CN112382722B - Nonvolatile resistive random access memory with adjustable writing voltage and preparation method thereof - Google Patents
Nonvolatile resistive random access memory with adjustable writing voltage and preparation method thereof Download PDFInfo
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- CN112382722B CN112382722B CN202011206255.5A CN202011206255A CN112382722B CN 112382722 B CN112382722 B CN 112382722B CN 202011206255 A CN202011206255 A CN 202011206255A CN 112382722 B CN112382722 B CN 112382722B
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Abstract
The invention discloses a nonvolatile resistive random access memory with adjustable writing voltage and a preparation method thereof, belonging to the field of resistive random access memory devices. The memory device includes: the device comprises a substrate, a bottom electrode, a resistance change function layer and a top electrode. The resistance change functional layer is an organic polymer film with nano holes on the surface, which is prepared by spin coating a mixed solution of two polymers. By changing the spin-coating condition of the mixed solution, the size of the film hole can be adjusted, and further the accurate regulation and control of the writing voltage of the device can be realized. The memory device has a simple structure, is easy to process, shows nonvolatile memory characteristics, can realize accurate regulation and control of write-in voltage, and has wide application prospect in the field of information storage.
Description
Technical Field
The invention relates to the technical field of novel semiconductor memories, in particular to a nonvolatile resistive random access memory with adjustable writing voltage and a preparation method thereof.
Background
In recent years, the rapid development of information technology and the "explosive" growth of multimedia applications have placed higher demands on data storage. Therefore, it is a pursuit of mass data storage to obtain a storage device with excellent performance and low cost. The resistive random access memory has been widely focused by researchers because of its simple sandwich structure, high storage density, strong designability, low energy consumption and other advantages.
The memory may be classified into volatile memory, which loses stored data after the device is powered off, and nonvolatile memory, which does not lose stored data due to the device being powered off, according to the type of memory. Nonvolatile memory mainly includes two types, write Once Read Many (WORM) and Flash (Flash) that is re-writable. Among them, the nonvolatile Flash memory has remarkable advantages in the big data age due to its repeatable erasure characteristics. However, the write voltage of the Flash type resistive random access memory is mostly larger so far, and the write voltage is limited by the material and the structure of the Flash type resistive random access memory, but can only be a fixed value, and the write voltage of the Flash type resistive random access memory cannot be adjusted according to the target requirement. Therefore, the existing nonvolatile memory is difficult to meet the requirements of the future information storage field on ultra-low power consumption and multifunctional intelligent storage of the memory, and the development of the nonvolatile memory in industrial application is limited.
The application number is 201510271467.4, the invention is named as a low-formation-voltage resistance random access memory and a preparation method thereof, and the memory in the patent has the function of writing resistance with low power consumption, but has complex preparation process and high preparation cost, and can not realize accurate regulation and control of writing voltage.
Therefore, designing a Flash memory device with a simple manufacturing process, low cost and capability of accurately regulating and controlling the writing voltage is a problem to be solved in the current development of information technology.
Disclosure of Invention
In view of the defects and shortcomings of the conventional memory, the invention aims to provide a nonvolatile resistive random access memory with adjustable writing voltage and a preparation method thereof.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a nonvolatile resistive random access memory with adjustable writing voltage adopts an Indium Tin Oxide (ITO) conductive film as a bottom electrode; preparing a resistive function layer film with nano holes on the surface and adjustable hole size on a bottom electrode by spin coating a mixed solution of two polymers; metal aluminum (Al) was evaporated as the top electrode. The preparation method of the resistive function layer comprises the steps of spin-coating a mixed solution of polymers on a bottom electrode, then placing the mixed solution in a cyclohexane solvent for etching to obtain a resistive function layer film with nano holes on the surface, and controlling the rotation number of a spin-coating instrument to realize the regulation and control of the nano hole size on the surface of the resistive function layer film; through the regulation and control of the nano hole size on the surface of the film of the resistance change functional layer, the accurate regulation and control of the writing voltage of the memory is realized.
A nonvolatile resistive random access memory with adjustable writing voltage is prepared by the following steps:
a) Glass/ITO (substrate/bottom electrode) cleaning treatment;
b) Preparing a resistance change functional layer: preparing an organic polymer film with nano holes on the surface by adopting a mixed solution spin coating method;
c) Preparing a top electrode: vacuum evaporating metallic aluminum as the top electrode.
d) The nonvolatile resistive random access memory with adjustable writing voltage prepared by the steps is tested by a semiconductor tester.
According to a further technical scheme, in the step a), glass/ITO (substrate/bottom electrode) is cleaned by sequentially carrying out ultrasonic treatment on the Glass/ITO in deionized water, ethanol, acetone and deionized water for 15-20min respectively, and drying by high-purity nitrogen; and finally, the substrate is placed into an oxygen plasma cleaner for 3-5min.
According to a further technical scheme, the preparation of the resistance change function in the step b) is that polymethyl methacrylate and polystyrene are respectively dissolved in a certain volume of tetrahydrofuran solvent, and PMMA solution and PS solution with the same concentration are formed through stirring; mixing and stirring PMMA solution and PS solution according to a certain volume ratio to obtain a mixed solution; spin-coating the mixed solution on a bottom electrode for curing, then placing the bottom electrode in a cyclohexane solvent for etching, and drying to obtain the film of the resistance change function layer.
According to a further technical scheme, the concentrations of the PMMA solution and the PS solution are 3-10mg/mL.
According to a further technical scheme, the volume ratio of the PMMA solution to the PS solution is 3:7.
According to a further technical scheme, the rotation speed of the mixed solution in spin coating is 1000-3000rpm, and the time is 30-40s.
According to a further technical scheme, the curing temperature is 70-75 ℃ and the curing time is 10-12min.
According to a further technical scheme, the cyclohexane solvent is at 60-65 ℃ and the etching time is 50-60s.
According to a further technical scheme, the drying temperature is 70-75 ℃ and the drying time is 10-12min.
According to a further technical scheme, the surface of the resistive function layer film prepared by adopting the mixed solution spin coating method comprises nano holes, and the sizes of the holes can be adjusted through the spin coating rate.
According to a further technical scheme, in the step c), the top electrode is prepared by evaporating metal aluminum on the surface of the resistance change functional layer in a vacuum thermal evaporation mode.
According to a further technical scheme, the thickness of the top electrode is 120-150nm.
Advantageous effects
Compared with the prior art, the invention has the following advantages:
1. the invention adopts the raw materials which are easy to obtain and process, the prepared memory has nonvolatile memory characteristics, and the memory can realize data storage under low power consumption.
2. The memory can realize accurate regulation and control of writing voltage from 0.5V to 1.5V, and has low misreading rate and high stability.
3. The preparation method of the device is simple, a series of organic polymer films with nano holes on the surfaces and adjustable hole sizes can be obtained through a solution method, the controllability of the experimental process is high, and the hole sizes are uniform.
Drawings
FIG. 1 is a schematic diagram of a nonvolatile resistive random access memory with adjustable write voltage;
FIG. 2 is an I-V test curve of the memory easy-to-store process of example 1.
FIG. 3 is a scanning image of an Atomic Force Microscope (AFM) of a polymer film at various spin rates, (a) a spin rate of 1,000 rpm (b) a spin rate of 1500rpm (c) a spin rate of 2000rpm (d) a spin rate of 2500rpm (e) a spin rate of 3000rpm;
FIG. 4 is a graph showing the relationship between the writing voltage and the spin-coating speed in the memory easy-to-store process of example 2.
Detailed Description
The invention is described in further detail below with reference to examples and figures.
The following description is only of embodiments of the present invention, and details and applications of the present invention will be apparent to those skilled in the art from this disclosure, and it is intended to cover various modifications and adaptations of the invention without departing from the principles of the invention.
Example 1
As shown in FIG. 1, a structure of a nonvolatile resistive random access memory with adjustable writing voltage is a sandwich structure and comprises a substrate, a bottom electrode, a resistive random access function layer and a top electrode in sequence.
The preparation method of the nonvolatile resistive random access memory with the adjustable writing voltage comprises the following steps:
1) Glass/ITO (substrate/bottom electrode) cleaning process: sequentially putting the materials into deionized water, ethanol, acetone and deionized water, respectively carrying out ultrasonic treatment for 15min, and drying by high-purity nitrogen; and finally, placing the substrate into an oxygen plasma cleaner for 5min.
2) Preparation of polymer mixed solution: polymethyl methacrylate and polystyrene were dissolved in tetrahydrofuran to form 5mg/mL solutions, respectively. A10 mL sample bottle is prepared, a magneton is put into the sample bottle, 3.5mL of polymethyl methacrylate solution with the concentration of 5mg/mL and 1.5mL of polystyrene solution with the concentration of 5mg/mL are added, and the mixture solution is stirred for 5min until the mixture solution is uniform for standby.
3) Preparing a resistance change functional layer with nano holes on the surface: and (3) adopting a mixed solution spin coating method, dripping the prepared PMMA/PS mixed solution on the surface of a Glass/ITO bottom electrode, spin-coating the mixed solution on the surface of the bottom electrode at a rotating speed of 1000rpm for 30s, placing the mixed solution in an oven for curing for 10min, taking out the mixed solution, immersing the mixed solution in a cyclohexane solvent at 60 ℃ for etching for 60s to remove PS, forming a resistive function layer film with nano-pore holes on the surface, and finally placing the resistive function layer film in the oven for drying for 10min.
4) Preparing a top electrode: and evaporating metal aluminum on the surface of the resistance change functional layer in a thermal evaporation mode.
The semiconductor parameter tester is used for testing the electrical property of the obtained memory, so that the device is a typical nonvolatile Flash memory, can finish data storage under lower voltage, has high switching ratio and has excellent performance. From the I-V relationship graph of the memory shown in fig. 2, when a forward scan voltage is applied, the current has a slow rising trend, the device first presents a "high resistance state", when we increase the scan voltage to 0.5V, the current value in the device rapidly rises, indicating that the device is changed from the "high resistance state" to the "low resistance state", this process is the "writing" process of the memory, and after the "writing", the scan voltage continues to increase to 2V and decrease to 0V, and the memory remains in the "low resistance state" all the time; when negative scanning voltage is applied, the device is still in a low-resistance state, when the scanning voltage is increased to about-2V, the device is converted from the low-resistance state to the high-resistance state, and the memory is always kept in the high-resistance state (HRS) in the process that the scanning voltage is continuously increased to-3V and reduced to 0V, so that the device shows flash memory performance.
Example 2
The preparation method of the nonvolatile resistive random access memory with the adjustable writing voltage comprises the following steps:
1) Glass/ITO (substrate/bottom electrode) cleaning process: sequentially putting the materials into deionized water, ethanol, acetone and deionized water, respectively carrying out ultrasonic treatment for 20min, and drying by high-purity nitrogen; and finally, placing the substrate into an oxygen plasma cleaner for 3min.
2) Preparation of polymer mixed solution: polymethyl methacrylate and polystyrene were each dissolved in tetrahydrofuran to form a 3mg/mL solution. A10 mL sample bottle is prepared, a magneton is put into the sample bottle, 3.5mL of polymethyl methacrylate solution with the concentration of 3mg/mL and 1.5mL of polystyrene solution with the concentration of 3mg/mL are added, and the mixture solution is stirred for 5min until the mixture solution is uniform for standby.
3) Preparing a resistance change functional layer with nano holes on the surface: and (3) adopting a mixed solution spin coating method, dripping the prepared PMMA/PS mixed solution on the surface of a Glass/ITO bottom electrode, spin-coating the mixed solution on the surface of the bottom electrode at the rotating speeds of 1000rpm, 1500rpm, 2000rpm, 2500rpm and 3000rpm respectively, setting the spin-coating time of 40s, curing the mixed solution in an oven for 10min, taking out the mixed solution, immersing the mixed solution in a cyclohexane solvent at 65 ℃ to etch for 50s to remove PS, forming a resistive function layer film with nano-pore holes on the surface, and finally drying the resistive function layer film in the oven for 12min.
4) Preparing a top electrode: and evaporating metal aluminum on the surface of the resistance change functional layer in a thermal evaporation mode.
As can be seen from fig. 3, the sizes of the nanoholes of the etched resistive functional layer are continuously reduced with the increase of the spin-coating speed, which is a scanning image of an Atomic Force Microscope (AFM) of the polymer film corresponding to the spin-coating speeds of 1000rpm, 1500rpm, 2000rpm, 2500rpm, and 3000rpm, respectively.
By using a semiconductor parameter tester, the electrical performance of the obtained memory is tested, and the relation diagram of the writing voltage and the spin coating speed of the memory shown in fig. 4 can show that the writing voltage of the memory device prepared by the organic polymer films with holes of different sizes can be accurately regulated and controlled between 0.5V and 1.5V, and the memory has potential application value in the field of high-stability accurate reading and storage.
Claims (7)
1. The nonvolatile resistive random access memory with adjustable writing voltage is characterized in that the memory device comprises a substrate, a bottom electrode, a resistive random access function layer and a top electrode; the resistance change functional layer is an organic polymer film with nano holes on the surface and adjustable hole size; the accurate regulation and control of the writing voltage of the memory are realized through the regulation and control of the nano hole size on the surface of the film of the resistance change functional layer; spin-coating the mixed solution of the polymer on a bottom electrode, and then placing the bottom electrode in a cyclohexane solvent for etching to obtain a resistive function layer film with nano holes on the surface; the regulation and control of the nano hole size on the surface of the film of the resistance change function layer are realized by controlling the revolution of the spin coater; the mixed solution of the polymer is a mixed solution of polymethyl methacrylate (PMMA) solution and Polystyrene (PS) solution.
2. The method for manufacturing the nonvolatile resistive random access memory with adjustable writing voltage according to claim 1, comprising the following steps:
a) Cleaning the Glass substrate/ITO bottom electrode;
b) Preparing a resistance change functional layer: preparing an organic polymer film with nano holes on the surface by adopting polymethyl methacrylate (PMMA) solution and Polystyrene (PS) solution through a spin coating method;
c) Preparing a top electrode: vacuum evaporating metallic aluminum as the top electrode.
3. The method for manufacturing the nonvolatile resistive random access memory with adjustable writing voltage according to claim 2, wherein the method comprises the following steps: the Glass substrate/ITO bottom electrode cleaning treatment in the step a) is that the Glass substrate/ITO bottom electrode cleaning treatment is carried out by sequentially carrying out ultrasonic treatment on the Glass substrate/ITO bottom electrode in deionized water, ethanol, acetone and deionized water for 15-20min respectively, and drying by high-purity nitrogen; and finally, the substrate is placed into an oxygen plasma cleaner for 3-5min.
4. The method for manufacturing the nonvolatile resistive random access memory with adjustable writing voltage according to claim 2, wherein the method comprises the following steps: the preparation of the step b) of the resistance change functional layer comprises the steps of respectively dissolving polymethyl methacrylate and polystyrene in tetrahydrofuran solvent, and stirring to form PMMA solution and PS solution with the same concentration; mixing and stirring PMMA solution and PS solution to obtain mixed solution; spin-coating the mixed solution on a bottom electrode for curing, then placing the bottom electrode in a cyclohexane solvent for etching, and drying to obtain the film of the resistance change function layer.
5. The method for manufacturing the nonvolatile resistive random access memory with adjustable writing voltage according to claim 4, wherein the method comprises the following steps: the concentrations of the PMMA solution and the PS solution are 3-10mg/mL.
6. The method for manufacturing the nonvolatile resistive random access memory with adjustable writing voltage according to claim 4, wherein the method comprises the following steps: the volume ratio of the PMMA solution to the PS solution is 3:7.
7. The method for manufacturing the nonvolatile resistive random access memory with adjustable writing voltage according to claim 4, wherein the method comprises the following steps: the revolution of the spin coating of the mixed solution is 1000-3000rpm.
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| CN109360887A (en) * | 2018-09-18 | 2019-02-19 | 南京工业大学 | A kind of controllable resistance-variable storing device of shift voltage and preparation method thereof |
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