application provides a resistance change memory based on Mn-doped gallium oxide and a preparation method thereof. 3 The resistance change memory with a sandwich structure (Pt / a-GMO / Pt) prepared by using the thin film has a high resistance to low resistance ratio (R OFF / R ON ) of more than 10 , and obvious magnetization change is accompanied by resistance switching. The method for preparing the Mn-doped amorphous gallium oxide thin film is simple and easy to implement, and can be applied to resistance change memories and multifunctional memory devices, and has wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor materials and devices, and particularly to a Mn-doped gallium oxide-based resistive random access memory and a preparation method thereof. BACKGROUND

[0002] Resistive random access memory (RRAM or ReRAM, also known as memristor) is one of the most promising new non-volatile memory technologies, which has simple device structure, simple operation mode, easy size reduction, high speed, low energy consumption, low cost, easy compatibility with CMOS process and many other characteristics. The emergence of resistive random access memory is widely considered as an opportunity to design new devices and store higher density information and simulate synaptic connections in artificial intelligence neural networks. Recently, resistive random access memory (RRAM) has attracted widespread interest as one of the most important potential memristor applications due to its excellent functionality, simple manufacturing, low power consumption and electrical characteristics in the system. Resistive random access memory is usually composed of a metal / insulating layer / metal sandwich structure, the metal layer is the upper and lower electrode, and the middle insulating layer is the resistive random access memory material. Various oxides, nitrides and sulfides have been studied as switching layers in RRAM, among which gallium oxide is one of the ideal candidate materials due to its good bipolar resistance switching characteristics and chemical stability.

[0003] One of the key parameters of RRAM is the R OFF / R ON ratio, which determines whether the stored information (resistance state) can be distinguished as binary bits "1" or "0" by the peripheral circuit in a changing environment. A high R OFF / R ON ratio ensures a lower data read / write error rate. So far, the R OFF / R ON ratio of gallium oxide-based RRAM is usually between 2-10 2 . For example, the R OFF / R ON ratio of Au / β-Ga2O3 / Au structure prepared by vapor-liquid-solid (VLS) is only 10, while the R x / ITO structure prepared by pulsed laser deposition (PLD) and indium gallium zinc oxide (IGZO) / amorphous Ga2O3 / IGZO structure prepared by radio frequency magnetron sputtering have R OFF / R ON ratio of about 10 2 . Since the additional embedded layer improves the current-voltage (I-V) characteristics, gallium oxide-based structures such as Pt / a-Ga2O3 / ZnO x / Pt and Pt / a-GaO xR of resistive switching memory of semiconductor heterostructure (SHS) consisting of GaO / MnOx / SiC / Pt OFF / R ON The ratio can be increased to about 10 3 However, the manufacture of SHSs requires complex processes and sophisticated techniques.

[0004] In addition, in magnetic semiconductor devices, magnetic doping also plays a key role because it can design spin / charge degrees of freedom to adjust the magnetic moment / resistance of the semiconductor. In view of the importance of doping technology, it is very attractive to establish a doping method for emerging semiconductor-based resistive switching memory, which will simplify the difficulty and cost of manufacturing the above-mentioned various self-propagating semiconductors. Therefore, it is urgent to find a new, simple and convenient method to prepare a high-R OFF / R ON ratio and pure gallium oxide-based resistive switching memory without SHSs. SUMMARY

[0005] The purpose of the present application is to provide a Mn-doped gallium oxide-based resistive switching memory and a preparation method thereof to solve the problem of the low R OFF / R ON or complex manufacturing process. The preferred technical solutions of the many technical solutions provided by the present application can produce many technical effects, which are described in detail below.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] The preparation method of the Mn-doped gallium oxide-based resistive switching memory provided by the present application comprises the following steps:

[0008] Step S1: preparing a GaMn precursor solution: adding 1-100 parts by mass of a Mn precursor solution to 100 parts by mass of a Ga precursor solution, and fully stirring to obtain a GaMn precursor solution;

[0009] The preparation method of the Ga precursor solution comprises: adding 2-15 parts by mass of polyethyleneimine and 2-15 parts by mass of ethylenediaminetetraacetic acid to 100 parts by mass of deionized water, fully stirring until clear to obtain a polymer aqueous solution, then adding 1-10 parts by mass of a soluble gallium salt to the polymer aqueous solution, fully stirring until uniform, and ultrafiltrating molecules with a molecular weight less than 10,000 g / mol and concentrating to obtain the Ga precursor solution;

[0010] The preparation method of the Mn precursor solution comprises: adding 2-15 parts by mass of polyethyleneimine and 2-15 parts by weight of ethylenediaminetetraacetic acid into 100 parts by weight of deionized water, stirring sufficiently until clear to obtain a polymer aqueous solution, then adding 1-10 parts by weight of a soluble manganese salt into the polymer aqueous solution, stirring uniformly, removing molecules with a molecular weight less than 10,000 g / mol by ultrafiltration, and concentrating to obtain the Mn precursor solution.

[0011] Step S2: cleaning the substrate surface: taking Si / SiO2 / Pt as the substrate, cleaning in acetone, alcohol, and deionized water respectively by ultrasonic wave for 10-15 min, and finally blowing dry with nitrogen;

[0012] Step S3: spin coating: spin coating the GaMn precursor solution obtained in step S1 onto the substrate cleaned in step S2 to obtain a preformed film;

[0013] Step S4: heat treatment: placing the preformed film obtained in step S3 in an oxidizing atmosphere at a temperature of 480-580 ℃ to perform heat treatment, thereby obtaining a Mn-doped amorphous gallium oxide film;

[0014] Step S5: preparing a top electrode: growing an inert metal electrode on the surface of the Mn-doped amorphous gallium oxide film covered with a metal mask by electron beam evaporation, thereby preparing a sandwich-structured resistive random access memory.

[0015] According to a preferred embodiment, in step S2, the cleaning step of the substrate comprises: sequentially cleaning in acetone, alcohol, and deionized water by ultrasonic wave, and finally blowing dry with nitrogen.

[0016] According to a preferred embodiment, in step S3, the spin coating step further comprises: adjusting the rotation speed and the number of spin coating to adjust the thickness of the prepared film.

[0017] According to a preferred embodiment, in the multiple spin coating process, the preformed film is prepared by repeatedly performing step S3 and then performing step S4, or by alternately performing step S3 and step S4.

[0018] According to a preferred embodiment, in step S4, the oxidizing atmosphere contains oxygen, and the oxygen content is 10%-100%.

[0019] According to a preferred embodiment, in step S5, the inert metal electrode grown on the surface of the Mn-doped amorphous gallium oxide film is an Au or Pt electrode.

[0020] According to a preferred embodiment, the electrode diameter of the inert metal electrode is 50-300 nm, the shape of the inert metal electrode is circular or square, and the thickness of the inert metal electrode is 50-1000 nm.

[0021] The application further provides a resistance change memory based on Mn-doped gallium oxide, which is prepared by the preparation method and comprises a substrate layer, a Mn-doped amorphous gallium oxide film layer and a top electrode, wherein the substrate layer is a Si / SiO2 / Pt substrate, the Mn-doped amorphous gallium oxide film layer is arranged above the substrate layer, and the top electrode is arranged above the Mn-doped amorphous gallium oxide film layer.

[0022] Based on the above technical solution, the resistance change memory based on Mn-doped gallium oxide and the preparation method thereof have at least the following technical effects:

[0023] The preparation method has low requirements on the environment, does not need a vacuum environment and airtightness, and can react in air, so that the cost can be greatly reduced. The Mn-doped amorphous gallium oxide film prepared by the application has good surface flatness, which is beneficial to the preparation of devices.

[0024] On the other hand, the Pt / a-GMO / Pt resistance change memory prepared by the application embodiment shows a bipolar resistance change behavior, does not need an electroforming process, and can eliminate a high-voltage source in the design of a storage circuit. The Pt / a-GMO / Pt resistance change memory prepared by the application embodiment has almost no degradation after 150 cycles, and can ensure that the switching between HRS and LRS has high repeatability and reliability. The Pt / a-GMO / Pt resistance change memory prepared by the application embodiment remains good for up to 10 3 s of time. The magnetization of the Pt / a-GMO / Pt resistance change memory prepared by the application embodiment changes with the resistance state, indicating that there is a significant magnetoelectric effect. The R OFF / R ON of the Pt / a-GMO / Pt resistance change memory prepared by the application embodiment is up to 10 3 , so that the peripheral circuit is easy to distinguish the storage information. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Figure 1 is an atomic force microscope (AFM) image of the Mn-doped amorphous gallium oxide film prepared in the application embodiment 1.

[0027] Figure 2is a high-resolution transmission electron microscope (HRTEM) image of the Mn-doped amorphous gallium oxide thin film prepared in Example 1 of the present application.

[0028] Figure 3 is a structural schematic diagram of a Pt / a-GMO / Pt resistive random access memory with a sandwich structure prepared in Example 1 of the present application.

[0029] Figure 4 is a curve diagram of typical bipolar resistive switching behavior of a Pt / a-GMO / Pt resistive random access memory prepared in Example 1 of the present application.

[0030] Figure 5 is a retention time analysis result of a Pt / a-GMO / Pt resistive random access memory prepared in Example 1 of the present application.

[0031] Figure 6 is a retention time analysis result of a Pt / a-GMO / Pt resistive random access memory prepared in Example 1 of the present application.

[0032] Figure 7 is a hysteresis loop in a low resistance state and a high resistance state of a Pt / a-GMO / Pt resistive random access memory prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0033] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0034] The present application provides a preparation method of a resistive random access memory based on Mn-doped gallium oxide, comprising the following steps:

[0035] Step S1: preparing a GaMn precursor solution: adding 1-100 parts by mass of a Mn precursor solution to 100 parts by mass of a Ga precursor solution, and fully stirring to obtain a GaMn precursor solution.

[0036] The preparation method of the Ga precursor solution comprises: adding 2-15 parts by mass of polyethyleneimine and 2-15 parts by mass of ethylenediaminetetraacetic acid to 100 parts by mass of deionized water, fully stirring until clear to obtain a polymer aqueous solution, then adding 1-10 parts by mass of a soluble gallium salt to the polymer aqueous solution, fully stirring until uniform, and ultrafiltrating molecules with a molecular weight less than 10,000 g / mol and concentrating to obtain the Ga precursor solution.

[0037] The preparation method of the Mn precursor solution comprises the following steps: adding 2-15 parts by mass of polyethylene imine and 2-15 parts by weight of ethylenediaminetetraacetic acid into 100 parts by weight of deionized water, fully stirring to obtain a polymer aqueous solution, then adding 1-10 parts by weight of a soluble manganese salt into the polymer aqueous solution, fully stirring to be uniform, removing molecules with a molecular weight less than 10000 g / mol by ultrafiltration, and concentrating to obtain the Mn precursor solution.

[0038] Step S2: cleaning the substrate surface: taking Si / SiO2 / Pt as the substrate, cleaning the substrate in acetone, alcohol, and deionized water in sequence by ultrasonic cleaning for 10-15 min, and finally blowing dry with nitrogen.

[0039] Step S3: spin coating: spin coating the GaMn precursor solution obtained in step S1 onto the substrate cleaned in step S2 to obtain a pre-fabricated film; the thickness of the prepared film can be adjusted by adjusting the rotation speed and the number of spin coating; in the process of multiple spin coating, the pre-fabricated film can be prepared by repeatedly performing step S3 and then performing step S4, or by alternately performing step S3 and step S4.

[0040] Step S4: heat treatment: placing the pre-fabricated film obtained in step S3 in an oxidizing atmosphere at a temperature of 480-580 ℃ to perform heat treatment, to obtain a Mn-doped amorphous gallium oxide film; the oxidizing atmosphere contains oxygen, and the oxygen content is 10%-100%.

[0041] Step S5: preparing a top electrode: growing an inert metal electrode on the surface of the Mn-doped amorphous gallium oxide film covered with a metal mask by electron beam evaporation, to prepare a sandwich-structured resistive random access memory; in this step, the inert metal electrode grown on the surface of the Mn-doped amorphous gallium oxide film is an Au or Pt electrode. Preferably, the electrode diameter of the inert metal electrode is 50-300 nm. The shape of the inert metal electrode is circular or square. The thickness of the inert metal electrode is 50-1000 nm.

[0042] Example 1

[0043] The embodiment provides a preparation method of a resistive random access memory based on Mn-doped gallium oxide, comprising the following steps:

[0044] Step S1: preparing a Ga precursor solution: adding 10 parts by mass of polyethylene imine (PEI) and 10 parts by mass of ethylenediaminetetraacetic acid (EDTA) into 100 parts by mass of deionized water, fully stirring to obtain a polymer aqueous solution, then adding 5 parts by mass of gallium nitrate hydrate Ga(NO3)3·xH2O into the polymer aqueous solution, fully stirring to be uniform, removing molecules with a molecular weight less than 10000 g / mol by ultrafiltration, and concentrating to obtain the Ga precursor solution.

[0045] Preparation of Mn precursor solution: 10 parts by mass of polyethyleneimine (PEI) and 10 parts by mass of ethylenediaminetetraacetic acid (EDTA) were added to 100 parts by mass of deionized water, and the mixture was stirred until clear to obtain a polymer aqueous solution. Then, 5 parts by mass of manganese chloride was added to the polymer aqueous solution and stirred until uniform. The solution was subjected to ultrafiltration to remove molecules with a molecular weight of less than 10,000 g / mol, and concentrated to obtain a Mn precursor solution.

[0046] Preparation of GaMn precursor solution: 10 parts of the Mn precursor solution was added to 100 parts by mass of the Ga precursor solution, and the mixture was stirred until clear to obtain a GaMn precursor solution.

[0047] Step S2: cleaning the surface of the substrate: Si / SiO2 / Pt was used as the substrate, which was sequentially cleaned in acetone, alcohol, and deionized water for 15 min under ultrasonic wave to remove organic matter and dust on the surface, and finally dried with nitrogen.

[0048] Step S3: spin coating: the GaMn precursor solution obtained in step S1 was spin coated onto the substrate cleaned in step S2 to obtain a preformed film. The spin coating was performed once, and the rotation speed of the spin coater was set to 3000 r / min, and the spin coating time was 30 s.

[0049] Step S4: heat treatment: the spin-coated film obtained in step S3 was heat treated at 480-580°C in an air atmosphere for 1 h.

[0050] The surface of the prepared film was analyzed using AFM, and the AFM image is shown in Figure 1 The film surface was flat, and the surface roughness was less than 1 nm, which was beneficial to device manufacturing. The crystal structure of the prepared film was tested by HRTEM, and the HRTEM image is shown in Figure 2 The HRTEM results showed the disordered atomic arrangement in the film, which confirmed the amorphous nature of the film.

[0051] Step S5: preparation of the top electrode: Pt electrode was grown on the surface of the Mn-doped amorphous gallium oxide film covered with a previously prepared metal mask by electron beam evaporation. In this embodiment, the Pt electrode was circular, and the electrode diameter of the Pt electrode was 100 microns, and the electrode thickness was 200 nm. As shown in Figure 3 , Figure 3 is a schematic diagram of the Pt / a-GMO / Pt resistive random access memory structure.

[0052] The current-voltage characteristics of the Pt / a-GMO / Pt resistive random access memory prepared in Example 1 were tested, and the results are shown in Figure 4As shown, the Pt / a-GMO / Pt device exhibits typical bipolar resistive switching behavior (BRS). During bias applications, a settling process can be observed at 2.6V, triggering a transition from a high-resistance state (HRS or R). OFF ) to low resistance state (LRS or R ON The device can maintain the LRS scan from 3.5V to 0V. Subsequently, when we reverse the scan voltage to reset the voltage, a reset switch is observed. Figure 5 As shown, Figure 5 The durability of the Pt / a-GMO / Pt resistive switching memory (RSM) was demonstrated after 150 cycles. The Pt / a-GMO / Pt RSM showed almost no degradation after 150 cycles, ensuring high repeatability and reliability of switching between HRS and LRS. To verify the memory retention rate of the fabricated device, retention rate testing was performed. Figure 6 As shown, the Pt / a-GMO / Pt device operates at up to 10 3 Maintain good performance within a certain timeframe.

[0053] The inventors defined the resistivity state of the prepared Mn-doped amorphous gallium oxide thin film as the initial state. The hysteresis loops of the Mn-doped amorphous gallium oxide thin film in the three resistivity states are as follows: Figure 7 As shown, different saturation magnetization (Ms) and coercive field (Hc) were observed under different resistance states. For the Pt / a-GMO / Pt device at LRS, the Ms and Hc values ​​were 23.1 emu / cm. 3 And 47.1 Oe. When switching back to HRS, the Ms and Hc values ​​of the memory cells decreased to 18.4 emu / cm. 3 And 35.2 Oe. Therefore, the magnetization of the Pt / a-GMO / Pt device varies with the resistance state, indicating a significant magnetoelectric effect. It is worth noting that R... OFF / R ON Storage windows up to 10 3 This makes it easier for the peripheral circuitry to distinguish and store information.

[0054] Example 2

[0055] This embodiment provides a resistive switching memory based on Mn-doped gallium oxide, prepared by the method of Example 1. The resistive switching memory includes a substrate, an Mn-doped amorphous gallium oxide thin film, and a top electrode. The substrate is a Si / SiO2 / Pt substrate, the Mn-doped amorphous gallium oxide thin film is disposed above the substrate, and the top electrode is disposed above the Mn-doped amorphous gallium oxide thin film.

[0056] Preferably, the electrode diameter of the inert metal electrode is 50-300 nm, the shape of the inert metal electrode is circular or square, and the thickness of the inert metal electrode is 50-1000 nm.

[0057] The preparation method of the application uses a polymer-assisted deposition method to prepare a Mn-doped amorphous gallium oxide film on a Si / SiO2 / Pt substrate, and then an inert metal top electrode is prepared on the film, thereby preparing a sandwich-structured resistive random access memory (Pt / a-GMO / Pt). Simultaneous modulation of the electric field on the resistance and magnetization is achieved, and a multifunctional memory device with super-high R OFF / R ON ratio resistive switching characteristics and magnetic modulation is prepared, while the preparation cost is reduced and the possibility of large-scale commercial application is increased. Mn-doped gallium oxide films have attracted widespread attention in spintronics and electronic applications, in which the magnetic and electrical properties can be adjusted by the bound magnetic polaron (BMP) established between the oxygen vacancies (VO) and the Mn dopant. Notably, the inventors' previous research shows that amorphous manganese-doped gallium oxide (a-GMO) films have much stronger room-temperature ferromagnetism (RTFM) than crystalline films due to the higher VO content in a-GMO. Interestingly, Mn doping in a-GMO provides a tunable two-level doping system, i.e., Mn 3+ and Mn 2+ ions exist in the form of Mn 3+ ions are neutral dopants, and Mn 2+ is a p-type dopant, and the transition between Mn 3+ ions can be achieved by changing the VO concentration. Based on these facts, a-GMO films have the following advantages in the manufacture of resistive random access memories.(1) The low resistance state (LRS) of a-GMO is lower (at least not higher) than that of undoped crystalline gallium oxide, because a-GMO has abundant VO and the LRS only depends on the VO-induced conductive filament in gallium oxide under applied bias, and the high resistance state (HRS) of a-GMO is higher, because Mn 2+ ions can capture the electrons provided by VO and increase the resistivity, resulting in a higher R OFF / R ON ratio.(2) Mn doping not only affects the RS behavior, but also enables magnetic modulation (MM) through electrical means in the bipolar RS process, because the BMP is closely related to the amount of VO that can be modulated by electrical bias, which is conducive to the encoding of quaternary information.(3) The tunable two-level system of Mn doping provides a tool for in-situ non-destructive detection of RS and MM behavior in gallium oxide, which is new and useful for the basic science and practical application of resistive random access memories or memristors.

[0058] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a resistive random access memory based on Mn-doped gallium oxide, characterized in that, The method comprises the following steps: Step S1: preparing GaMn precursor solution: adding 1-100 parts by mass of Mn precursor solution into 100 parts by mass of Ga precursor solution, and fully stirring to obtain GaMn precursor solution; The preparation method of the Ga precursor solution comprises the following steps: adding 2-15 parts by mass of polyethyleneimine and 2-15 parts by mass of ethylenediaminetetraacetic acid into 100 parts by mass of deionized water, fully stirring until clear to obtain a polymer aqueous solution, then adding 1-10 parts by mass of soluble gallium salt into the polymer aqueous solution, fully stirring until uniform, and then ultrafiltrating molecules with a molecular weight less than 10,000 g / mol and concentrating to obtain the Ga precursor solution; The preparation method of the Mn precursor solution comprises the following steps: adding 2-15 parts by mass of polyethyleneimine and 2-15 parts by mass of ethylenediaminetetraacetic acid into 100 parts by mass of deionized water, fully stirring until clear to obtain a polymer aqueous solution, then adding 1-10 parts by mass of soluble manganese salt into the polymer aqueous solution, fully stirring until uniform, and then ultrafiltrating molecules with a molecular weight less than 10,000 g / mol and concentrating to obtain the Mn precursor solution; Step S2: cleaning the surface of the substrate: taking Si / SiO2 / Pt as the substrate, and cleaning the substrate in acetone, alcohol and deionized water by ultrasonic wave for 10-15 min, and finally blowing dry with nitrogen; Step S3: spin coating: spin coating the GaMn precursor solution obtained in step S1 onto the substrate cleaned in step S2 to obtain a pre-prepared film; Step S4: heat treatment: placing the pre-prepared film obtained in step S3 in an oxidizing atmosphere at a temperature of 480-580 ℃ to perform heat treatment, and obtaining an amorphous gallium oxide film doped with Mn; Step S5: preparing a top electrode: growing an inert metal electrode on the surface of the amorphous gallium oxide film doped with Mn covered with a metal mask by electron beam evaporation to prepare a sandwich-structured resistive random access memory.

2. The production method according to claim 1, characterized by, In step S2, the cleaning step of the substrate comprises the following steps: sequentially cleaning in acetone, alcohol and deionized water by ultrasonic wave, and finally blowing dry with nitrogen.

3. The preparation method according to claim 1, characterized in that, In step S3, the spin coating step further comprises the following steps: adjusting the rotation speed and the number of spin coating to adjust the thickness of the prepared film.

4. The production method according to claim 3, characterized by, In the multiple spin coating process, the pre-prepared film is prepared by repeatedly performing step S3 and then performing step S4, or by alternately performing step S3 and step S4.

5. The preparation method according to claim 1, characterized in that, In step S4, the oxidizing atmosphere contains oxygen, and the oxygen content is 10%-100%.

6. The method of claim 1, wherein, In step S5, the inert metal electrode grown on the surface of the amorphous gallium oxide film doped with Mn is an Au or Pt electrode.

7. The preparation method according to claim 6, characterized in that, The electrode diameter of the inert metal electrode is 50-300 nm, the shape of the inert metal electrode is circular or square, and the thickness of the inert metal electrode is 50-1000 nm.

8. A resistive random access memory based on Mn-doped gallium oxide, characterized in that, The resistive random access memory is prepared by the preparation method in any one of the preceding claims 1 to 7, and the resistive random access memory comprises a substrate layer, a Mn-doped amorphous gallium oxide thin film layer and a top electrode, wherein the substrate layer is a Si / SiO2 / Pt substrate, the Mn-doped amorphous gallium oxide thin film layer is arranged above the substrate layer, and the top electrode is arranged above the Mn-doped amorphous gallium oxide thin film layer.

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