CN102623636A - A resistive random read memory based on bismuth oxide film and its preparation method - Google Patents

Abstract

The invention discloses a resistive random read memory based on a bismuth oxide thin film 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 bismuth oxide thin film, and a metal thin film electrode. The bismuth oxide thin film is located between the heavily doped silicon substrate and the metal thin film electrode, and the heavily doped silicon substrate is used as the lower electrode of the resistive random access memory. , the metal film electrode is used as the upper electrode of the resistive random access memory. The method of the invention is to clean the heavily doped silicon substrate by adopting the semiconductor standard cleaning process; then adopting the magnetron sputtering method to deposit a bismuth oxide thin film on the heavily doped silicon substrate; . The invention can simplify the manufacturing process of the memory and is well compatible with the silicon integrated circuit process.

Description

A resistive random read memory based on bismuth oxide film 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 film and a preparation method thereof.

Background technique

In recent years, the increasing consumption of portable devices has rapidly expanded the non-volatile memory market. As a mainstream non-volatile memory, flash memory has a cell structure evolved from the traditional metal-oxide-semiconductor field-effect transistor (MOSFET), has a mature manufacturing process, and occupies more than 90% of the market share of non-volatile memory. Widely used in information storage of portable devices. 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, the way that flash memory utilizes electric charge to store information will encounter great challenges in the CMOS process of 22nm and below. Therefore, ferroelectric memory, magnetoresistive memory, phase-change memory, resistance memory and other new non-volatile memories that store information in a non-charge manner have received great attention. Among them, resistive random access memory has the advantages of high speed, low power consumption, simple structure, and high-density integration, and is considered to be 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. Bismuth oxide (Bi ₂ O ₃ ) is an important oxide semiconductor material, which shows many attractive properties and has attracted more and more attention. In recent years, bismuth oxide thin film materials have attracted great interest in applications, and have been applied in electronic functional materials, electrolyte materials, optoelectronic materials, medical composite materials, high-temperature superconducting materials, catalysts, etc. However, there is no report on the application of bismuth oxide in resistive memory.

Contents of the invention

Aiming at the deficiencies of the prior art, the invention provides a resistive random read memory based on a bismuth oxide 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 a bismuth oxide thin film, the memory is composed of a heavily doped silicon substrate, a bismuth oxide thin film, and a metal thin film electrode. The bismuth oxide thin film is located between the heavily doped silicon substrate and the metal thin film electrode. The 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 bismuth oxide thin film is 30-200nm.

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 heavy-doped silicon substrate with semiconductor standard cleaning process;

Step 2. Depositing a bismuth oxide film on a heavily doped silicon substrate by magnetron sputtering;

Step 3. Prepare a metal thin film electrode on the bismuth oxide thin film by electron beam evaporation.

In step 2, the bismuth oxide thin film is prepared by magnetron sputtering. The specific conditions are: the flow rate ratio of argon to oxygen is 20-7, the substrate temperature is 25°C-300°C, the sputtering power is 30W, and the sputtering time is 5-30min, high-purity metal bismuth target is used for sputtering.

Beneficial effects of the present invention: the present invention can obtain good resistance transition characteristics by using a novel bismuth oxide thin film as the resistive layer in the resistive random access memory. This new type of resistive random access memory exhibits transition and memory characteristics between high and low resistance states under the excitation of continuous scanning of DC voltage, the performance of the device is stable, and it 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 an I-V characteristic diagram of the memory prepared in Example 2. FIG.

Detailed ways

This embodiment is achieved through the following technical solutions: a storage unit of a resistive random access memory, including: a resistive memory with a structure of a metal thin film electrode/bismuth oxide thin film/heavily doped silicon substrate. The memory is composed of heavily doped silicon substrate 1 , bismuth oxide 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 bismuth oxide thin film is used as the working layer of the memory cell, and plays the 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 bismuth oxide 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 0.5Pa, 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 20-7. Bismuth oxide films were prepared at different deposition temperatures using high-purity metal bismuth targets, and the substrate temperature ranged from 25°C to 300°C. During the sputtering process, the sputtering power is 30W, and bismuth oxide films with different thicknesses are obtained by changing the sputtering time. The sputtering time ranges from 5 to 30 minutes, and the film thickness is 30 to 200 nm. A circular metal electrode with a diameter of 100 mm is deposited on the bismuth oxide film through a stainless steel mask in an electron beam evaporation coater. The obtained device has a simple preparation process and reliable performance.

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

Argon to oxygen ratio 20～7

Sputtering time: 5～30min

Film thickness 30～200nm

Substrate temperature 25℃～300℃

More preferably, the process parameters are as follows:

Argon to oxygen ratio 20～10

Sputtering time: 10～25min

Film thickness 70～180nm

Substrate temperature 100℃～300℃

More preferably, the process parameters are as follows:

Argon to oxygen ratio 18～15

Sputtering time: 10～15min

Film thickness 70～100nm

Substrate temperature 200℃～250℃

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 bismuth oxide film on a clean heavily doped silicon substrate. When the background vacuum of the cavity is 8×10 ^-5 Pa, argon and oxygen are introduced to make the cavity reach 0.5 Pa. Pressure, in which the flow rate of argon gas is 45 sccm, the flow rate of oxygen gas is 3 sccm, and the ratio of argon gas to oxygen gas is 15. During the sputtering process, the sputtering power is 30W, the sputtering time is 15min, the thickness of the film is 100nm, and the substrate temperature is 250°C. Then electron beam evaporation is used to prepare a metal thin film electrode on the bismuth oxide thin film through a mask method, and the electrode is a circular gold 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 4.9V, 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 3.5V, 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.

Example 2

Use the magnetron sputtering method to deposit bismuth oxide film on a clean heavily doped silicon substrate. When the background vacuum of the cavity is 8×10 ^-5 Pa, argon and oxygen are introduced to make the cavity reach 0.5 Pa. Pressure, wherein the flow rate of argon gas is 54 sccm, the flow rate of oxygen gas is 3 sccm, and the ratio of argon gas to oxygen gas is 18. During the sputtering process, the sputtering power is 30W, the sputtering time is 10min, the thickness of the film is 70nm, and the substrate temperature is 250°C. Then electron beam evaporation is used to prepare a metal thin film electrode on the bismuth oxide thin film by 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. 3 . When the scanning voltage is 2.8V, 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 1.6V, 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 foregoing embodiments are only examples of the present invention. Although the best embodiment of the present invention and the 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. A resistive random access memory based on a bismuth oxide thin film is characterized in that: the memory is made of a heavily doped silicon substrate, a bismuth oxide thin film, and a metal thin film electrode, and the bismuth oxide thin film is located on a heavily doped silicon substrate, a metal thin film Between the electrodes, the heavily doped silicon substrate is used as the lower electrode of the resistive random read memory, and the metal thin film electrode is used as the upper electrode of the resistive random read memory. 2. The resistive random access memory according to claim 1, wherein the resistivity of the heavily doped silicon substrate is less than 0.1Ω·cm. 3. The resistive random access memory according to claim 1, wherein the bismuth oxide thin film has a thickness ranging from 30 nm to 200 nm. 4. The RRAM as claimed in claim 1, wherein the metal film electrode is a solid metal material at a temperature of 100°C. 5. The resistive random access memory as claimed in claim 4, wherein the metal material is selected from gold, platinum, copper, aluminum, titanium or nickel. 6. prepare the method for resistive random access memory as claimed in claim 1, it is characterized in that the method comprises the following steps: Step 1. Clean the heavily doped silicon substrate by using a semiconductor standard cleaning process; Step 2. Depositing a bismuth oxide film on a heavily doped silicon substrate by magnetron sputtering; Step 3. Prepare a metal thin film electrode on the bismuth oxide thin film by electron beam evaporation. 7. The preparation method according to claim 6, characterized in that: in step 2, the bismuth oxide thin film is prepared by magnetron sputtering, the specific conditions are: the flow ratio of argon to oxygen is in the range of 20 to 7, the substrate temperature The temperature is 25 ℃ ~ 300 ℃, the sputtering power is 30W, the sputtering time is 5 ~ 30min, and the metal bismuth target is used for sputtering.

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