CN116200704A - A kind of preparation method of metal oxide thin film and oxide thin film - Google Patents

Abstract

The application provides a method for preparing a metal oxide thin film and the oxide thin film. The method includes: performing at least two sputtering processes on the surface of the substrate in a vacuum reaction chamber to obtain a metal oxide film. The preparation method of the present application performs sputtering and annealing step by step, the annealing process is more sufficient, the crystallinity is improved, and the purity of the metal oxide in the film component is greatly improved.

Description

A kind of preparation method of metal oxide thin film and oxide thin film

technical field

The invention relates to the field of thin film manufacturing, in particular to a method for preparing a metal oxide thin film and the oxide thin film.

Background technique

Currently, vanadium dioxide (VO ₂ ) has attracted considerable attention as a phase change material that undergoes a reversible metal-insulator phase transition at temperatures close to 68°C. Since phase transitions lead to drastic changes in electrical, magnetic, and optical properties, there are many potential applications. Examples include switchgear, switchable/tunable metamaterials, switchable/tunable antennas and microwave devices, sensors, smart windows, etc.

The preparation methods of vanadium dioxide include sol-gel method, pulsed laser deposition (PLD), chemical vapor deposition (CVD) and physical vapor deposition (PVD). Among them, the physical vapor deposition preparation method has the advantages of fast deposition speed, good film uniformity, and composition close to the target material composition. The sputtering method in physical vapor deposition has obvious advantages. When vanadium dioxide is prepared by sputtering, the thickness is easy to control and the film adhesion is relatively high. The disadvantage of using the sputtering method to prepare vanadium dioxide is that the prepared film has a high purity and often contains other valence states of vanadium oxide.

Contents of the invention

In order to solve the problems in the prior art, the present invention provides a method for preparing a metal oxide thin film and the oxide thin film, which can greatly improve the purity of the thin film components.

In order to achieve the above object, the application provides a method for preparing a metal oxide film, comprising:

In a vacuum reaction chamber, at least two sputtering processes are performed on the surface of the substrate to obtain a metal oxide film.

In a preferred embodiment, each sputtering process includes: using a sputtering method, after sputtering metal oxide on the surface of the substrate at working temperature, raising the temperature of the substrate and performing annealing to obtain a metal oxide thin film.

In a preferred embodiment, the at least two sputtering processes include the first sputtering process and the second sputtering process carried out in sequence, wherein the working temperature of the substrate in the first sputtering process is lower than that of the second sputtering process. The operating temperature of the substrate for the sputtering process.

In a preferred embodiment, the sputtering metal oxide on the surface of the substrate includes: using working gas ions to bombard the metal target, and the sputtered metal ions interact with oxygen to form a metal oxide film on the surface of the substrate.

In a preferred embodiment, the working gas is an inert gas.

In a preferred embodiment, the working temperature of the substrate during the sputtering process is 200-400°C.

In a preferred embodiment, the flow rate of the working gas introduced into the vacuum reaction chamber is 25-30 sccm.

In a preferred embodiment, the flow rate of oxygen introduced into the vacuum reaction chamber is 1-1.5 sccm.

In a preferred embodiment, the metal is vanadium and the metal oxide is vanadium dioxide.

In a preferred embodiment, the sputtering is DC magnetron sputtering.

The present application also provides a metal oxide thin film prepared by the above method.

The preparation method of the embodiment of the present application performs sputtering and annealing step by step, the annealing process is more complete, the crystallinity is improved, and the purity of the metal oxide in the film component is greatly improved.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the flow chart of the method for preparing metal oxide film provided by embodiment 1 of the present application;

Fig. 2 is the SEM photograph of the vanadium dioxide thin film that the present invention scheme makes;

Fig. 3 is a curve diagram of the square resistance-temperature change of the vanadium oxide thin film.

Detailed ways

In order to make the purpose, technical solutions and advantages of the application clearer, the technical solutions in the embodiments of the application will be clearly and completely described below in conjunction with the drawings in the embodiments of the application. Obviously, the described embodiments are only Some embodiments of this application are not all embodiments. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

The inventor found after many experiments that the reason for the low purity of the thin film of vanadium dioxide prepared by sputtering in the prior art is mainly that the purity of the thin film of vanadium dioxide is related to the degree of crystallinity, and the preparation process of the prior art mainly Using the one-step method, that is, the film is made by one-step sputtering and one-step annealing. In this process, the film is often difficult to anneal completely, and the overall annealing time is often relatively short, which cannot guarantee the crystallinity and component purity of the vanadium dioxide film. In addition, the one-step method of the prior art must use high-temperature annealing. After the temperature changes, the thermal strain between the substrate and the vanadium dioxide film is too large, which will greatly affect the growth mode of the film and even cause the film to fall off.

Based on the summary of the problems and causes of the prior art, this application proposes an improved method for preparing metal oxide thin films, using a two-step method or even a multi-step method of more than two steps to prepare metal oxide thin films by layered sputtering And step-by-step annealing can make the annealing sufficient, the crystallinity is greatly improved, the metal oxide can obtain a higher and suitable grain size, the orientation degree can be improved, and the purity of the metal oxide film can be improved. In addition, there is no need to use high-temperature annealing like the one-step method of the prior art, so the thermal strain between the substrate and the film is small, the film does not fall off and the growth process is not easily affected.

An embodiment of the present invention provides a method for preparing a metal oxide thin film, comprising: performing at least two sputtering processes on the surface of a substrate in a vacuum reaction chamber to obtain a metal oxide thin film.

Each sputtering process includes sputtering the metal oxide on the surface of the substrate with working temperature by sputtering method, then increasing the temperature of the substrate and performing annealing. Through a large number of experiments, it was found that in the two processes before and after multiple sputtering processes, the substrate operating temperature of the previous sputtering process was lower than that of the subsequent sputtering process, that is, the substrate operating temperature of each sputtering process gradually increased. This helps to further improve the purity of the metal oxide thin film.

Sputtering metal oxide on the surface of the substrate includes: using working gas ions to bombard the metal target, and the sputtered metal ions interact with oxygen to form a metal oxide film on the surface of the substrate. The working gas can be an inert gas such as argon. The flow rate of the working gas introduced into the vacuum reaction chamber is 25-30 sccm. The working temperature of the substrate during sputtering may be 200-400°C. The flow rate of oxygen introduced into the vacuum reaction chamber is 1-1.5 sccm. The target temperature of the annealing process for raising the temperature of the substrate may be 300-400° C., and the annealing time may be 2 hours to 3 hours.

The metal can be vanadium, and the metal oxide can be vanadium dioxide. The sputtering may be magnetron sputtering, specifically DC magnetron sputtering.

The specific implementation of the present invention will be described in detail below by taking vanadium dioxide as an example of the metal oxide.

Example 1

Fig. 1 shows the flow chart of the method for preparing metal oxide film provided by embodiment 1 of the present application, including the following steps:

Step S101: preparing a vanadium dioxide precursor.

The substrate wafer can be transferred to the sputtering vacuum reaction chamber, the substrate can be a silicon nitride substrate, and the size can be 8 inches. The working temperature of the substrate can be controlled at 300°C, and the vacuum degree in the vacuum reaction chamber can be about 5×10 ^-8 mTorr. Next, adjust the sputtering power to 200W, the flow rate of the working gas argon into the reaction chamber to be 28 sccm, the flow rate of oxygen to be 1.2 sccm, the pressure in the reaction chamber to be about 2.5mTorr, and the sputtering time to be 900s. Thus, a vanadium dioxide precursor is obtained.

Step S102: annealing to prepare a vanadium dioxide film.

Rapidly increase the temperature of the substrate to 365° C. and keep it warm for 3 hours to obtain a vanadium dioxide film.

Through steps S101 to S102, the first sputtering process is completed.

Step S103: continue to prepare vanadium dioxide.

On the basis of step S102, continue sputtering, the working temperature of the substrate can be controlled at 300° C., and the vacuum degree in the vacuum reaction chamber can be about 5×10 ⁻⁸ mTorr. Then adjust the sputtering power to 200W, the flow rate of the working gas argon into the reaction chamber is 28sccm, the flow rate of oxygen into the reaction chamber is 1.2sccm, the air pressure in the reaction chamber can be about 2.5mTorr, and the sputtering time is 900s. Thus, vanadium dioxide is obtained.

Step S104: annealing to prepare a vanadium dioxide film.

Rapidly increase the temperature of the substrate to 365° C. and keep it warm for 3 hours to obtain a vanadium dioxide film.

Through steps S101 to S102, the second sputtering process is completed.

In other embodiments of the present application, the holding time of the annealing process in step S103 and step S104 may be replaced with 2 hours. In addition, the time of the sputtering process in step S101 and step S102 can be replaced with 600s.

In addition, in addition to using two sputtering processes as in the above-mentioned embodiment 1, three or more sputtering processes can also be used, and each sputtering process includes sputtering to prepare metal oxides and annealing to prepare metal oxide films . Wherein the annealing temperature of each time except the first time, the subsequent annealing temperature can be kept consistent. For example, in Embodiment 1, a third sputtering annealing process may be added, and the annealing temperature may be 365°.

The preparation method of the embodiment of the present application performs sputtering and annealing step by step, the annealing process is more complete, the crystallinity is improved, and the purity of the metal oxide in the film component is greatly improved.

The embodiment of the present invention also discloses a metal oxide thin film prepared by the above method. Specifically, the metal oxide thin film may be a vanadium dioxide thin film.

As shown in Figure 2, it is the SEM photo of the vanadium dioxide thin film prepared by the scheme of the present invention, the obtained thin film is very uniform and continuous, and shows a high surface coverage. The film annealed at a relatively low temperature shows a flat surface formed by close-packed junctions with well-defined grain boundaries and large grain sizes. This special structure VO2 film exhibits excellent reversible metal-semiconductor phase transition characteristics. As shown in Figure 3, the initial value of the sheet resistance is around 521kΩ/□. In the low temperature range, the sheet resistance of the film gradually decreases with the increase of temperature, showing the characteristics of a semiconductor; the resistance curve near high temperature shows that the sheet resistance decreases. The minor trend slowed down, and the square resistance remained at about 1.8kΩ/□ after the transformation, and the change range of the square resistance before and after high and low temperatures reached 2.5 orders of magnitude.

The above descriptions are only preferred embodiments of the application, and are not intended to limit the application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the application shall be included in the protection of the application. within range.

Claims (10)

1. A method for preparing a metal oxide thin film, comprising: In a vacuum reaction chamber, at least two sputtering processes are performed on the surface of the substrate to obtain a metal oxide film; Each sputtering process includes: using a sputtering method, after sputtering metal oxide on the surface of the substrate with working temperature, increasing the temperature of the substrate and performing annealing to obtain a metal oxide film. 2. The method according to claim 1, wherein the at least two sputtering processes include the first sputtering process and the second sputtering process carried out in sequence, wherein the substrate of the first sputtering process The operating temperature is lower than the operating temperature of the substrate in the second sputtering process. 3. The method according to claim 1, wherein the sputtering metal oxide on the substrate surface comprises: using working gas ions to bombard the metal target, and the sputtered metal ions interact with oxygen to form metal oxide films. 4. The method according to claim 3, wherein the working gas is an inert gas. 5. The method according to claim 1, characterized in that, the working temperature of the substrate during the sputtering process is 200-400°C. 6. The method according to claim 3, characterized in that the flow rate of the working gas introduced into the vacuum reaction chamber is 25-30 sccm. 7. The method according to claim 3, characterized in that the flow rate of oxygen introduced into the vacuum reaction chamber is 1-1.5 sccm. 8. The method according to any one of claims 1 to 7, wherein the metal is vanadium and the metal oxide is vanadium dioxide. 9. The method according to any one of claims 1 to 7, characterized in that the sputtering is DC magnetron sputtering. 10. A metal oxide thin film, characterized in that the oxide thin film is prepared by the method according to any one of claims 1-9.

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