Cu2S resistive random access memory and regulation and control method thereof

Abstract

The invention discloses a Cu2S resistive random access memory and a regulation and control method thereof, and belongs to the technical field of microelectronic devices. The Cu2S nanosheet with the nanometer thickness is prepared on the Si / SiO2 substrate through an ultrathin slice to serve as the functional layer, inert metal electrode layers are deposited at the two ends of the functional layer through laser direct writing and vacuum thermal evaporation processes, complex processes such as doping are not needed, the current and the applied bias voltage are simply controlled and limited, and the photoelectric conversion efficiency is improved. The prepared Cu2S resistive random access memory can show a non-volatile resistance switching behavior, the regulation and control of the non-volatile resistance characteristic in the device are realized, and the introduction of complex ions is avoided; in addition, the non-volatility of the Cu2S resistive random access memory prepared by the method has good consistency, and the Cu2S resistive random access memory has huge application potential in the aspects of neuromorphic calculation and biological synapse simulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of microelectronic devices, and in particular relates to a Cu2S resistive random access memory and a control method thereof. Background Art

[0002] With the rapid development of artificial intelligence and machine learning technologies, the demand for hardware that can efficiently process complex algorithms and large-scale data is growing. Resistive random access memory has attracted much attention due to its many advantages over traditional storage technologies, such as low power consumption, high-speed access, easy integration, and storage-computing fusion. It has gradually been widely used in electronic devices and computer systems. Most of the resistive random access memories reported so far are based on the electrochemical metallization mechanism and valence state transition mechanism that occur in resistive random access materials. The electrochemical metallization mechanism is the migration of metal ions in solid electrolytes under the action of an electric field, resulting in the formation and breakage of metal conductive channels; the valence state transition mechanism is based on the change in the valence state of ions in the material, such as redox reactions, resulting in changes in conductivity. The uncertainty in the formation of such conductive filaments will lead to a decrease in the response speed of resistive random access memory and an increase in power consumption.

[0003] Some scholars have improved the performance of RRAM by doping Li elements in ZnO thin films and changing the doping concentration of Li elements. The switching current ratio of RRAM is improved with the increase of Li doping concentration, but the migration and distribution of doped Li elements will change after long-term use, resulting in device performance degradation. Others have mainly expanded the storage window of RRAM by using RF magnetron sputtering to form InGaZnO thin films as RRAM layers. However, the stability of plasma is crucial to obtaining a consistent and uniform coating when using RF magnetron sputtering to form InGaZnO thin films. The instability of plasma will lead to changes in film performance and thickness, thereby affecting the performance and reliability of RRAM. Others have significantly improved the switching ratio and stability of the RRAM by adding a layer of titanium dioxide film between the bottom electrode and the perovskite film layer, and doped Zr elements into the perovskite film, and significantly reduced the power consumption of the device. However, due to the complex composition of the perovskite structure, the compatibility with traditional processes is challenging, and the preparation cost is high. Therefore, it is very important to study a RRAM with a simple preparation process, easy regulation, and better performance. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a Cu2S resistive random access memory and a control method thereof, so as to solve the technical problem that impurity ions are easily introduced into the Cu2S resistive random access memory and non-volatile control of the device is difficult to achieve.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: to provide a Cu2S resistive random access memory, including: a substrate layer, a functional layer, a left electrode layer and a right electrode layer, the functional layer is arranged on the surface of the substrate layer, and the left electrode layer and the right electrode layer are respectively deposited on both ends of the functional layer.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows:

[0007] Furthermore, the substrate layer is composed of an upper SiO2 layer and a lower Si layer, and the left electrode layer and the right electrode layer are both composed of an upper Au layer and a lower Ti layer.

[0008] Furthermore, the functional layer is a Cu2S functional layer.

[0009] Cu2S is a sulfide material with unique electrochemical properties. The reversible change of the resistance state of Cu2S material under the action of an electric field is used to store data. Under electrical excitation, the Cu in Cu2S material is simply controlled by limiting the current and the applied voltage. + The migration of Cu2S leads to the formation or breaking of conductive filaments, thereby realizing the transition of resistance state, which gives Cu2S resistive memory a significant advantage in achieving high-density storage and fast data processing.

[0010] Furthermore, the thickness of the functional layer is 50-100 nm.

[0011] Furthermore, the thickness of the SiO2 layer is 900-1100 nm, the thickness of the Si layer is 400-600 μm; the thickness of the Au layer is 35-45 nm, and the thickness of the Ti layer is 3-7 nm.

[0012] Furthermore, the distance between the left electrode layer and the right electrode layer is 10-20 μm.

[0013] The present invention also discloses a method for preparing a Cu2S resistive random access memory, comprising the following steps: cleaning the substrate layer, then transferring a Cu2S nanosheet onto the substrate layer, evaporating metal at both ends of the Cu2S nanosheet under a vacuum state to obtain a left electrode layer and a right electrode layer respectively, and finally soaking the sample in acetone for 20-30 minutes to obtain a Cu2S resistive random access memory.

[0014] On the basis of the above technical solution, the present invention can also be improved as follows:

[0015] Furthermore, before evaporating the metal, the electrode pattern is exposed on both ends of the Cu2S nanosheet by laser direct writing.

[0016] The present invention also discloses a method for regulating a Cu2S resistive random access memory, comprising the following steps: contacting two probes with electrode layers at both ends of a functional layer respectively, regulating a limiting current and a scanning voltage of the functional layer of the Cu2S resistive random access memory through a left electrode layer and a right electrode layer, inducing formation of a conductive filament channel in the functional layer, and realizing regulation of the function of the non-volatile resistive random access memory.

[0017] On the basis of the above technical solution, the present invention can also be improved as follows:

[0018] Furthermore, the current is limited to 1 mA and the scanning voltage is -0.7 to 1V.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention uses S atoms to form a rigid skeleton, Cu + Cu2S, a P-type semiconductor material with excellent mobility, is used as the functional layer. The electrode material does not participate in the formation and breaking of the resistive conductive filament channel. Instead, the functional layer material Cu2S produces conductive filaments under the induction of the electric field, which is easy to control.

[0021] 2. The resistive switching functional layer of the Cu2S resistive memory is a single layer, and no complex processes such as doping are required. By simply controlling the limiting current and the size of the applied bias voltage, the Cu2S resistive memory can exhibit non-volatile resistive switching behavior, realize the regulation of the non-volatile resistive switching characteristics in the device, and avoid the introduction of complex ions. The non-volatility of the Cu2S resistive memory prepared by the present invention has good consistency and has great application potential in neuromorphic computing and biological synapse simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of Cu2S resistive random access memory;

[0023] Figure 2 It is the IV curve of Cu2S resistive memory;

[0024] Figure 3 Figure 1 is a transmission electron micrograph of a Cu2S resistive random access memory, wherein Figure (a) is a transmission electron micrograph of Cu2S before voltage is applied, and Figure (b) is a transmission electron micrograph of Cu2S after voltage is applied;

[0025] Figure 4 The IV curve of Cu2S resistive memory with 10 positive and negative scans;

[0026] Figure 5 The high and low resistance state retention characteristic curves of the Cu2S resistive memory;

[0027] Among them, 1. substrate layer; 2. functional layer; 3. left electrode layer; 4. right electrode layer. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described below to facilitate the understanding of the present invention by those skilled in the art. If the specific conditions are not specified in the examples, the methods are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturers are not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

[0029] Example 1

[0030] A Cu2S resistive random access memory, such as Figure 1 As shown, it includes: a substrate layer 1, a functional layer 2, a left electrode layer 3 and a right electrode layer 4, the functional layer 2 is arranged on the surface of the substrate layer 1, and the left electrode layer 3 and the right electrode layer 4 are respectively deposited on the two ends of the functional layer 2; the functional layer 2 is a Cu2S functional layer (with a thickness of 75nm); the substrate layer 1 is composed of an upper SiO2 layer (with a thickness of 1000nm) and a lower Si layer (with a thickness of 500μm); the left electrode layer 3 and the right electrode layer 4 are both composed of an upper Au layer (with a thickness of 40nm) and a lower Ti layer (with a thickness of 5nm), and the distance between the left electrode layer 3 and the right electrode layer 4 is 15μm.

[0031] The preparation method of Cu2S resistive random access memory comprises the following steps: firstly placing a substrate layer 1 (Si / SiO2 substrate) with a size of 2cm×2cm in acetone, anhydrous ethanol and deionized water in turn, ultrasonically cleaning it at 100W for 15min, and blowing it dry with a nitrogen gun, then transferring a Cu2S nanosheet prepared by ultrathin slicing to the substrate layer 1, exposing electrode patterns at both ends of the Cu2S nanosheet by laser direct writing process under vacuum state, and then adopting two-step evaporation to first evaporate a Ti layer and then evaporate an Au layer on the electrode patterns at both ends of the Cu2S nanosheet to obtain a left electrode layer 3 and a right electrode layer 4 respectively, and finally placing the sample in acetone and soaking it for 25min until the electrode pattern is completely clear, cleaning it with anhydrous ethanol and deionized water in turn, and blowing it dry with a nitrogen gun to obtain a Cu2S resistive random access memory.

[0032] Example 2

[0033] A Cu2S resistive random access memory, such as Figure 1As shown, it includes: a substrate layer 1, a functional layer 2, a left electrode layer 3 and a right electrode layer 4, the functional layer 2 is arranged on the surface of the substrate layer 1, and the left electrode layer 3 and the right electrode layer 4 are respectively deposited on the two ends of the functional layer 2; the functional layer 2 is a Cu2S functional layer (with a thickness of 50nm); the substrate layer 1 is composed of an upper SiO2 layer (with a thickness of 900nm) and a lower Si layer (with a thickness of 400μm); the left electrode layer 3 and the right electrode layer 4 are both composed of an upper Au layer (with a thickness of 35nm) and a lower Ti layer (with a thickness of 3nm), and the distance between the left electrode layer 3 and the right electrode layer 4 is 10μm.

[0034] The preparation method of Cu2S resistive random access memory comprises the following steps: firstly placing a substrate layer 1 (Si / SiO2 substrate) with a size of 2cm×2cm in acetone, anhydrous ethanol and deionized water in turn, ultrasonically cleaning it at 100W for 15min, and blowing it dry with a nitrogen gun, then transferring a Cu2S nanosheet prepared by ultrathin slicing to the substrate layer 1, exposing electrode patterns at both ends of the Cu2S nanosheet by laser direct writing process under vacuum state, and then adopting two-step evaporation to first evaporate a Ti layer and then evaporate an Au layer on the electrode patterns at both ends of the Cu2S nanosheet to obtain a left electrode layer 3 and a right electrode layer 4 respectively, and finally placing the sample in acetone and soaking it for 25min until the electrode pattern is completely clear, cleaning it with anhydrous ethanol and deionized water in turn, and blowing it dry with a nitrogen gun to obtain a Cu2S resistive random access memory.

[0035] Example 3

[0036] A Cu2S resistive random access memory, such as Figure 1 As shown, it includes: a substrate layer 1, a functional layer 2, a left electrode layer 3 and a right electrode layer 4, the functional layer 2 is arranged on the surface of the substrate layer 1, and the left electrode layer 3 and the right electrode layer 4 are respectively deposited on the two ends of the functional layer 2; the functional layer 2 is a Cu2S functional layer (with a thickness of 100nm); the substrate layer 1 is composed of an upper SiO2 layer (with a thickness of 1100nm) and a lower Si layer (with a thickness of 600μm); the left electrode layer 3 and the right electrode layer 4 are both composed of an upper Au layer (with a thickness of 45nm) and a lower Ti layer (with a thickness of 7nm), and the distance between the left electrode layer 3 and the right electrode layer 4 is 20μm.

[0037] The preparation method of Cu2S resistive random access memory comprises the following steps: firstly placing a substrate layer 1 (Si / SiO2 substrate) with a size of 2cm×2cm in acetone, anhydrous ethanol and deionized water in turn, ultrasonically cleaning it at 100W for 15min, and blowing it dry with a nitrogen gun, then transferring a Cu2S nanosheet prepared by ultrathin slicing to the substrate layer 1, exposing electrode patterns at both ends of the Cu2S nanosheet by laser direct writing process under vacuum state, and then adopting two-step evaporation to first evaporate a Ti layer and then evaporate an Au layer on the electrode patterns at both ends of the Cu2S nanosheet to obtain a left electrode layer 3 and a right electrode layer 4 respectively, and finally placing the sample in acetone and soaking it for 25min until the electrode pattern is completely clear, cleaning it with anhydrous ethanol and deionized water in turn, and blowing it dry with a nitrogen gun to obtain a Cu2S resistive random access memory.

[0038] Example 4

[0039] A method for regulating a Cu2S resistive random access memory comprises the following steps: using a Keithley 4200 semiconductor characterization system to perform an electrical test on the Cu2S resistive random access memory prepared in Example 1, contacting two probes with the Ti / Au electrode layers at both ends of a functional layer 2, respectively, limiting the current to 1 mA, and scanning the voltage to -0.7 to 1 V.

[0040] The Cu2S resistive memory is scanned in both positive and negative directions. The scan results are as follows: Figure 2 As shown, from the IV curve, it can be seen that when the scanning voltage rises from a negative value to near the Set voltage, the conductivity of the device rises rapidly, and the resistance changes from high resistance to low resistance; when the scanning voltage is swept back, the device still maintains a low resistance and does not change due to the removal of the voltage. When the reverse scanning voltage rises to near the Reset voltage, the conductivity of the device drops rapidly, and the resistance changes from low resistance to high resistance, indicating that the device resistance value at this time is transformed into non-volatile, and the device as a whole exhibits non-volatile characteristics. Figure 3 Figure 2 is a transmission electron micrograph of the Cu2S resistive random access memory in a high resistance state, where (a) is a transmission electron micrograph of Cu2S before voltage is applied, and (b) is a transmission electron micrograph of Cu2S with conductive filaments appearing after voltage is applied. It can be seen that a conductive filament channel is formed in the Cu2S resistive random access memory.

[0041] The Cu2S resistive memory cell was scanned 10 times in both positive and negative directions. Figure 4 The IV curve of the non-volatile Cu2S resistive memory was cycled 10 times, and it can be seen that the device as a whole exhibits non-volatile characteristics and has excellent DC consistency.

[0042] The retention characteristics of the Cu2S resistive memory cell are tested. Figure 5The measurement results of the retention characteristics of the high and low resistance states of the Cu2S resistive random access memory are shown, where HRS represents the high resistance state and LRS represents the low resistance state. It can be seen that the device has good non-volatility.

Claims

1. A Cu2S resistive random access memory, characterized in that: include: A substrate layer (1), a functional layer (2), a left electrode layer (3) and a right electrode layer (4), wherein the functional layer (2) is arranged on the surface of the substrate layer (1), and the left electrode layer (3) and the right electrode layer (4) are respectively deposited on both ends of the functional layer (2).

2. The Cu2S resistive random access memory according to claim 1, characterized in that: The substrate layer (1) is composed of an upper SiO2 layer and a lower Si layer, and the left electrode layer (3) and the right electrode layer (4) are both composed of an upper Au layer and a lower Ti layer.

3. The Cu2S resistive random access memory according to claim 1, characterized in that: The functional layer (2) is a Cu2S functional layer.

4. The Cu2S resistive random access memory according to claim 1, characterized in that: The thickness of the functional layer (2) is 50-100 nm.

5. The Cu2S resistive random access memory according to claim 2, characterized in that: The thickness of the SiO2 layer is 900-1100 nm, the thickness of the Si layer is 400-600 μm; the thickness of the Au layer is 35-45 nm, and the thickness of the Ti layer is 3-7 nm.

6. The Cu2S resistive random access memory according to claim 1, characterized in that: The distance between the left electrode layer (3) and the right electrode layer (4) is 10-20 μm.

7. The method for preparing the Cu2S resistive random access memory according to any one of claims 1 to 6, characterized in that: The following steps are involved: The substrate layer (1) is cleaned, and then the Cu2S nanosheet is transferred onto the substrate layer (1). Metal is evaporated at both ends of the Cu2S nanosheet under vacuum to obtain a left electrode layer (3) and a right electrode layer (4), respectively. Finally, the sample is immersed in acetone for 20-30 minutes to obtain a Cu2S resistive random access memory.

8. The method for preparing the Cu2S resistive random access memory according to claim 7, characterized in that: Before the metal evaporation, the method further includes exposing electrode patterns at both ends of the Cu2S nanosheet by laser direct writing.

9. The control method of the Cu2S resistive random access memory according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: contacting two probes with electrode layers at both ends of a functional layer (2) respectively, regulating the limiting current and scanning voltage of the functional layer (2) of the Cu2S resistive random access memory through a left electrode layer (3) and a right electrode layer (4), inducing the formation of a conductive filament channel in the functional layer (2), and realizing regulation of the function of the non-volatile resistive random access memory.

10. The control method of the Cu2S resistive random access memory according to claim 9, characterized in that: The limiting current is 1 mA, and the scanning voltage is -0.7 to 1V.

Images