CN107681050A - A kind of preparation method of resistance-variable storing device - Google Patents

Abstract

The invention discloses a preparation method of a resistive variable memory. An organic-inorganic composite film material is synthesized with a titanium dioxide/polyethylene glycol system. There are multiple conformations between the organic material and metal oxide nanoparticles to form a dipole moment. The interaction occurs, and the prepared memory unit has no large voltage activation process and good stability. At the same time, the present invention does not need to rely on expensive equipment.

Description

A kind of preparation method of resistive variable memory

technical field

The invention belongs to the technical field of ultra-large-scale integrated circuits, and relates to a material for improving the characteristics of a transition-group metal oxide-based resistive memory and a preparation method for the resistive memory. The introduction of the material can regulate the behavior of oxygen vacancies.

Background technique

At present, advanced memory manufacturers are mass-producing 3D NAND memory, because the storage capacity per unit area of the previous generation of planar flash memory has reached the physical limit. Due to the continuous reduction of physical size, traditional flash memory has the problem of reduced reliability due to charge leakage. In addition, people have put forward higher and higher requirements for electronic products, including key parameters such as read/erase speed, capacity, and reliability. . 3D NAND memory is developed on the basis of planar NAND memory (that is, 2D NAND memory), and its storage capacity has been significantly improved. However, it is a new generation of storage technology-resistive memory that really has breakthroughs in storage parameters such as read/erase speed, capacity, power consumption, time retention characteristics, tolerance, and noise resistance.

At present, the resistance switching behavior mainly occurs in transition metal oxides, such as CuO _x , TiO _x , AlO _x , WO _x , NiO _x , ZnO _x , TaO _x , HfO _x and other materials. Under the action of an external electric field, the film will migrate and accumulate oxygen vacancies to form a conductive channel and transform to a low-resistance state. During the initialization process, the device often requires a voltage several times higher than the normal write voltage (several volts) to be activated in order to perform normal write and erase operations. In this process, a large voltage (tens of volts or tens of volts) will cause uncontrollable changes in the crystal structure of the film (the device breaks down and loses the function of storing data). A certain amount of oxygen vacancies are generated in the film for writing and erasing operations.

During thin film deposition, oxygen atoms in the plasma form bonds with individual metal atoms, forming a metal oxide network on the substrate. Regardless of the stoichiometric state or not, one needs a large voltage to break the bond between the metal and oxygen to form freely moving oxygen ions, thereby generating the migration of oxygen vacancies.

The resistive variable memory in the prior art has the following problems: the memory cell (capable of storing a data, such as 0 or 1) needs a voltage many times greater than the read and write voltage (several volts) to activate during the initialization process, and there are relatively The high probability will cause the memory cell to break down and fail; the traditional methods of preparing transition metal oxide thin films include physical vapor deposition, laser pulse deposition, atomic layer deposition and other vacuum coating technologies, which have the advantages of high equipment procurement costs, High maintenance cost, long production cycle and other limiting factors.

Contents of the invention

The purpose of the present invention is to provide a low-cost, high-reliability method for preparing a resistive variable memory.

To this end, the present invention adopts the following technical solution: a preparation method of a resistive variable memory, comprising the following steps:

1) Clean and dry the conductive glass for later use;

2) Dissolve titanium dioxide particles with a particle size of 20-50 nm and polyethylene glycol with a molecular weight of 2000-6000 in absolute ethanol, wherein the mass/volume ratio (g/ml) of titanium dioxide particles to absolute ethanol is 1 -5%, the mass/volume ratio (g/ml) of polyethylene glycol to absolute ethanol is 0.5-3%, ultrasonically dispersed;

3) Spin-coat the solution obtained in step 2) on the conductive glass in step 1) to form a film with a glue equalizer at a speed of 3000~4000rpm and a time of 30~90s;

4) Anneal in a tube furnace at 150~205°C for 1~3 hours under the protection of argon atmosphere;

5) Define the shape and size of the top electrode by using a metal mask or photolithography process, and the diameter of the electrode is 0.5-50 microns;

6) A metal top electrode with a thickness of 200-500 nm is prepared by thermal evaporation coating method.

The present invention synthesizes an organic-inorganic composite film material with a titanium dioxide/polyethylene glycol system. There are various conformations between the organic material and metal oxide nanoparticles to form dipole moments and interact with each other, and the prepared storage unit It has no large voltage activation process and good stability. At the same time, the present invention does not need to rely on expensive equipment.

Description of drawings

Below in conjunction with accompanying drawing and embodiment of the present invention will be described in further detail

Fig. 1 is the method block diagram of embodiment;

Fig. 2 is the schematic cross-sectional view of embodiment product;

Fig. 3 is the voltage-current characteristic figure of embodiment;

Fig. 4 is a diagram showing fatigue resistance characteristics of the examples.

Marked in the figure are: insulating substrate layer 4 , bottom electrode layer 3 , resistive medium layer 2 , and top electrode layer 1 .

detailed description

See attached picture. The resistive variable memory described in this embodiment has a multi-layer stacked three-dimensional structure, including an insulating substrate layer 4 , a bottom electrode layer 3 , a resistive variable medium layer 2 , and a top electrode layer 1 from bottom to top.

The preparation process of the resistive memory device is as follows:

1) First, ultrasonically clean the FTO or ITO conductive glass with acetone (analytical grade) and absolute ethanol (analytical grade), then rinse with deionized water and blow dry with high-purity nitrogen;

2) Dissolve 1.0-2.5 grams of titanium dioxide nanoparticles (with a size of 20-50 nanometers) and 0.5-1.5 grams of polyethylene glycol (with a molecular weight of 2000-6000) in 50-100 ml of absolute ethanol, and ultrasonically disperse;

3) Spin-coat film on conductive glass with glue equalizer, the parameters are: speed 3000~4000 rpm, time 30~90s;

4) Use a tube furnace to anneal at 150~205 °C for 1~3 hours under the protection of argon atmosphere;

5) Define the shape and size of the top electrode by using a metal mask or photolithography process, and the diameter of the electrode is 0.5-50 microns;

6) Prepare a silver (or gold, platinum, tungsten) top electrode with a thickness of 200-500 nanometers by thermal evaporation coating method.

Fig. 3 is the first current-voltage characteristic diagram of the resistive dielectric layer heat-treated at 150°C for 1 hour in the embodiment, the horizontal axis is voltage/V, and the vertical axis is current/A. It can be seen from Figure 3 that when the electrical characteristics are characterized at room temperature, the device transitions from the high resistance state (HRS) to the low resistance state (LRS) when the first scan voltage is less than 1.0 V, and the process is slow. The changing state is conducive to maintaining the stability of the thin film crystal structure and improving the reliability of the device. As the number of scans increases, the current-voltage (I-V) curve of the device will be in a stable state.

Fig. 4 is a diagram of the anti-fatigue characteristics of the resistive dielectric layer at room temperature after heat treatment at 150° C. for 1 hour in the embodiment, the horizontal axis is the number of scans, and the vertical axis is resistance/Ω. It can be seen from Figure 4 that at room temperature, the read voltage is 0.1V, and the memory cell can withstand 100 cycles without significant degradation of the high and low resistance states, showing good fatigue resistance.

Claims (1)

1. A kind of 1. preparation method of resistance-variable storing device, it is characterised in that：Comprise the following steps：

   1）Electro-conductive glass cleaning drying is standby；

   2）The polyethylene glycol that the titanium dioxide granule that particle diameter is 20 ~ 50 nanometers is 2000 ~ 6000 with molecular weight is dissolved in anhydrous second In alcohol, the wherein mass/volume ratio of titanium dioxide granule and absolute ethyl alcohol（g/ml）For 1-5%, polyethylene glycol and absolute ethyl alcohol Mass/volume ratio（g/ml）For 0.5-3%, ultrasonic disperse；

   3）With equal glue machine by step 2）The solution of gained is in step 1）Electro-conductive glass on spin coating film, rotating speed 3000 ~ 4000 Rpm, 30 ~ 90s of time；

   4）Annealed 1 ~ 3 hour for 150 ~ 205 DEG C under argon atmospher protection with tube furnace；

   5）The shape and size of top electrode, 0.5 ~ 50 micron of the diameter of electrode are defined using metal mask plate or photoetching process；

   6）The metallic top electrode that thickness is 200 ~ 500 nanometers is prepared using thermal evaporation coating method.