Manufacturing method of memristor for generating oxygen vacancies by X-ray irradiation

Abstract

The invention discloses a memristor manufacturing method for generating oxygen vacancies by X-ray irradiation. The memristor manufacturing method comprises the following steps: taking a resistive layer; respectively depositing a top surface insulating layer and a bottom surface insulating layer on the top surface and the bottom surface of the resistive layer; etching the top surface insulating layer to form a top surface square hole array, etching the bottom surface insulating layer to form a bottom surface square hole array, respectively forming top electrodes in top surface square holes, and respectively forming bottom electrodes in bottom surface square holes; x-rays are adopted to irradiate the resistive layer, and the needed oxygen vacancy concentration gradient is generated in the preset area of the resistive layer. According to the method, the oxygen vacancy concentration distribution is effectively controlled through X-ray irradiation, and compared with a traditional gas ion implantation method, the method has the advantages of being simple in process, precise in vacancy generation control and low in energy consumption, and is particularly suitable for being applied to a high-radiation environment and a nonvolatile memory requiring high performance.

Description

Technical Field

[0001] The invention belongs to the field of memristor manufacturing, and in particular relates to a memristor manufacturing method which generates oxygen vacancies by X-ray irradiation. Background Art

[0002] Memristors have become a hot topic in the research of next-generation non-volatile memory due to their simple structure, compatibility with CMOS processes, high integration density, low power consumption, and high speed. However, current memristors face problems such as high threshold voltage, poor consistency, and short life, which hinder their commercialization.

[0003] Traditionally, gas ion implantation is used to generate oxygen vacancies in the resistive layer, which play a key role in the formation and breakage of conductive filaments. However, the gas ion implantation method often leads to uneven vacancy distribution, thus affecting the stability of the device. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method for manufacturing a memristor by generating oxygen vacancies by X-ray irradiation, so as to control the switching characteristics of the memristor.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies comprises the following steps:

[0007] S100, obtaining a resistive switching layer, wherein the resistive switching layer is composed of one or more metal compounds;

[0008] S200, depositing a top insulating layer and a bottom insulating layer on the top surface and the bottom surface of the resistive layer respectively;

[0009] S300, etching the top surface insulating layer to form a plurality of top surface square holes, and etching the bottom surface insulating layer to form a plurality of bottom surface square holes; the plurality of top surface square holes form a top surface square hole array, and the plurality of bottom surface square holes form a bottom surface square hole array;

[0010] S400, forming a top electrode in each of the top surface square holes, and forming a bottom electrode in each of the bottom surface square holes;

[0011] S500, irradiating the resistive switching layer with X-rays to generate a required oxygen vacancy concentration gradient in a predetermined region of the resistive switching layer.

[0012] Furthermore, in the step S100, the metal compound of the resistive layer is a monovalent or polyvalent metal compound, and the metal valence is not less than two-thirds of the highest positive valence of the metal.

[0013] Furthermore, the resistive switching layer is a Nb-doped single crystal SrTiO3 substrate, the doping mass fraction is 0.7%, and the crystal orientation is <100> .

[0014] Furthermore, in the step S200, the thickness of the top insulating layer and the bottom insulating layer is 40 nm to 60 nm.

[0015] Furthermore, in the step S300, a negative resist process is used to etch the top insulating layer to form a top square hole array, and to etch the bottom insulating layer to form a bottom square hole array.

[0016] Furthermore, the size of the square holes on the top surface and the square holes on the bottom surface is 80 μm×80 μm.

[0017] Furthermore, the step S400 includes the following sub-steps:

[0018] S410, depositing a top metal layer on the top insulating layer, and depositing a bottom metal layer on the bottom insulating layer;

[0019] S420, removing the top surface metal layer outside the top surface square holes, and the remaining top surface metal layer in each of the top surface square holes forms a top electrode; removing the bottom surface metal layer outside the bottom surface square holes, and the remaining bottom surface metal layer in each of the bottom surface square holes forms a bottom electrode.

[0020] Furthermore, in the step S410, a top metal layer and a bottom metal layer are deposited by DC sputtering;

[0021] Furthermore, in the step S420, ultrasonic stripping is used to remove the top metal layer outside the top square hole and the bottom metal layer outside the bottom square hole.

[0022] Furthermore, in step S500, the oxygen vacancy concentration is controlled by adjusting the X-ray irradiation energy, irradiation dose and irradiation time so that the oxygen vacancy concentration in the X-ray irradiation area is uniformly distributed; the X-ray irradiation energy is 5KeV~20KeV, and the irradiation dose is 5Mrad(Si)~15Mrad(Si).

[0023] The present invention provides a memristor that generates oxygen vacancies by X-ray irradiation and a preparation method thereof. The oxygen vacancy concentration is generated and regulated in the resistive switching layer of the memristor by X-ray irradiation technology, thereby realizing the resistive state switching of the memristor, reducing the threshold voltage and improving the performance stability and radiation resistance of the device. Compared with the traditional gas ion implantation method, the X-ray irradiation method adopted by the present invention has the advantages of simple process, precise control of vacancy generation, and low energy consumption, and is particularly suitable for high-radiation environments and non-volatile memory applications requiring high performance. X-ray irradiation can effectively generate oxygen vacancies without introducing additional impurities or damaging the crystal structure of the resistive switching layer material. Compared with gas ion implantation, the energy and dose of X-ray irradiation are easier to control, and a precise oxygen vacancy concentration gradient can be generated in a specific area of ​​the resistive switching layer. This method reduces the threshold voltage of the memristor and improves the consistency and reliability of resistive state switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0025] Figure 1 The figure is a flow chart of an embodiment of a method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies according to the present invention.

[0026] Figure 2 It is a schematic diagram of the structure after forming a top insulating layer and a bottom insulating layer on the resistive layer.

[0027] Figure 3 It is a schematic diagram of the structure after the top surface square hole array and the bottom surface square hole array are formed.

[0028] Figure 4 Schematic diagram of the structure after forming the top electrode and the bottom electrode.

[0029] Figure 5 This is a schematic diagram of X-ray irradiation.

[0030] Figure 6 This is a comparison of the threshold voltage of the memristor before and after X-ray irradiation.

[0031] Figure 7 The following is a curve showing the change of resistance values ​​of high resistance state and low resistance state with the number of readout times under different readout voltages.

[0032] The accompanying drawings in the specification are numeraled as follows:

[0033] Resistive layer-100; top insulating layer-200; top square hole-210; bottom insulating layer-300; bottom square hole-310; top electrode-400; bottom electrode-500; X-ray-600. DETAILED DESCRIPTION

[0034] The following describes the implementation methods of the present invention through specific examples. The illustrations provided in the following embodiments are only used to schematically illustrate the basic concept of the present invention. The following embodiments and features in the embodiments may be combined with each other without conflict.

[0035] See also Figure 1 , Figure 1 This is a flow chart of an embodiment of a method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies in this embodiment includes the following steps:

[0036] S100, take a resistive layer 100, the resistive layer 100 is made of doped oxide, generally composed of one or more metal compounds. The metal compound of the resistive layer 100 can be a monovalent or polyvalent metal compound, and the metal valence is not less than two-thirds of the highest positive valence of the metal. In this embodiment, a commercial Nb-doped single crystal SrTiO3 substrate is used as the resistive layer 100, the substrate doping mass fraction is 0.7%, and the crystal orientation is <100> .

[0037] S200, please refer to Figure 2 , a top insulating layer 200 and a bottom insulating layer 300 are deposited on the top and bottom surfaces of the single crystal substrate, respectively. The top insulating layer 200 and the bottom insulating layer 300 can be formed by radio frequency magnetron sputtering, atomic layer deposition (ALD), evaporation, pulsed laser deposition, thermal oxidation or chemical vapor deposition (CVD) and the like. In this embodiment, the top insulating layer 200 is deposited on the top surface of the single crystal substrate by radio frequency magnetron sputtering, and the bottom insulating layer 300 is deposited on the bottom surface of the single crystal substrate by radio frequency magnetron sputtering. The thickness of the top insulating layer 200 and the bottom insulating layer 300 is generally 40nm to 60nm.

[0038] S300, see Figure 3 , etching forms a plurality of top surface square holes 210 penetrating the top surface insulating layer 200 and a plurality of bottom surface square holes 310 penetrating the bottom surface insulating layer 300; the plurality of top surface square holes 210 form a top surface square hole 210 array, and the plurality of bottom surface square holes 310 form a bottom surface square hole 310 array. In this embodiment, a negative photoresist process is used to etch the top surface insulating layer 200 to form an array of top surface square holes 210, and to etch the bottom surface insulating layer 300 to form an array of bottom surface square holes 310. The sizes of the top surface square holes 210 and the bottom surface square holes 310 can be the same. In this embodiment, the sizes of the top surface square holes 210 and the bottom surface square holes 310 are both 80μm×80μm.

[0039] S400, see Figure 4, a top electrode 400 is formed in each top surface square hole 210, and a bottom electrode 500 is formed in each bottom surface square hole 310. This step may include the following sub-steps:

[0040] S410, depositing a top metal layer on the top insulating layer 200, and depositing a bottom metal layer on the bottom insulating layer 300. The thickness of the top metal layer can be the same as that of the bottom metal layer, and the top metal layer and the bottom metal layer can be deposited by DC sputtering. The materials of the top metal layer and the bottom metal layer can be Pt, Au, T i N, Pd, Ru, I r, W, Al, Hf, Ti, Ta, V, Fe, Ni, Cu, Zr, TiW, Si single substance. Of course, the materials of the top metal layer and the bottom metal layer can also be one of other metal compounds. In this embodiment, the materials of the top metal layer and the bottom metal layer are Au.

[0041] S420, removing the top metal layer outside the top square holes 210, and the top metal layer remaining in each of the top square holes 210 forms a top electrode 400; removing the bottom metal layer outside the bottom square holes 310, and the bottom metal layer remaining in each of the bottom square holes 310 forms a bottom electrode 500. Ultrasonic stripping can be used to remove the top metal layer outside the top square holes 210 and the bottom metal layer outside the bottom square holes 310.

[0042] S500, please refer to Figure 5 , X-rays 600 are used to irradiate the resistive switching layer 100, and oxygen vacancies are generated in the resistive switching layer 100 by irradiation of the X-rays 600; the irradiation area of ​​the X-rays 600 does not exceed the outside of the memristor, so as to fully irradiate the entire surface of the memristor and generate a uniform oxygen vacancy concentration distribution. Before the X-rays 600 are irradiated, the resistive switching layer 100 can be patterned to determine the irradiation area of ​​the X-rays 600.

[0043] During the irradiation of X-ray 600, the oxygen vacancy concentration can be controlled by adjusting the irradiation energy, irradiation dose and irradiation time of X-ray 600, so that the oxygen vacancy concentration in the irradiation area of ​​X-ray 600 is uniformly distributed; thereby obtaining the required oxygen vacancy concentration gradient, realizing the resistance state switching of the memristor, and obtaining a memristor with accurately controlled oxygen vacancy concentration gradient. In this step, the irradiation energy of X-ray 600 is generally 5KeV to 20KeV, and the irradiation dose is generally 5Mrad (Si) to 15Mrad (Si). In this embodiment, the irradiation energy of X-ray 600 is 10KeV.

[0044] The irradiation of X-rays 600 can effectively generate oxygen vacancies without introducing additional impurities (except Nb) and damaging the crystal structure of the resistive layer 100 material, thereby maintaining the purity of the resistive layer 100. Compared with gas ion implantation, the energy and dose of X-ray 600 irradiation are easier to control, and a precise oxygen vacancy concentration gradient can be generated in a specific area of ​​the resistive layer 100. This method reduces the threshold voltage of the memristor and improves the consistency and reliability of the resistance state switching.

[0045] The threshold voltage of a conventional resistive memory is usually high, requiring a large external voltage to switch the resistance state. Through the oxygen vacancies generated by X-ray 600 irradiation, this embodiment forms a precise oxygen vacancy distribution in the resistive layer 100, thereby reducing the threshold voltage of the device. This improvement significantly reduces the power consumption of the memristor, making it more suitable for low-power non-volatile memory application scenarios. This embodiment tests the threshold voltage of the memristor before and after X-ray 600 irradiation at a typical irradiation dose of 10 Mrad (Si), thereby verifying the performance of the memristor. Please refer to Figure 6 ,Through comparison, it can be seen that the X-ray 600 irradiation method can not only ,control the concentration distribution of oxygen vacancies in the memristor more accurately, but ,can also reduce the threshold voltage of the memristor, thereby improving the ,performance stability and radiation resistance of the device by reducing the threshold voltage.

[0046] In traditional resistive memory designs, high-energy radiation environments may cause resistance characteristics in the memory cells to degrade, and even cause data errors. However, oxygen vacancies generated by X-ray 600 irradiation can significantly enhance the radiation resistance of the resistive layer 100, so that the device can still maintain stable resistance state conversion characteristics in high-energy radiation environments. The memristor design of the present invention can maintain high and low resistance states when the cumulative radiation dose exceeds 10Mrad (Si), without logic confusion or read and write errors. Please refer to Figure 7 This embodiment also tests the change of the resistance value of the high resistance state (HRS) and the low resistance state (LRS) with the number of readout times at two different readout voltages of 0.3V and 0.5V. Figure 7 It can be seen that the resistance values ​​of the memristor in the two resistance states differ by more than one order of magnitude and do not change significantly after 5000 consecutive readouts, proving that it has good resistance state retention characteristics.

[0047] For the Au / Nb:SrTiO3 / Au unit structure in this embodiment, a stable resistance change characteristic must first be formed through a forming process. By forming a top insulating layer 200 and a bottom insulating layer 300, a stable electric field distribution can be formed between the top electrode 400 and the bottom electrode 500 to avoid the current concentration effect. The structure can achieve a stable forming process in a high radiation environment and maintain reliable switching between high and low resistance states. The resistive layer 100 is disposed between the insulating layers containing the top electrode 400 and the bottom electrode 500 to form a good ohmic contact, reduce the electrical contact resistance, and improve the electrical performance of the device.

[0048] The forming process of a memristor refers to the process of activating the memristor once, with the purpose of changing the memristor from its initial high-resistance state to a low-resistance state, so that it has normal memristive characteristics. The operation is as follows:

[0049] During the forming process, the source S of the memristor is grounded, the gate G is connected to V_{g}, and then a FORM voltage is applied to the memristor. This voltage pulse causes the device to change from a high resistance state to a low resistance state.

[0050] The working principle is as follows:

[0051] Memristors usually achieve memory functions based on the resistance transition characteristics of certain materials. Before forming, the microstructure inside the memristor may be in a relatively disordered or unactivated state, resulting in a high resistance. After the forming voltage is applied, physical or chemical changes in the material inside the memristor are induced, forming a specific conductive channel inside the material or changing the transmission characteristics of the carriers, thereby reducing the resistance and enabling it to exhibit obvious memristive characteristics.

[0052] The SET operation also reduces the resistance of the memristor, but forming is a one-time activation process, and the SET operation is after forming, by applying a smaller pulse signal to increase the conductance as the number of pulses increases, further adjusting the resistance state of the memristor; the RESET operation applies a reverse pulse signal to reduce the conductance of the memristor as the number of pulses increases, and increase the resistance, so that the memristor changes from a low resistance state back to a high resistance state.

[0053] When a negative scanning voltage is applied to the top electrode 400, the current flowing through the device increases slowly and increases sharply to the current limit value of 50mA when the voltage reaches 13.4V, which indicates the completion of the forming process. The forming process is essentially a process in which oxygen ions in the Nb:SrTiO3 material migrate under the action of an external high electric field, thereby causing oxygen vacancies to accumulate on one side of the top electrode 400. The reactions involved in the above process can be expressed as:

[0054]

[0055] In the formula, O O are oxygen atoms in normal lattice positions, Oxygen vacancies generated by oxygen ion migration. The large accumulation of oxygen vacancies near the interface can significantly reduce the Schottky barrier, resulting in a significant increase in tunneling current, so that the Au / Nb:SrTiO3 / Au unit changes from an initial high-resistance state to a low-resistance state. A cyclic scanning voltage is further applied to the device to obtain its IV characteristics. When the scanning voltage increases in the positive direction, the resistive switching unit changes from a low-resistance state to a high-resistance state, and when the scanning voltage increases in the negative direction, the resistive switching unit returns to a low-resistance state. This is a reversible bipolar resistance transition process, and its IV characteristics are shown as a typical pinch hysteresis loop. In this embodiment, the method of generating oxygen vacancies by X-ray 600 irradiation can accurately control the oxygen vacancy concentration distribution in the resistive switching layer 100 by simply adjusting the energy, dose and irradiation time of the X-ray 600, thereby overcoming the limitations of the current technology of generating oxygen vacancies by gas ion implantation. Moreover, X-ray 600 irradiation does not require the introduction of a complex gas control system. This preparation process greatly simplifies the difficulty of generating oxygen vacancies and has a simpler preparation process than the traditional gas ion implantation process. The complexity and cost of the overall process are reduced. In addition, the X-ray 600 irradiation method can not only more accurately control the concentration distribution of vacancies, but also greatly reduce the threshold voltage and improve the stability and durability of the memristor, thereby improving its consistency and service life. And the radiation resistance of the device is improved. Compared with the traditional gas ion implantation method, the X-ray 600 irradiation method used in this embodiment has the advantages of simple process, precise control of vacancy generation, and low energy consumption, and is particularly suitable for non-volatile memory applications in high radiation environments and requiring high performance.

[0056] The above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for fabricating a memristor using X-ray irradiation to generate oxygen vacancies, characterized in that: The following steps are involved: S100, obtaining a resistive switching layer, wherein the resistive switching layer is composed of one or more metal compounds; S200, depositing a top insulating layer and a bottom insulating layer on the top surface and the bottom surface of the resistive layer respectively; S300, etching the top surface insulating layer to form a plurality of top surface square holes, and etching the bottom surface insulating layer to form a plurality of bottom surface square holes; the plurality of top surface square holes form a top surface square hole array, and the plurality of bottom surface square holes form a bottom surface square hole array; S400, forming a top electrode in each of the top surface square holes, and forming a bottom electrode in each of the bottom surface square holes; S500, irradiating the resistive switching layer with X-rays to generate a required oxygen vacancy concentration gradient in a predetermined region of the resistive switching layer.

2. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies as claimed in claim 1, characterized in that: In the step S100, the metal compound of the resistive switching layer is a monovalent or polyvalent metal compound, and the metal valence is not less than two-thirds of the highest positive valence of the metal.

3. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies as claimed in claim 1, characterized in that: The resistive layer is a Nb-doped single crystal SrTiO3 substrate with a doping mass fraction of 0.7%. <100> .

4. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies as claimed in claim 1, characterized in that: In the step S200, the thickness of the top insulating layer and the bottom insulating layer is 40nm to 60nm.

5. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies as claimed in claim 1, characterized in that: In the step S300, a negative resist process is used to etch the top insulating layer to form a top square hole array, and to etch the bottom insulating layer to form a bottom square hole array.

6. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies as claimed in claim 1, characterized in that: The size of the top square hole and the bottom square hole is 80 μm×80 μm.

7. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies as claimed in claim 1, characterized in that: The step S400 includes the following sub-steps: S410, depositing a top metal layer on the top insulating layer, and depositing a bottom metal layer on the bottom insulating layer; S420, removing the top surface metal layer outside the top surface square holes, and the remaining top surface metal layer in each of the top surface square holes forms a top electrode; The bottom metal layer outside the bottom square holes is removed, and the remaining bottom metal layer in each of the bottom square holes forms a bottom electrode.

8. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies as claimed in claim 7, characterized in that: In the step S410, a top metal layer and a bottom metal layer are deposited by DC sputtering.

9. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies as claimed in claim 7, characterized in that: In the step S420, ultrasonic stripping is used to remove the top metal layer outside the top square hole and the bottom metal layer outside the bottom square hole.

10. The method for manufacturing a memristor using X-ray irradiation to generate oxygen vacancies according to any one of claims 1 to 9, characterized in that: In the step S500, the oxygen vacancy concentration is controlled by adjusting the irradiation energy, irradiation dose and irradiation time of the X-rays so that the oxygen vacancy concentration in the X-ray irradiation area is uniformly distributed; the irradiation energy of the X-rays is 5KeV to 20KeV, and the irradiation dose is 5Mrad(Si) to 15Mrad(Si).

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