Zinc gallate resistive random access memory and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor materials, and discloses a zinc gallate resistive random access memory and a preparation method thereof. According to the zinc gallate resistive random access memory, the zinc gallate thin film is prepared on the FTO bottom electrode substrate through a spin-coating method, then the active metal top electrode is prepared on the zinc gallate thin film, and therefore the zinc gallate resistive random access memory of a sandwich structure is prepared and obtained. The switching between a high resistance state (HRS) and a low resistance state (LRS) has excellent stability; the low resistance of different electrodes of the zinc gallate resistive random access memory prepared by the method is concentrated at about 102 ohms, and the high resistance is concentrated at about 103-104 ohms, so that good in-chip consistency is embodied; in addition, the preparation method disclosed by the invention is low in preparation cost and short in preparation period, so that large-scale application becomes possible.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and in particular to a zinc gallate resistive random access memory and a preparation method thereof. Background Art

[0002] Resistive random access memory (RRAM, also known as memristor) is the fourth basic circuit element besides resistors, capacitors, and inductors. Compared with several traditional memories, RRAM has the characteristics of high speed, low power consumption, high integration, and both information storage and computing functions. It is expected to fundamentally subvert the traditional von Neumann computing architecture and the entire computer system foundation. Resistive random access memory is usually a metal / dielectric layer / metal sandwich structure, with the metal layer as the upper and lower electrodes and the dielectric layer as the resistive material.

[0003] Binary oxides such as gallium oxide and zinc oxide are widely used in dielectric layers of resistive random access memories, showing good bipolar resistive switching characteristics and chemical stability. Zinc gallate, as a derivative semiconductor of gallium oxide and zinc oxide, has many similarities in semiconductor properties with gallium oxide and zinc oxide, such as being a direct bandgap semiconductor with a large bandgap width, and should have the same excellent resistive switching characteristics. However, at present, there are few studies on the use of zinc gallate in the dielectric layer of resistive random access memories. Therefore, in order to study the resistive switching characteristics of zinc gallate similar to those of gallium oxide and zinc oxide, the development of zinc gallate resistive random access memories and their preparation methods have become technical problems that need to be solved urgently by those skilled in the art. Summary of the invention

[0004] The purpose of the present invention is to provide a zinc gallate resistive random access memory and a preparation method thereof, so as to alleviate the current predicament of lack of zinc gallate in resistive random access memory on the market and improve the stability of the zinc gallate resistive random access memory.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] A zinc gallate resistive memory, which is composed of a stacked top electrode, a resistive switching layer and a bottom electrode substrate;

[0008] Wherein, the resistive switching layer is a zinc gallate film.

[0009] Further, the top electrode is an active metal electrode;

[0010] Preferably, the top electrode is a Cu electrode.

[0011] Furthermore, the bottom electrode substrate is a FTO substrate.

[0012] The second technical solution of the present invention:

[0013] The above-mentioned method for preparing the zinc gallate resistive random access memory comprises the following steps:

[0014] 1) Preparation of ZnGa2O4 precursor solution:

[0015] Mixing zinc acetate hydrate and gallium nitrate hydrate, and dissolving them in a quantitative amount of ethylene glycol methyl ether solvent to obtain a colorless and transparent ZnGa2O4 precursor solution;

[0016] 2) Preparation of ZnGa2O4 prefabricated film:

[0017] Spin-coating the ZnGa2O4 precursor solution obtained in step 1) onto the surface of the FTO substrate, and then heat-treating the FTO substrate on which the ZnGa2O4 precursor solution is spin-coated to form a ZnGa2O4 pre-film;

[0018] 3) Preparation of ZnGa2O4 thin film:

[0019] The ZnGa2O4 prefabricated film obtained in step 2) is placed in a tube furnace for annealing to obtain a ZnGa2O4 thin film;

[0020] 4) Preparation of top electrode:

[0021] An active metal electrode is grown on the surface of a ZnGa2O4 film covered with a metal mask by using a gold evaporator to obtain the zinc gallate resistive random access memory.

[0022] Furthermore, in step 1), the zinc acetate hydrate and the gallium nitrate hydrate are mixed in an atomic molar ratio of Zn:Ga=1:2.

[0023] Furthermore, in step 1), the concentration of the precursor solution is 0.1 mol / L.

[0024] Furthermore, before preparing the ZnGa2O4 pre-film in step 2), the FTO substrate needs to be pre-treated.

[0025] Furthermore, the pre-treatment specifically includes: performing ultrasonic cleaning and ozone treatment on the FTO substrate in sequence.

[0026] Furthermore, the ultrasonic cleaning is specifically as follows: placing the FTO substrate in deionized water containing detergent, deionized water, acetone and ethanol in sequence, ultrasonic cleaning for 30 minutes, and then placing the FTO substrate in a drying oven at 60° C. for 6 hours.

[0027] Furthermore, the ozone treatment is specifically as follows: placing the FTO substrate after ultrasonic cleaning in a UV ozone cleaning machine for ozone treatment for 2 hours;

[0028] Furthermore, the power of the lamp group of the UV ultraviolet ozone cleaning machine is 240w, and the distance between the base and the lamp group is 20mm.

[0029] Furthermore, in step 2), the spin coating is performed using a spin coater, and the parameters of the spin coater are: rotation speed 3000 r / min, rotation acceleration 1000 r / min, and spin coating time 30 s.

[0030] Furthermore, in step 2), the heating treatment is specifically: heating at 150° C. for 10 minutes.

[0031] Furthermore, in step 2), the thickness of the ZnGa2O4 prefabricated film is 260 nm.

[0032] Furthermore, in step 3), the annealing treatment is specifically: annealing treatment at 500° C. for 2 hours.

[0033] Furthermore, in step 4), the diameter of the active metal electrode is 50-500 nm, and the shape is circular or square.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The invention adopts a spin coating method to prepare a zinc gallate film on a FTO bottom electrode substrate, and then prepares an active metal top electrode on the zinc gallate film, thereby preparing a sandwich structure zinc gallate resistive random access memory. The zinc gallate resistive random access memory prepared by the invention has almost no degradation after 200 cycles, and has excellent stability in switching between a high resistance state (HRS) and a low resistance state (LRS); and the low resistance of different electrodes of the zinc gallate resistive random access memory prepared by the invention is concentrated in 10 2 Ω, high resistance is concentrated around 10 3 ~10 4 Ω, which reflects good on-chip consistency; the dielectric layer in the resistive random access memory prepared by the present invention is zinc gallate, which is a direct bandgap semiconductor with excellent thermal stability, chemical stability and wide bandgap. Compared with binary compounds, in addition to common defects such as vacancies and gaps, ZnGa2O4 has unique Zn 2+ and Ga 3+ The double cation structure easily forms a cation substitution position, which constitutes an anti-site defect. Therefore, ZnGa2O4 can achieve Zn by controlling the growth conditions. 2+ and Ga 3+ The position and proportion can be regulated, and then the electrical properties can be regulated, so that it has great potential in memory applications; in addition, the preparation method of the present invention has low preparation cost and short preparation cycle, making its large-scale application possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0037] Figure 1 This is the XRD pattern of the ZnGa2O4 thin film prepared in Example 1 of the present invention;

[0038] Figure 2 The diffuse reflection spectrum and bandgap width diagram of the ZnGa2O4 film prepared in Example 1 of the present invention;

[0039] Figure 3 This is a surface SEM image of the ZnGa2O4 thin film prepared in Example 1 of the present invention;

[0040] Figure 4 This is a cross-sectional SEM image of the ZnGa2O4 thin film prepared in Example 1 of the present invention;

[0041] Figure 5 This is a schematic diagram of the structure of the zinc gallate resistive random access memory prepared in Example 1 of the present invention;

[0042] Figure 6 A typical bipolar resistive switching behavior curve of the zinc gallate resistive memory prepared in Example 1 of the present invention;

[0043] Figure 7 The endurance test result diagram of the zinc gallate resistive random access memory prepared in Example 1 of the present invention is shown in Figure 1, wherein A is a graph showing a cycle test of the IV curve of the resistive random access memory, and B is a graph showing the distribution of HRS and LRS;

[0044] Figure 8 The resistance state distribution diagram of the zinc gallate resistive random access memory prepared in Example 1 of the present invention at 6 points. DETAILED DESCRIPTION

[0045] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0046] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0047] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0048] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0049] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0050] In the following examples, the raw materials are all commercially available.

[0051] In the following embodiment, a method for preparing a zinc gallate resistive random access memory includes the following steps:

[0052] 1) Preparation of ZnGa2O4 precursor solution:

[0053] According to the atomic molar ratio of Zn:Ga=1:2, zinc acetate hydrate and gallium nitrate hydrate are mixed and dissolved in a certain amount of ethylene glycol methyl ether solvent to obtain a colorless and transparent precursor solution with a concentration of 0.1 mol / L;

[0054] 2) Pretreatment of FTO substrate:

[0055] The FTO substrate was placed in deionized water containing detergent, deionized water, acetone and ethanol in turn, and ultrasonically cleaned for 30 min. The FTO substrate was then placed in a drying oven at 60 °C and dried for 6 h.

[0056] The FTO substrate after ultrasonic cleaning was placed in a UV ozone cleaning machine for ozone treatment for 2 hours;

[0057] Among them, the lamp group power of the UV ultraviolet ozone cleaning machine is 240w, and the distance between the base and the lamp group is 20mm;

[0058] 3) Preparation of ZnGa2O4 prefabricated film:

[0059] The ZnGa2O4 precursor solution obtained in step 1) is spin-coated onto the surface of the FTO substrate pretreated in step 2), and then the FTO substrate spin-coated with the ZnGa2O4 precursor solution is placed on a heating table and heated at 150° C. for 10 min to form a ZnGa2O4 pre-film with a thickness of 260 nm;

[0060] The spin coating is performed by a spin coater, and the parameters of the spin coater are: rotation speed 3000r / min, rotation acceleration 1000r / min, and spin coating time 30s;

[0061] Those skilled in the art can achieve the ZnGa2O4 pre-film thickness defined in the present invention by adjusting the number of spin coatings according to conventional technical means;

[0062] 4) Preparation of ZnGa2O4 thin film:

[0063] The ZnGa2O4 prefabricated film obtained in step 3) is placed in a tube furnace and annealed at 500° C. for 2 h to obtain a ZnGa2O4 thin film;

[0064] 5) Preparation of top electrode:

[0065] An active metal electrode with a diameter of 50 to 500 nm and a circular or square shape is grown on the surface of a ZnGa2O4 film covered with a metal mask by using a gold evaporator to obtain the zinc gallate resistive random access memory.

[0066] Example 1

[0067] A method for preparing zinc gallate resistive random access memory

[0068] 1) Preparation of ZnGa2O4 precursor solution:

[0069] According to the atomic molar ratio of Zn:Ga=1:2, zinc acetate hydrate and gallium nitrate hydrate are mixed and dissolved in a certain amount of ethylene glycol methyl ether solvent to obtain a colorless and transparent precursor solution with a concentration of 0.1 mol / L;

[0070] 2) Pretreatment of FTO substrate:

[0071] The FTO substrate was placed in deionized water containing detergent, deionized water, acetone and ethanol in turn, and ultrasonically cleaned for 30 min. The FTO substrate was then placed in a drying oven at 60 °C and dried for 6 h.

[0072] The FTO substrate after ultrasonic cleaning was placed in a UV ozone cleaning machine for ozone treatment for 2 hours;

[0073] Among them, the lamp group power of the UV ultraviolet ozone cleaning machine is 240w, and the distance between the base and the lamp group is 20mm;

[0074] 3) Preparation of ZnGa2O4 prefabricated film:

[0075] Spin-coat the ZnGa2O4 precursor solution obtained in step 1) onto the surface of the FTO substrate pretreated in step 2), repeat the spin-coating 4 times, then place the FTO substrate spin-coated with the ZnGa2O4 precursor solution on a heating table, and heat at 150° C. for 10 min to form a ZnGa2O4 pre-film with a thickness of 260 nm;

[0076] The spin coating is performed by a spin coater, and the parameters of the spin coater are: rotation speed 3000r / min, rotation acceleration 1000r / min, and spin coating time 30s;

[0077] 4) Preparation of ZnGa2O4 thin film:

[0078] The ZnGa2O4 prefabricated film obtained in step 3) is placed in a tube furnace and annealed at 500° C. for 2 h to obtain a ZnGa2O4 thin film;

[0079] 5) Preparation of top electrode:

[0080] A Cu electrode with a diameter of 250 nm and a circular shape is grown on the surface of a ZnGa2O4 film covered with a metal mask by using a gold evaporator to obtain the zinc gallate resistive random access memory.

[0081] The ZnGa2O4 film prepared in step 4) of Example 1 was subjected to X-ray diffraction analysis. The XRD pattern of the ZnGa2O4 film is as follows: Figure 1 As shown;

[0082] Depend on Figure 1 It can be seen that the diffraction peak of the ZnGa2O4 film prepared by the present invention is consistent with the ZnGa2O4 standard card (PDF: 38-1240), and is a wide bandgap material.

[0083] The ZnGa2O4 film prepared in step 4) of Example 1 was subjected to UV-visible diffuse reflectance analysis. The diffuse reflectance spectrum and bandgap width of the ZnGa2O4 film are shown in the figure below: Figure 2 As shown;

[0084] Depend on Figure 2 It can be seen that the band gap of the ZnGa2O4 film prepared by the present invention is approximately 4.66 eV.

[0085] The surface of the ZnGa2O4 film prepared in step 4) of Example 1 was analyzed by surface scanning electron microscopy. The surface SEM image of the ZnGa2O4 film is as follows: Figure 3 As shown;

[0086] Depend on Figure 3 It can be seen that the surface of the ZnGa2O4 film prepared by the present invention has obvious crystallization, the crystal grain size is at the nanometer level, the ZnGa2O4 film particles are small and have good density, which is conducive to the preparation of subsequent devices.

[0087] The ZnGa2O4 film prepared in step 4) of Example 1 was subjected to cross-sectional scanning electron microscopy analysis. The cross-sectional SEM image of the ZnGa2O4 film is as follows: Figure 4 As shown;

[0088] Depend on Figure 4 It can be seen that the thickness of the FTO bottom electrode substrate is about 320nm, and the thickness of the ZnGa2O4 film is about 260nm.

[0089] The structural schematic diagram of the zinc gallate resistive random access memory prepared in Example 1 is as follows Figure 5 shown.

[0090] The IV curve of the zinc gallate resistive memory prepared in Example 1 is analyzed. The typical bipolar resistive behavior curve of the zinc gallate resistive memory is shown in FIG. Figure 6 As shown;

[0091] Depend on Figure 6 It can be seen that the zinc gallate resistive memory prepared by the present invention shows a typical bipolar resistive switching behavior. As the applied voltage increases, a set process can be seen to occur at 0.8V, which triggers a sudden change from a high resistance state (HRS) to a low resistance state (LRS). The zinc gallate resistive memory can maintain the LRS scanned from 1.6V to 0V. Subsequently, when the voltage is reversely scanned to reset the voltage, a reset switch (Reset) is observed.

[0092] The zinc gallate resistive random access memory prepared in Example 1 was subjected to a durability test in 200 cycles. The test results are as follows: Figure 7 As shown, A is the IV curve cycle test diagram of the resistive memory, and B is the HRS and LRS distribution diagram;

[0093] Depend on Figure 7 It can be seen that the zinc gallate resistive memory prepared by the present invention has almost no degradation after 200 cycles, and the high and low resistance values ​​can still change by more than one order of magnitude, which proves that the switching between high and low resistance states of the zinc gallate resistive memory prepared by the present invention has high repeatability and reliability.

[0094] The uniformity of the zinc gallate resistive random access memory prepared in Example 1 was tested by testing the resistance at 6 points with the same electrode size. The resistance distribution diagrams obtained at the 6 points are as follows: Figure 8 As shown;

[0095] Depend on Figure 8 It can be seen that the low resistance of the zinc gallate resistive memory prepared by the present invention is concentrated in 10 2 Ω, high resistance is concentrated around 10 3 ~10 4 The device exhibits good uniformity.

[0096] 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 above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A zinc gallate resistive random access memory, characterized in that: The zinc gallate resistive memory is composed of a stacked top electrode, a resistive switching layer and a bottom electrode substrate; Wherein, the resistive switching layer is a zinc gallate film.

2. The zinc gallate resistive random access memory according to claim 1, characterized in that: The top electrode is an active metal electrode; the bottom electrode substrate is a FTO substrate.

3. A method for preparing the zinc gallate resistive random access memory according to any one of claims 1 to 2, characterized in that: The following steps are involved: 1) Preparation of ZnGa2O4 precursor solution: Mixing zinc acetate hydrate and gallium nitrate hydrate, and dissolving them in a quantitative amount of ethylene glycol methyl ether solvent to obtain a colorless and transparent ZnGa2O4 precursor solution; 2) Preparation of ZnGa2O4 prefabricated film: Spin-coating the ZnGa2O4 precursor solution obtained in step 1) onto the surface of the FTO substrate, and then heat-treating the FTO substrate on which the ZnGa2O4 precursor solution is spin-coated to form a ZnGa2O4 pre-film; 3) Preparation of ZnGa2O4 thin film: The ZnGa2O4 prefabricated film obtained in step 2) is placed in a tube furnace for annealing to obtain a ZnGa2O4 thin film; 4) Preparation of top electrode: An active metal electrode is grown on the surface of a ZnGa2O4 film covered with a metal mask by using a gold evaporator to obtain the zinc gallate resistive random access memory.

4. The preparation method according to claim 3, characterized in that: In step 1), zinc acetate hydrate and gallium nitrate hydrate are mixed according to an atomic molar ratio of Zn:Ga=1:2; the concentration of the precursor solution is 0.1 mol / L.

5. The preparation method according to claim 3, characterized in that: Before preparing the ZnGa2O4 pre-film in step 2), the FTO substrate needs to be pre-treated.

6. The preparation method according to claim 5, characterized in that: The pre-treatment specifically includes: performing ultrasonic cleaning and ozone treatment on the FTO substrate in sequence.

7. The preparation method according to claim 6, characterized in that: The ultrasonic cleaning is specifically as follows: placing the FTO substrate in deionized water containing detergent, deionized water, acetone and ethanol in turn, ultrasonic cleaning for 30 minutes, and then placing the FTO substrate in a drying oven at 60° C. for 6 hours; the ozone treatment is specifically as follows: placing the FTO substrate after ultrasonic cleaning in a UV ultraviolet ozone cleaning machine for ozone treatment for 2 hours.

8. The preparation method according to claim 3, characterized in that: In step 2), the spin coating is performed using a spin coater, and the parameters of the spin coater are: rotation speed 3000r / min, rotation acceleration 1000r / min, and spin coating time 30s; the heat treatment is specifically: heating at 150°C for 10min; the thickness of the ZnGa2O4 prefabricated film is 260nm.

9. The preparation method according to claim 3, characterized in that: The annealing treatment is specifically: annealing at 500° C. for 2 hours.

10. The preparation method according to claim 3, characterized in that: In step 4), the active metal electrode has a diameter of 50 to 500 nm and a circular or square shape.

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