A non-volatile ZnO thin film memristor and a preparation method thereof

Abstract

The application belongs to the technical field of microelectronic devices, and particularly relates to a non-volatile ZnO thin film memristor and a preparation method thereof. The device structure comprises: a ZnO thin film intermediate resistive layer prepared by a sol-gel method, FTO as a device bottom electrode, and an electrode layer deposited by a magnetron sputtering film technology to form an upper electrode of the device. The self rectification characteristic of the device can well solve the leakage current problem in a three-dimensional array, and also avoids problems such as high cost, complex structure and inability to realize miniaturization caused by additional rectifier devices of the device, and provides a simple and efficient solution for the realization of high-density multi-value storage of the memristor. The ZnO thin film memristor adopts a W / ZnO / FTO device structure, and through ordered regulation of the limited current of the device, controllable modulation of non-volatile self-rectification multi-value storage of the device is realized, and the ZnO thin film memristor has important development prospects in the application of the next generation of non-volatile high-density memory.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microelectronic devices, and particularly relates to a nonvolatile ZnO thin film memristor and a preparation method thereof. BACKGROUND

[0002] Memristor is considered as one of the powerful competitors of the next generation of nonvolatile storage due to its simple structure, low cost, high speed, low power consumption and high-density multi-value storage. ZnO, as an important wide-bandgap oxide resistive switching medium material, has a band gap of about 3.37 eV at room temperature, and is known as the third generation semiconductor material together with GaN and SiC. ZnO has a series of advantages such as high temperature resistance, simple preparation process and small toxicity, and can be widely used in space technology, nano-optoelectronic technology and semiconductor information storage field. However, how to realize the controllable design of low-cost, high-density self-rectifying multi-value storage of ZnO memristor is still a problem to be solved at present.

[0003] Li Yi et al. of Huazhong University of Science and Technology disclosed "a self-rectifying memristor array and its preparation method and application", with the authorization announcement number CN 114188477 A. The first layer of electrode is photoetched by photoetching mask method, and then the first electrode layer and the second electrode layer are prepared by using methods such as magnetron sputtering, chemical vapor deposition, electron beam evaporation, pulsed laser deposition or atomic layer deposition. The material of the first electrode layer is one or more of a metal element and a conductive metal compound with a work function less than or equal to 4.5 eV. The material of the second electrode layer is one or more of a metal element, a Si element, a doped Si metal element and a conductive metal compound with a work function greater than 4.5 eV. The preparation process of the device is relatively complex and high in cost, which is not conducive to the commercial application of the device. The resistive switching of the device is relatively low, unstable and low in reliability. The device does not realize the controllable modulation of multi-value storage.

[0004] Based on the above analysis, a nonvolatile ZnO thin film memristor with simple preparation method, high preparation efficiency, and controllable design of high stability, high reliability and self-rectifying multi-value storage is urgently needed in the industry. SUMMARY

[0005] In view of the shortcomings of the prior art, the purpose of the application is to provide a simple and efficient preparation technology of nonvolatile ZnO thin film memristor, and realize the controllable design of high stability, high reliability and self-rectifying multi-value storage of the device.

[0006] The application is realized by the following technical means:

[0007] A non-volatile ZnO thin film memristor, the device structure comprises: a ZnO thin film intermediate resistive layer prepared by sol-gel method, FTO as the bottom electrode of the device, and an electrode layer deposited by magnetron sputtering film technology to form the upper electrode of the device.

[0008] A preparation method of a non-volatile ZnO thin film memristor, the steps are as follows:

[0009] (1) Preparation of ZnO precursor solution: zinc acetate dihydrate as zinc source, ethylene glycol methyl ether as solvent, ethanolamine as stabilizer, mix them in a certain proportion and concentration, then magnetically stir to obtain ZnO precursor solution.

[0010] (2) Use a pipette to take an appropriate amount of ZnO precursor solution and drop it on a FTO glass sheet with a size of 1cm×2cm, evenly glue to form a uniform ZnO precursor film, dry the spin-coated film sample for 5-10min, repeat the above glueing step until the film thickness reaches the required sample.

[0011] Further, the glueing step is completed in two steps, the first step is to evenly glue at a speed of 1000-1500r / min for 5-15s; the second step is to evenly glue at a speed of 2000-3500r / min for 10-35s.

[0012] (3) After drying the sample of step (2), put it into a muffle furnace for rapid annealing, take it out after natural cooling to room temperature, and get a uniform ZnO thin film sample.

[0013] Further, the annealing temperature of the muffle furnace is 500-800℃, and the time is 5-15min.

[0014] (4) According to the design requirements, the sample preparation process of steps (1)-(3) can also be repeated several times to design samples with different thickness or multi-layer ZnO thin film structure requirements.

[0015] (5) Use metal mask magnetron sputtering film technology to sputter deposit a certain thickness and morphology of the upper electrode on the ZnO thin film sample prepared in step (4) to realize the design of ZnO thin film memristor.

[0016] Further, the upper electrode of the device can be a metal electrode or a non-metal electrode.

[0017] Use B2901A semiconductor device analyzer to test the electrical properties of ZnO thin film memristor. By orderly controlling the limiting current of the device, the controllable modulation of non-volatile self-rectifying multi-value storage of the device is realized. In addition, the multi-value storage control of the device can also be controlled by adjusting the external bias voltage, light field, magnetic field and other physical field excitation to realize the controllable modulation of multi-value storage.

[0018] The application has the advantages that:

[0019] 1. The application provides a non-volatile ZnO thin film memristor and a preparation and self-rectifying multi-value storage regulation method thereof, which can reduce the interference of leakage current in a cross-over three-dimensional array, does not need to be additionally integrated with a rectifier device, can better achieve the purposes of low cost and miniaturization, and is convenient for commercial application.

[0020] 2. The application provides a simple, inexpensive and efficient glue uniformizing preparation process, realizes controllable preparation of a ZnO nanometer thin film, and provides a simple and efficient implementation means for development and application of related materials.

[0021] 3. The ZnO thin film memristor designed in the application has high stability, non-volatile self-rectifying multi-value resistance change storage characteristics, and has important development prospects in the application of the next generation of non-volatile high-density storage. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 1 is a structure schematic diagram of the device designed in the embodiment 1 of the application;

[0023] Figure 2 Fig. 2 is a surface morphology FESEM diagram of the ZnO thin film sample prepared in the embodiment 1 of the application;

[0024] Figure 3 Fig. 3 is a cross-section morphology FESEM diagram of the ZnO thin film sample prepared in the embodiment 1 of the application;

[0025] Figure 4 Fig. 4 is an XPS diagram of the surface Zn2p of the ZnO thin film sample prepared in the embodiment 1 of the application;

[0026] Figure 5 Fig. 5 is an XPS diagram of the surface O1s of the ZnO thin film sample prepared in the embodiment 1 of the application;

[0027] Figure 6 Fig. 6 is a semi-logarithmic I-V curve diagram of the device in the embodiment 2 of the application under 50 times of cyclic voltage scanning;

[0028] Figure 7 Fig. 7 is a semi-logarithmic I-V curve diagram of the device in the embodiment 2 of the application under current limiting regulation. DETAILED DESCRIPTION

[0029] The application will be described in detail below with reference to the drawings.

[0030] Embodiment 1

[0031] A non-volatile ZnO thin film memristor

[0032] The structure is shown in Figure 1 The upper electrode of the device is a metal W electrode (thickness of about 50 nm), the middle resistive layer is a ZnO film (thickness of about 100 nm), and the bottom electrode is an FTO conductive glass substrate.

[0033] The specific steps for preparing the nonvolatile ZnO film memristor are as follows:

[0034] (1) Preparation of ZnO precursor solution: zinc acetate dihydrate and ethylene glycol methyl ether are mixed to prepare a 0.075 mol / L solution, and then 600 μL of ethanolamine is added as a stabilizer under magnetic stirring. The three are placed in a magnetic stirrer for stirring until a transparent yellow ZnO precursor solution is obtained.

[0035] (2) 100 μL of the precursor solution in step (1) is taken by a pipette and dropped on an FTO glass sheet with a size of 1 cm x 2 cm to form a uniform ZnO precursor film. The spin-coated film sample is dried for 10 min. The spin-coating is repeated 5 times, and each time is divided into two steps. The first step is spin-coating at a speed of 1000 r / min for 10 s, and the second step is spin-coating at a speed of 3500 r / min for 30 s.

[0036] (3) After the spin-coating operation is completed, the sample in step (2) is placed in an 800℃ muffle furnace for rapid annealing for 10 min. After it is naturally cooled to room temperature, it is washed with deionized water, naturally dried, and a ZnO film sample with a uniform surface is obtained. The surface and cross-sectional morphology of the ZnO film sample are shown in Figure 2 and Figure 3 .

[0037] As shown in Figure 2 and Figure 3 , the surface of the ZnO film sample is composed of fine particles with a diameter of 30 nm, and the thickness of the ZnO film is about 100 nm.

[0038] As shown in Figure 4 , the XPS diagram of Zn 2p on the surface of the ZnO film sample can be found that the two spin-orbit coupling energy levels of Zn 2p 3 / 2 and Zn 2p 1 / 2 are symmetrical Gaussian-Lorentz peaks, and the binding energy of Zn 2p 1 / 2 is 1022 eV, which is close to the Zn 2p 1 / 2 binding energy (1021.75 eV) of the hexagonal wurtzite bulk structure ZnO, indicating that the Zn element in the prepared ZnO film sample mainly exists in the form of Zn 2+ .

[0039] As shown inFigure 5 The XPS diagram of O1s of the ZnO thin film sample is shown. It can be found that two peaks appear from left to right, which are 530.1 eV and 531.8 eV respectively, corresponding to the lattice oxygen and amorphous oxygen (mainly oxygen vacancies) in the sample. The existence of oxygen vacancies will directly affect the resistive switching behavior of the ZnO thin film memristor.

[0040] (4) A certain pattern of metal W is sputtered and deposited on the surface of the ZnO thin film prepared in step (3) as the upper electrode of the device by using a metal mask plate magnetron sputtering film forming technology, the thickness is 80 nm, and the diameter is 5 μm, so as to realize the design of the ZnO thin film memristor.

[0041] Example 2

[0042] A non-volatile ZnO thin film memristor

[0043] The specific steps for preparing the non-volatile ZnO thin film memristor are as follows:

[0044] (1) Preparation of ZnO precursor solution. Zinc acetate dihydrate and ethylene glycol methyl ether are mixed to prepare a solution with a concentration of 0.075 mol / L, and then 600 μL of ethanolamine is added as a stabilizer under magnetic stirring. The three are mixed and placed in a magnetic stirrer for stirring until a transparent yellow ZnO precursor solution is obtained.

[0045] (2) 100 μL of the precursor solution in step (1) is taken by a pipette and dropped on a FTO glass sheet with a size of 1 cm x 2 cm to form a uniform ZnO precursor film. The spin-coated film sample is dried for 7.5 min. Repeat the spin coating 5 times, each time divided into two steps. The first step is spin coating at a speed of 1200 r / min for 15 s; the second step is spin coating at a speed of 2500 r / min for 35 s.

[0046] (3) After the spin coating operation is completed, the sample in step (2) is placed in a 700℃ muffle furnace for rapid annealing for 15 min. After it is naturally cooled to room temperature, it is taken out, washed with deionized water, and naturally dried to obtain a ZnO thin film sample with a uniform surface and a thickness of about 80 nm.

[0047] (4) A certain pattern of metal W is sputtered and deposited on the surface of the ZnO thin film prepared in step (3) as the upper electrode of the device by using a metal mask plate magnetron sputtering film forming technology, the thickness is 80 nm, and the diameter is 5 μm, so as to realize the design of the ZnO thin film memristor.

[0048] Example 3

[0049] A non-volatile ZnO thin film memristor

[0050] The preparation of the non-volatile ZnO thin film memristor is specifically as follows:

[0051] (1) Preparation of ZnO precursor solution. Zinc acetate dihydrate is mixed with ethylene glycol methyl ether to prepare a 0.075 mol / L solution, and then 600 μL of ethanolamine is added as a stabilizer under magnetic stirring. The three are mixed and placed in a magnetic stirrer for stirring until a transparent yellow ZnO precursor solution is obtained.

[0052] (2) 100 μL of the precursor solution in step (1) is taken by a pipette and dropped on a FTO glass sheet with a size of 1 cm x 2 cm to form a uniform ZnO precursor film. The spin-coated film sample is dried for 5 min. The spin-coating is repeated 5 times, and each time is divided into two steps. The first step is spin-coating at a speed of 1500 r / min for 5 s, and the second step is spin-coating at a speed of 2000 r / min for 10 s.

[0053] (3) After the spin-coating operation is completed, the sample in step (2) is placed in a 500°C muffle furnace for rapid annealing for 5 min. After it is naturally cooled to room temperature, it is taken out, washed with deionized water, and naturally dried to obtain a ZnO thin film sample with a uniform surface and a thickness of about 50 nm.

[0054] (4) A metal mask magnetron sputtering film technology is used to sputter deposit a certain pattern of metal W on the surface of the ZnO thin film prepared in step (3) as the upper electrode of the device, with a thickness of 80 nm and a diameter of 5 μm, to realize the design of the ZnO thin film memristor.

[0055] Test Example 1

[0056] A self-rectifying multi-value storage control method for a non-volatile ZnO thin film memristor

[0057] The self-rectifying multi-value storage control method for a non-volatile ZnO thin film memristor of the present embodiment. Under the optimized device preparation process conditions, the upper electrode of the device is a metal W electrode (with a thickness of about 50 nm), the middle resistive layer is a ZnO thin film (with a thickness of about 100 nm), and the bottom electrode is an FTO conductive glass substrate. In terms of device testing and control, the limiting current of the ordered control device is used to realize the controllable modulation of the self-rectifying multi-value storage of the device.

[0058] The specific steps of the self-rectifying multi-value storage control of the device are as follows:

[0059] 1. First, since the device does not need to be electrically activated, the process is as follows: Figure 1As shown, in the scanning voltage range of-3.5~2.5V, the bias voltage is directly applied to the W top electrode of the device, and the FTO bottom electrode of the device is grounded, and the resistance switching characteristics of the device are tested and controlled.

[0060] 2. Secondly, in the performance test of the device. As shown, Figure 6 As shown, under 50 cycles of voltage scanning (limited current is 100mA), the device shows high stability, non-volatile self-rectifying resistance switching memory characteristics. The set voltage and reset voltage of the device can be stably maintained at about 0.2V and-1V, respectively. In addition, the resistance switching ratio of the device is close to two orders of magnitude at-0.1V, showing good resistance switching memory characteristics.

[0061] 3. Finally, in the controllable modulation of self-rectifying multi-value memory of the device. As shown, Figure 7 As shown, by orderly controlling the limited current (10~100mA) of the device, the controllable modulation of self-rectifying multi-value memory of the device is realized.

[0062] The above embodiments are only the device design and multi-value memory modulation technology under the optimization of process conditions and control methods. Any structure design, preparation process of the ZnO thin film memristor resistance switching layer, preparation of the top electrode or bottom electrode, and equivalent replacement design of the device electrode, all belong to the legal protection scope of this patent. Including but not limited to:

[0063] ①For the bottom electrode of the device, in addition to using the FTO bottom electrode, other bottom electrodes suitable for uniform coating method can also be used for replacement.

[0064] ②For the ZnO thin film resistance switching layer of the device, in addition to using sol-gel method, a series of convenient operation technologies such as chemical vapor deposition, plasma enhanced atomic layer deposition, electron beam evaporation deposition technology, magnetron sputtering deposition, and hydrothermal method can also be used for preparation. In addition to using single-layer ZnO thin film, the resistance switching layer material with heterojunction device structure can also be prepared.

[0065] ③For the top electrode of the device, in addition to using magnetron sputtering deposition, other methods can also be used to prepare the top electrode, such as molecular beam epitaxy deposition, sol-gel method, thermal evaporation, chemical vapor deposition, etc. In addition, in addition to using W top electrode, according to the design requirements of the device, other metal electrodes or non-metal electrodes can also be selected.

Claims

1.A non-volatile ZnO thin film memristor, comprising: a resistive switching layer, a bottom electrode and an upper electrode; the resistive switching layer is a ZnO thin film intermediate resistive switching layer with a thickness of 50-100 nm prepared by a sol-gel method; the bottom electrode is FTO; the upper electrode is selected from tungsten; the upper electrode is an electrode layer deposited by magnetron sputtering coating technology; wherein: the non-volatile ZnO thin film memristor is prepared by the following method: (1) 1.5 mM zinc acetate dihydrate is added to 20 mL ethylene glycol methyl ether to prepare a 0.075 mol / L solution, and then 600 μL of ethanolamine is added as a stabilizer, and the ZnO precursor solution is obtained by magnetic stirring; (2) the ZnO precursor solution is drawn onto the FTO glass sheet, and a uniform ZnO precursor film is formed by uniform coating, the spin-coated film sample is dried for 5-10 min, and the above uniform coating step is repeated until the film thickness reaches the required sample; (3) the sample in step (2) is dried and then placed in a muffle furnace for rapid annealing, the annealing temperature is 500-800℃, the time is 5-15 min, and after natural cooling to room temperature, the surface uniform ZnO thin film sample is obtained; (4) the upper electrode is sputtered and deposited on the surface of the ZnO thin film sample prepared in step (3) by metal mask magnetron sputtering coating technology, and a non-volatile ZnO thin film memristor is obtained. 2.The non-volatile ZnO thin film memristor of claim 1, wherein: the uniform coating in step (2) is completed in two steps. 3.The non-volatile ZnO thin film memristor of claim 1, wherein: the first step of uniform coating has a speed of 1000-1500 r / min and a time of 5-15 s; the second step of uniform coating has a speed of 2000-3500 r / min and a time of 10-35 s.

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