CN102623635A - A resistive random read memory based on tin dioxide and its preparation method - Google Patents

Abstract

The invention discloses a resistive random read memory based on tin dioxide and a preparation method thereof. The reading and writing life and stability of the existing resistive memory are relatively poor. The memory of the present invention is composed of a heavily doped silicon substrate, a tin dioxide thin film, and a metal thin film electrode. The tin dioxide thin film is located between the heavily doped silicon substrate and the metal thin film electrode. The lower electrode and the metal thin film electrode are used as the upper electrode of the resistive random access memory. The method of the invention is to clean the heavy-doped silicon substrate by adopting the semiconductor standard cleaning process; then adopt the magnetron sputtering method to deposit the tin dioxide film on the heavy-doped silicon substrate; thin film electrodes. The invention adopts the novel tin dioxide thin film as the resistive layer in the resistive random read memory, which can obtain good resistance transition characteristics.

Description

A resistive random read memory based on tin dioxide and its preparation method

technical field

The invention belongs to the technical field of non-volatile random read memory, and relates to a resistive random read memory based on tin dioxide and a preparation method thereof.

Background technique

Memory is an indispensable and important electronic device in the modern information society, and occupies a considerable share in the electronic market. With the continuous development of the electronic information industry, memory is developing in the direction of higher density, higher speed, lower energy consumption, and non-volatility. Traditional dynamic random access memory and static random access memory have fast read and write speeds, but the stored information is quickly lost after power failure, and it needs to be refreshed continuously to maintain the stored information, so it consumes a lot of energy. Non-volatile memory has the advantage of being able to store information for a long time after a power failure, and does not need to be refreshed, so the energy consumption is very low. It has been widely used in mobile phones, digital cameras, mobile storage and other products. According to statistics, the capacity of global non-volatile flash memory has doubled every year in the past ten years, and the market size is getting bigger and bigger.

However, compared with DRAM and SRAM, the device structure and working principle of currently used non-volatile flash memory determine its lower storage speed. Therefore, it is of great significance to research and develop a new generation of memory which not only has the same storage speed as DRAM or SRAM, but also has the characteristics of maintaining information after power failure of non-volatile memory.

As a new type of non-volatile random access memory, resistive random access memory has the advantages of low power consumption, simple structure, fast storage speed, and high-density integration, and is expected to become the next generation of general-purpose non-volatile memory. The structure of resistive memory is very simple, and it is a sandwich structure based on MIM, where M is generally a metal electrode, and I is an insulating layer or a semiconductor film, including: binary metal oxide films (BMOs), perovskite oxides, chalcogenides compounds and organics etc. Among these materials, binary metal oxide thin films are considered to be a class of materials that are expected to be applied to resistive memories due to their simple material components, simple preparation methods, and compatibility with silicon integrated circuit technology, and they are also the most studied ones. class material. Such as Nb ₂ O ₅ , Al ₂ O ₃ , Ta ₂ O ₅ , TiO ₂ , NiO, ZrxO, _Cux O, ZnO, etc. Among them, NiO and TiO ₂ are the most concerned materials. As an important semiconductor material, SnO ₂ has obvious advantages in integration and low manufacturing cost, and has attracted extensive attention due to its unique electrical, magnetic and catalytic properties. However, the research on the application of _SnO2 in resistive memory has not been reported.

Contents of the invention

Aiming at the deficiencies of the prior art, the invention provides a resistive random read memory based on a tin dioxide film and a preparation method thereof.

The technical scheme that the present invention solves technical problem to take is:

A resistive random access memory based on tin dioxide, the memory is composed of a heavily doped silicon substrate, a tin dioxide film, and a metal film electrode, and the tin dioxide film is located between the heavily doped silicon substrate and the metal film electrode, The heavily doped silicon substrate is used as the lower electrode of the resistive random read memory, and the metal film electrode is used as the upper electrode of the resistive random read memory.

The resistivity of the heavily doped silicon substrate is less than 0.1Ω·cm.

The thickness range of the tin dioxide thin film is 10-100nm.

The metal thin film electrode is a solid metal material at a temperature of 100°C. The metal material is preferably gold, platinum, copper, aluminum, titanium or nickel.

The method for preparing the above-mentioned resistive RAM comprises the following steps:

Step 1. Clean the heavily doped silicon substrate by using a semiconductor standard cleaning process;

Step 2. Depositing a tin dioxide film on a heavily doped silicon substrate by magnetron sputtering;

Step 3. Prepare a metal thin film electrode on the tin dioxide thin film by electron beam evaporation.

In step 2, the tin dioxide film is prepared by magnetron sputtering, the specific conditions are: the ratio of the flow rate of argon to oxygen is 6-0.75, the sputtering power is 6W, the sputtering time is 2-20min, and the sputtering time is 2-20min. Pure metal tin target.

Beneficial effects of the present invention: the present invention can obtain good resistance transition characteristics by adopting a novel tin dioxide thin film as the resistive layer in the resistive random access memory. At the same time, compared with the memory cells of ordinary resistive random access memory, this new type of resistive random access memory exhibits excellent transition and memory characteristics between high and low resistance states under continuous scanning excitation of DC voltage, The difference between the high and low resistance states can be greater than 10 ² times, the device requires less power consumption, is suitable for low-voltage circuits of computers, has stable device performance, and is well compatible with silicon integrated circuit technology. These characteristics indicate that the present invention has potential application value in the field of non-volatile memory devices.

Description of drawings

Fig. 1 is a schematic diagram of the memory structure of the present invention;

Fig. 2 is the I-V characteristic diagram of the memory device prepared in embodiment 1;

FIG. 3 is the variation of the resistance value of the memory prepared in Example 1 with the number of switching cycles in the high resistance state and the low resistance state.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing:

As shown in Figure 1, a memory cell of a resistive random access memory includes: a resistive memory with a metal film electrode/tin dioxide film/heavily doped silicon substrate structure. The memory is composed of heavily doped silicon substrate 1 , tin dioxide film 2 , and metal film upper electrode 3 . Wherein, the metal of the upper electrode of the memory cell may be gold, platinum, copper, aluminum, titanium, or nickel. The tin dioxide film is used as the working layer of the memory cell, and plays a role of resistance conversion. Heavily doped silicon is used as the lower electrode and substrate of the memory cell.

The invention adopts the magnetron sputtering method to prepare the tin dioxide thin film. The resistivity of the heavily doped silicon substrate used is 10 ^-2 to 10 ^-3 Ω·cm. The heavy-doped silicon substrate was cleaned by the standard semiconductor cleaning process, and placed in a magnetron sputtering apparatus. When the background vacuum of the chamber was pumped to 8×10 ^-5 Pa, a certain proportion of argon and oxygen was introduced to make the chamber To achieve the working pressure of 0.25Pa, the ratio of argon and oxygen in the mixed atmosphere is controlled by changing the flow of argon and oxygen, and the flow ratio of argon and oxygen is 6-0.75. A high-purity metal tin target was used to deposit tin dioxide thin films at room temperature. during sputtering. The sputtering voltage is 300V, the sputtering current is 0.02A, and the sputtering power is 6W. By changing the sputtering time, different thicknesses of tin dioxide films can be obtained. The sputtering time ranges from 2 to 20 minutes, and the film thickness ranges from 10 to 100nm. . A circular metal electrode with a diameter of 600 μm was deposited on the tin dioxide film through a stainless steel mask in an electron beam evaporation coater. The device obtained in this way has simple preparation process, reliable performance, high reading and writing life and low power consumption.

The tin dioxide film can be conventionally used in the field to prepare a tin dioxide film by physical deposition, and the deposition process parameters of the present invention are as follows:

Argon to oxygen ratio 6～0.75

Sputtering time 2～20min

Film Thickness 10～100nm

More preferably, the process parameters are as follows:

Argon to oxygen ratio 1.5

Sputtering time: 5min

Film Thickness 30nm

The purpose and effects of the present invention will become more apparent by referring to the specific embodiments of the present invention in detail below.

Example 1

Use the magnetron sputtering method to deposit tin dioxide film on a clean heavily doped silicon substrate. When the background vacuum of the cavity is 8×10-5Pa, argon and oxygen are introduced to make the cavity reach 0.15Pa. Pressure, in which the flow rate of argon gas is 60 sccm, the flow rate of oxygen gas is 40 sccm, and the ratio of argon gas to oxygen gas is 1.5:1. During the sputtering process, the sputtering voltage was 300V, the sputtering current was 0.02A, the sputtering power was 6W, the sputtering time was 5min, and the thickness of the film was 25nm. Then electron beam evaporation is used to prepare a metal thin film electrode on the tin dioxide thin film through a mask method, and the electrode is a circular copper electrode with a diameter of 100 μm. The structure of the storage unit is shown in Figure 1. The current-voltage characteristic test results of the memory cell are shown in FIG. 2 . When the scanning voltage is 1.4V, the device is in the set state, and the memory cell changes from a high-resistance state to a low-resistance state, and can maintain a low-resistance state without applying voltage; when the scanning voltage is 0.18V, the device In the reset state, the memory cell changes from a low-resistance state to a high-resistance state, and can maintain a high-resistance state when no voltage is applied. The set voltage and reset voltage of the storage unit are both between 0 and +1.5V, which greatly reduces the power consumption of the device, and is suitable for low-voltage circuits of computers. Fig. 3 is the change of the resistance value of the prepared memory in the high-resistance state and the low-resistance state with the number of switching cycles. It can be seen from the figure that this new type of resistive memory exhibits excellent transition and memory characteristics between high and low resistance states under the excitation of continuous scanning of DC voltage, and the difference between the resistance value of the high and low resistance states is greater than 10 ² times , in the process of 30 continuous cycles of high and low resistance states, the resistance value of the high and low resistance states shows better stability, these characteristics indicate that the present invention has potential application value in the field of non-volatile memory devices.

Example 2

Deposit a tin dioxide film on a clean heavily doped silicon substrate by DC magnetron sputtering. When the background vacuum of the cavity is 8×10 ^-5 Pa, argon and oxygen are introduced to make the cavity reach 0.15 Pa. The working pressure is 60 sccm for argon, 40 sccm for oxygen, and the ratio of argon to oxygen is 1.5:1. During the sputtering process, the sputtering voltage was 300V, the sputtering current was 0.02A, the sputtering power was 6W, the film sputtering time was 10min, and the thickness of the film was 60nm. Electron beam evaporation is used to prepare metal thin film electrodes on tin dioxide thin films by masking method, and the electrodes are circular copper electrodes with a diameter of 100 μm. The structure of the storage unit is shown in Figure 1.

The foregoing embodiments are only examples of the present invention. Although the best embodiment of the present invention and accompanying drawings are disclosed for illustrative purposes, those skilled in the art can understand that: without departing from the spirit and scope of the present invention and the appended claims Inside, various substitutions, changes and modifications are possible. Therefore, the present invention should not be limited to what is disclosed in the preferred embodiments and drawings.

Claims (7)

1. the resistor type random access based on tin ash reads memory; It is characterized in that: this memory is made up of heavily doped silicon substrate, tin dioxide thin film, metal film electrode; Tin dioxide thin film is between heavily doped silicon substrate, metal film electrode; Heavily doped silicon substrate reads the bottom electrode of memory as resistor type random access, and metal film electrode reads the top electrode of memory as resistor type random access.

2. resistor type random access as claimed in claim 1 reads memory, it is characterized in that: the resistivity of heavily doped silicon substrate is less than 0.1 Ω cm.

3. resistor type random access as claimed in claim 1 reads memory, it is characterized in that: the thickness range of tin dioxide thin film is 10～100nm.

4. resistor type random access as claimed in claim 1 reads memory, it is characterized in that: metal film electrode is for being the metal material of solid under 100 ℃ of temperature.

5. resistor type random access as claimed in claim 4 reads memory, it is characterized in that: described metal material is selected gold, platinum, copper, aluminium, titanium or nickel for use.

6. prepare the method that resistor type random access according to claim 1 reads memory, it is characterized in that this method may further comprise the steps:

Step 1. adopts semiconductor standard cleaning technology to clean heavily doped silicon substrate;

Step 2. adopts magnetron sputtering method on heavily doped silicon substrate, to deposit tin dioxide thin film;

Step 3. adopts electron-beam vapor deposition method to prepare metal film electrode on tin dioxide thin film.

7. preparation method as claimed in claim 6 is characterized in that: in the step 2, utilize magnetron sputtering method to prepare tin dioxide thin film; Actual conditions is: argon gas and oxygen flow proportion are 6～0.75; Sputtering power is 6W, and sputtering time 2～20min uses metal tin target during sputter.