Preparation method of metal oxide film capable of realizing stable stoichiometric ratio

Abstract

The invention provides a metal oxide film preparation method capable of realizing a stable stoichiometric ratio, and belongs to the technical field of nano-scale film preparation. According to the method, a metal oxide radio frequency magnetron sputtering target material is used as a raw material, the metal oxide thin film is prepared on a pretreated growth substrate in a radio frequency magnetron sputtering mode, and in the radio frequency magnetron sputtering process, the rotating speed of the growth substrate is 5-300 r / min, the shielding gas is argon, the flow is 10-80 sccm, and the power of radio frequency magnetron sputtering is 20-120 W. According to the invention, the prepared metal oxide film has a stable stoichiometric ratio and high flatness and uniformity by regulating and controlling core parameters such as gas flow, internal pressure of the cavity and radio frequency magnetron sputtering power.

Description

Technical Field

[0001] The invention belongs to the technical field of nano-scale film preparation, and in particular relates to a method for preparing a metal oxide film with a stable stoichiometric ratio. Background Art

[0002] Metal oxide nanofilms have a huge impact on the growth of two-dimensional transition metal chalcogenide crystal materials and the construction of two-dimensional devices. CVD processes are often used in the growth of two-dimensional transition metal chalcogenide crystal materials, and the most commonly used one-step CVD process is the one-step CVD process. However, when growing two-dimensional transition metal chalcogenide materials by the one-step CVD process, problems such as the difficulty of nucleation and growth of two-dimensional transition metal chalcogenide materials are often encountered. For example, the growth of two-dimensional MoTe2 crystal films is difficult to nucleate and grow in large quantities due to the small difference in the electronegativity of Mo and Te chemical elements, which makes them difficult to bond and the chemical bonds formed are weak. It is difficult to prepare MoTe2 crystal films by the one-step CVD process. The two-step CVD process of growing two-dimensional MoTe2 crystal films by high-temperature tellurization reaction with a pre-deposited Mo source precursor film has become an efficient method suitable for the growth of two-dimensional MoTe2 crystals. This is because pre-depositing the Mo source precursor on the substrate surface can effectively reduce the energy loss during the Mo source transmission process and promote the nucleation and growth process in the growth of two-dimensional materials. The Mo source precursor film prepared by pure metal molybdenum has the characteristics of slow crystal growth rate and low crystal quality in the subsequent reaction of the two-step CVD process due to the large lattice deformation of the Mo atomic unit. The material growth of the two-step CVD process is realized by the metal molybdenum oxide precursor film with a stable molybdenum-oxygen element ratio. Due to the small lattice deformation of the Mo atomic unit, it has the characteristics of fast crystal growth rate and high crystal quality in the subsequent reaction of the two-step CVD process. Therefore, the high-quality controlled preparation of metal oxide nano-scale films with a certain stoichiometric ratio is of great significance for the growth of two-dimensional transition metal chalcogenide crystal materials and the construction of two-dimensional devices.

[0003] There are two common methods for preparing metal oxide nano-scale films: one is to prepare metal oxide films by thermal evaporation of metal oxide solids. This method has the characteristics of simple equipment and simple operation process. However, the preparation of metal oxide films by thermal evaporation of metal oxides has the disadvantage of being unstable at high temperatures, which causes the loss of O atoms and cannot form metal oxide films with stable stoichiometric ratios. The other is to prepare metal oxide films by peroxide metal films. This method mainly uses the oxidation reaction of metals to prepare metal oxide films with a certain stoichiometric ratio. It has the characteristics of simple operation, but the oxidation time required by this method is long, and the oxidation effect is unstable, so it is not suitable for preparing large-area, high-quality metal oxide films with stable stoichiometric ratios. It can be seen that the preparation method of metal oxide films with a certain stoichiometric ratio with high quality control is in urgent need of development. For this reason, the present invention proposes a preparation method of metal oxide films with a stable stoichiometric ratio. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a method for preparing a metal oxide film with a stable stoichiometric ratio. The present invention controls the preparation of a metal oxide film by radio frequency magnetron sputtering, has good flatness, uniformity and a stable stoichiometric ratio, and the thickness of the metal oxide precursor film has good controllability and repeatability. The growth equipment used in the present invention has a high degree of industrial compatibility with the process flow and has good economic benefits.

[0005] To achieve the above object, the present invention provides a method for preparing a metal oxide thin film with a stable stoichiometric ratio, using a metal oxide radio frequency magnetron sputtering target as a raw material, and preparing the metal oxide thin film on a pretreated growth substrate by radio frequency magnetron sputtering, which specifically includes the following steps:

[0006] (1) performing a hydrophilic treatment on a growth substrate to obtain a pretreated growth substrate;

[0007] (2) fixing the metal oxide radio frequency magnetron sputtering target and the pretreated growth substrate, and then evacuating the internal system of the chamber;

[0008] (3) shielding the growth substrate with a baffle, and then filling the cavity with a protective gas to perform radio frequency magnetron sputtering;

[0009] (4) after the RF magnetron sputtering deposition rate stabilizes, the baffle is removed and deposition is performed on the growth substrate;

[0010] (5) After the RF magnetron sputtering deposition is completed, the growth substrate is first blocked by a baffle, and then the RF power supply of the RF magnetron sputtering control system is turned off to stop the sputtering process of the target material, and then the introduction of the protective gas is stopped, the gate valve and the front stage valve are closed, and finally the protective gas is introduced, the chamber is opened and the sample is taken out, thereby achieving the preparation of a metal oxide film with a stable stoichiometric ratio.

[0011] Furthermore, the metal oxide radio frequency magnetron sputtering target is MO x , where 0≤x≤3, and M is a metal element.

[0012] Furthermore, during the radio frequency magnetron sputtering process, the rotation speed of the growth substrate is 5-300 r / min.

[0013] The rotation speed of the growth substrate affects the uniformity and flatness of the metal oxide precursor film deposition.

[0014] Furthermore, the protective gas is high-purity argon gas with a flow rate of 10-80sccm.

[0015] Argon is an inert gas. The purity of argon will affect the purity of the deposited metal oxide precursor film. The flow rate of argon will affect the rate at which the target material is sputtered and the deposition rate of the metal oxide precursor film. If the argon flow rate is too small, the number of sputtered ions is small and the sputtering ability is weak. If the argon flow rate is too high, the number of sputtered ions is too large and the oxygen ion sputtering is uncontrollable, all of which will lead to an imbalance in the film stoichiometric ratio.

[0016] Furthermore, in step (3), protective gas is filled into the cavity so that the pressure inside the cavity is 1.0-2.5Pa.

[0017] When the pressure inside the cavity is too low, ignition cannot be completed. When the pressure is too high, the mean free path of the particles is less than the distance between the target and the substrate, making it difficult to deposit, resulting in an uneven, non-uniform film and an unstable stoichiometric ratio. Furthermore, when the pressure inside the magnetron cavity exceeds 2.5 Pa, the probability of metal oxide sputtering particles colliding increases, resulting in an increased probability of MO bond breaking, making the stoichiometric ratio of the metal oxide film O:M < 0.95x.

[0018] Furthermore, the power of the radio frequency magnetron sputtering is 20-120W.

[0019] The range of RF power and film deposition rate ensures high-quality film deposition preparation. If the power of RF magnetron sputtering is too small, it cannot complete the ignition. If the power of RF magnetron sputtering is too large, the oxygen ion sputtering will be unbalanced, affecting the stoichiometric ratio of the film. Furthermore, if the sputtering power exceeds 120W, the kinetic energy driven by the plasma will be too large and greater than the MO bond energy, making the stoichiometric ratio of the metal oxide film O:M<0.95x.

[0020] The present invention controls core parameters such as gas flow rate, internal pressure of the cavity, radio frequency magnetron sputtering power, etc., so that the prepared metal oxide film has a stable stoichiometric ratio, and the film has high flatness and uniformity. The metal oxide film can be deposited in a wide range of thicknesses from single-layer atomic thickness to multi-layer atomic thickness, thereby obtaining the preparation of a metal oxide precursor film with a controllable thickness in a wide range of 1-100nm.

[0021] In addition, the difference between the stoichiometric ratio of the metal oxide film deposited and prepared by the present invention and the stoichiometric ratio of the metal oxide radio frequency magnetron sputtering target used is within the range of (-0.1, 0.1), that is, the MO deposited by the present invention is x The stoichiometric ratio of the precursor film satisfies M:O=1:(x±y), where y∈(0,0.1). In radio frequency magnetron sputtering, an electric field is used to excite an inert gas to ionize and generate positive ions that accelerate and impact the cathode target, exchanging momentum with the target material, thereby causing the sputtering of the target material. The momentum of the ionized ions is jointly controlled by factors such as gas flow rate, pressure inside the cavity, and radio frequency magnetron sputtering power. When the momentum of the ionized ions is low, the target material cannot be stimulated to sputter. When the momentum of the ionized ions is high, the probability of ionization of the induced target material increases, resulting in an unstable stoichiometric ratio of the film deposited on the substrate. At the same time, factors such as gas flow rate and pressure inside the cavity hinder the movement of sputtered particles, making the uniformity and flatness of the deposited film unstable. Therefore, the present invention adjusts core parameters such as gas flow rate, pressure inside the cavity, and radio frequency magnetron sputtering power, so that the prepared metal oxide precursor film has a stable stoichiometric ratio, and the film has high flatness and uniformity.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] (1) The metal oxide film prepared by the method of the present invention has good flatness, uniformity and stable stoichiometric ratio, and the thickness of the metal oxide film has good controllability and repeatability.

[0024] (2) The equipment and process flow used in the present invention have a high degree of industrial compatibility, excellent research results transformation capabilities and good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0026] Figure 1 Schematic diagram of the preparation process of the metal oxide precursor film with a stable stoichiometric ratio in Example 1;

[0027] Figure 2 The Mo 3d and O1s XPS fine spectra of the MoO3 film prepared in Example 1, O:Mo=2.94;

[0028] Figure 3 The Mo 3d and O1s XPS fine spectra of the MoO2 film prepared in Example 2, O:Mo=1.97;

[0029] Figure 4 The Mo 3d and O1s XPS fine spectra of the MoO2 film prepared in Comparative Example 1, O:Mo=1.65;

[0030] Figure 5 The Mo 3d and O1s XPS fine spectra of the MoO2 film prepared in Comparative Example 2, O:Mo=1.46<0.95×2;

[0031] Figure 6 The Mo 3d and O1s XPS fine spectra of the MoO2 film prepared in Comparative Example 4, O:Mo=1.50<0.95×2;

[0032] Figure 7 The Mo 3d and O1s XPS fine spectra of the MoO3 film prepared in Comparative Example 5, O:Mo=2.53;

[0033] Figure 2-Figure 7 In the figure, A represents the Mo 3d XPS fine spectrum, and B represents the O1s XPS fine spectrum. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] The embodiment of the present invention provides a method for preparing a metal oxide precursor film with a stable stoichiometric ratio, using a metal oxide radio frequency magnetron sputtering target as a raw material, and preparing the metal oxide precursor film on a pretreated growth substrate by radio frequency magnetron sputtering, which specifically includes the following steps:

[0040] (1) performing a hydrophilic treatment on a growth substrate to obtain a pretreated growth substrate;

[0041] (2) fixing the metal oxide radio frequency magnetron sputtering target and the pretreated growth substrate, and then evacuating the internal system of the chamber;

[0042] (3) shielding the growth substrate with a baffle, and then filling the cavity with a protective gas to perform radio frequency magnetron sputtering;

[0043] (4) after the RF magnetron sputtering deposition rate stabilizes, the baffle is removed and deposition is performed on the growth substrate;

[0044] (5) After the RF magnetron sputtering deposition is completed, the growth substrate is first blocked by a baffle, and then the RF power supply of the RF magnetron sputtering control system is turned off to stop the sputtering process of the target material, and then the introduction of the protective gas is stopped, the gate valve and the front stage valve are closed, and finally the protective gas is introduced, the chamber is opened and the sample is taken out, thereby achieving the preparation of a metal oxide film with a stable stoichiometric ratio.

[0045] In a preferred embodiment of the present invention, the metal oxide RF magnetron sputtering target is MO x , where 0≤x≤3, and M is a metal element.

[0046] In a preferred embodiment of the present invention, the metal oxide radio frequency magnetron sputtering target is MoO2, MoO3 or WO3.

[0047] In a preferred embodiment of the present invention, during the radio frequency magnetron sputtering process, the rotation speed of the growth substrate is 5-300 r / min.

[0048] The rotation speed of the growth substrate affects the uniformity and flatness of the metal oxide film deposition.

[0049] In a preferred embodiment of the present invention, the protective gas is high-purity argon gas with a flow rate of 10-80 sccm.

[0050] Argon is an inert gas. The purity of argon will affect the purity of the deposited metal oxide precursor film. The flow rate of argon will affect the rate at which the target material is sputtered and the deposition rate of the metal oxide precursor film. If the argon flow rate is too small, the number of sputtered ions is small and the sputtering ability is weak. If the argon flow rate is too high, the number of sputtered ions is too large and the oxygen ion sputtering is uncontrollable, all of which will lead to an imbalance in the film stoichiometric ratio.

[0051] In a preferred embodiment of the present invention, in step (3), protective gas is filled into the cavity so that the pressure inside the cavity is 1.0-2.5Pa.

[0052] When the pressure inside the cavity is too low, ignition cannot be completed. When the pressure is too high, the mean free path of the particles is less than the distance between the target and the substrate, making it difficult to deposit, resulting in an uneven, non-uniform film and an unstable stoichiometric ratio. Furthermore, when the pressure inside the magnetron cavity exceeds 2.5 Pa, the probability of metal oxide sputtering particles colliding increases, resulting in an increased probability of MO bond breaking, making the stoichiometric ratio of the metal oxide film O:M < 0.95x.

[0053] In a preferred embodiment of the present invention, the power of the radio frequency magnetron sputtering is 20-120W.

[0054] The range of RF power and film deposition rate ensures high-quality film deposition preparation. If the power of RF magnetron sputtering is too small, it cannot complete the ignition. If the power of RF magnetron sputtering is too large, the oxygen ion sputtering will be unbalanced, affecting the stoichiometric ratio of the film. Sputtering power exceeding 120W will cause the kinetic energy of the plasma to be too large, and greater than the MO bond energy, making the stoichiometric ratio of the metal oxide film O:M<0.95x.

[0055] The “high-purity argon gas” in the embodiment of the present invention refers to argon gas with a purity of ≥99.999%, and the “high-purity N2” refers to N2 with a purity of ≥99.999%.

[0056] All raw materials used in the embodiments of the present invention are purchased commercially, among which the purity of "high-purity molybdenum trioxide target material and high-purity molybdenum dioxide target material" is ≥99.99%, and the purity of "high-purity tungsten trioxide target material" is ≥95%, all of which are purchased from Hebei Yanhe New Material Technology Co., Ltd.

[0057] The technical solution of the present invention is further illustrated by the following embodiments.

[0058] Example 1

[0059] A schematic diagram of the preparation process of a metal oxide film with a stable stoichiometric ratio is shown in Figure 1 , specifically:

[0060] (1) placing the Si / SiO2 growth substrate in an acetone solution for ultrasonic treatment for 20 minutes, then soaking it in an isopropanol solution for 20 minutes, and then taking it out and drying it with high-purity N2; then placing the growth substrate in a plasma etcher, first introducing 20 sccm O2, the etching power is 50 W, and the etching time is 200 s; after the etching is completed, the O2 is turned off, and 20 sccm Ar is introduced, the etching power is 40 W, and the etching time is 300 s, completing the etching and cleaning of the substrate surface to obtain a pretreated growth substrate;

[0061] (2) placing the high-purity molybdenum trioxide target and the pre-treated growth substrate obtained in step (1) at a designated position in the radio frequency magnetron sputtering system and fixing them, and then evacuating the inside of the cavity of the equipment system by using a mechanical pump and a molecular pump to make the vacuum degree of the system inside the cavity reach 3×10 -4 Below Pa;

[0062] (3) High-purity argon gas with a gas flow rate of 50 sccm was filled into the chamber, and the molecular pump plug valve was adjusted to stabilize the system pressure in the chamber at 1.8 Pa. The rotation speed of the turntable on which the growth substrate was placed was adjusted to 20 r / min so that the substrate rotated at a uniform speed in the chamber. Then, the growth substrate was shielded with a baffle, and the RF power supply of the RF magnetron sputtering was turned on. The RF magnetron sputtering power was adjusted to 45 W, so that the deposition rate was stabilized at 200 μm.

[0063] (4) After the RF magnetron sputtering deposition rate is stabilized, the RF magnetron sputtering control system is adjusted to manual control, the baffle under the substrate is removed and deposition is performed on the growth substrate. After a 5 nm MO3 film is stably deposited, the baffle is placed on to complete the preparation of the MO3 film;

[0064] (5) Turn off the RF power supply of the RF magnetron sputtering control system, stop the sputtering process of the target material, then stop the introduction of Ar, close the gate valve and the front valve, and finally introduce Ar to make the system pressure inside the chamber reach 101 kPa atmospheric pressure, then open the chamber and take out the sample, thus achieving the preparation of a metal oxide film (MO3 film) with a stable stoichiometric ratio.

[0065] The test was conducted using the ultra-high vacuum ultraviolet photoelectron spectroscopy measurement equipment of Thermo Fisher Scientific, and the full spectrum and the fine spectra of C, Mo, and O were scanned. The spectrum was analyzed using avantage software, and the C1s peak was used for charge calibration. Then, Mo and O were subjected to peak fitting, and the results of the peak fitting were plotted using oringin software. The relative element ratio of Mo and O was calculated using the normalization processing model provided in the avantag software, and the Mo / O stoichiometric ratio was obtained. The peak library used was the ALTHERO1 library, and the energy correction model was the TPP-2M IMFP model.

[0066] The Mo 3d and O1s XPS fine spectra of the MO3 film in this example are shown in Figure 2 It can be seen that O:Mo=2.94, that is, the chemical element ratio of O and Mo in the MO3 film obtained in Example 1 is about 2.94, and the difference between the stoichiometric ratio of the MO3 film prepared by deposition and the stoichiometric ratio of the high-purity molybdenum trioxide target used is in the range of (-0.1, 0.1).

[0067] Example 2

[0068] A method for preparing a metal oxide film with a stable stoichiometric ratio is specifically as follows:

[0069] (1) placing the sapphire growth substrate in an acetone solution for ultrasonic treatment for 10 minutes, then soaking it in an isopropanol solution for 10 minutes, and then taking it out and drying it with high-purity N2; then placing the growth substrate in a plasma etcher, first introducing 30 sccm O2, the etching power is 50 W, and the etching time is 200 s; after the etching is completed, the O2 is turned off, and 25 sccm Ar is introduced, the etching power is 50 W, and the etching time is 300 s, completing the etching and cleaning of the substrate surface to obtain a pretreated growth substrate;

[0070] (2) The high-purity MoO2 target and the pre-treated growth substrate obtained in step (1) are placed at a designated position in the radio frequency magnetron sputtering system and fixed, and then the inside of the cavity of the equipment system is evacuated by a mechanical pump and a molecular pump to make the vacuum degree of the system inside the cavity reach 3.5×10 -4 Below Pa;

[0071] (3) High-purity argon gas with a gas flow rate of 40 sccm was filled into the chamber, and the molecular pump gate valve was adjusted to stabilize the system pressure in the chamber at 2.0 Pa. The rotation speed of the turntable on which the growth substrate was placed was adjusted to 25 r / min so that the substrate rotated at a uniform speed in the chamber. Then, the growth substrate was shielded with a baffle, and the RF power supply of the RF magnetron sputtering was turned on. The RF magnetron sputtering power was adjusted to 40 W so that the deposition rate was stabilized at 2.0 Pa.

[0072] (4) After the RF magnetron sputtering deposition rate is stabilized, the RF magnetron sputtering control system is adjusted to manual control, the baffle under the substrate is removed and deposition is performed on the growth substrate. After a 4 nm MO2 film is stably deposited, the baffle is placed on to complete the preparation of the MO2 film;

[0073] (5) Turn off the RF power supply of the RF magnetron sputtering control system, stop the sputtering process of the target material, then stop the introduction of Ar, close the gate valve and the front valve, and finally introduce Ar to make the system pressure inside the chamber reach 101 kPa atmospheric pressure, then open the chamber and take out the sample, thus achieving the preparation of MO2 thin film with a stable stoichiometric ratio.

[0074] The test method is the same as in Example 1. The Mo 3d and O1s XPS fine spectra of the MO2 film in this example are shown in Figure 3 It can be seen that O:Mo=1.97, that is, the chemical element ratio of O and Mo in the MO2 film obtained in Example 2 is about 1.97, and the difference between the stoichiometric ratio of the MO2 film prepared by deposition and the stoichiometric ratio of the high-purity molybdenum dioxide target used is in the range of (-0.1, 0.1).

[0075] Example 3

[0076] A method for preparing a metal oxide film with a stable stoichiometric ratio is specifically as follows:

[0077] (1) placing the Si / SiO2 growth substrate in an acetone solution for ultrasonic treatment for 20 minutes, then soaking it in an isopropanol solution for 20 minutes, and then taking it out and drying it with high-purity N2; then placing the growth substrate in a plasma etcher, first introducing 20 sccm O2, the etching power is 50 W, and the etching time is 200 s; after the etching is completed, the O2 is turned off, and 20 sccm Ar is introduced, the etching power is 40 W, and the etching time is 300 s, completing the etching and cleaning of the substrate surface to obtain a pretreated growth substrate;

[0078] (2) The high-purity WO3 target material and the pre-treated growth substrate obtained in step (1) are placed at a designated position in the RF magnetron sputtering system and fixed, and then the inside of the cavity of the equipment system is evacuated using a mechanical pump and a molecular pump to make the vacuum degree of the system inside the cavity reach 4×10 -4 Below Pa;

[0079] (3) High-purity argon gas with a gas flow rate of 50 sccm was filled into the chamber, and the molecular pump gate valve was adjusted to stabilize the system pressure in the chamber at 2.0 Pa. The rotation speed of the turntable on which the growth substrate was placed was adjusted to 25 r / min so that the substrate rotated at a uniform speed in the chamber. Then, the growth substrate was shielded with a baffle, and the RF power supply of the RF magnetron sputtering was turned on. The RF magnetron sputtering power was adjusted to 55 W, so that the deposition rate was stabilized at 2.0 Pa.

[0080] (4) After the RF magnetron sputtering deposition rate is stabilized, the RF magnetron sputtering control system is adjusted to manual control, the baffle under the substrate is removed and deposition is performed on the growth substrate. After a 4 nm MO3 film is stably deposited, the baffle is placed on to complete the preparation of the MO3 film;

[0081] (5) Turn off the RF power supply of the RF magnetron sputtering control system, stop the sputtering process of the target material, then stop the introduction of Ar, close the gate valve and the front valve, and finally introduce Ar to make the system pressure inside the chamber reach 101 kPa atmospheric pressure, then open the chamber and take out the sample, thus achieving the preparation of MO3 thin film with a stable stoichiometric ratio.

[0082] The testing method is the same as that in Example 1. The chemical element ratio of O and W in the MO3 film obtained in Example 3 is close to 3:1. The difference between the stoichiometric ratio of the MO3 film prepared by deposition and the stoichiometric ratio of the high-purity tungsten trioxide target used is in the range of (-0.1, 0.1), and the surface of the prepared MO3 film has high flatness and good uniformity.

[0083] Example 4

[0084] A method for preparing a metal oxide film with a stable stoichiometric ratio is specifically as follows:

[0085] (1) placing the sapphire growth substrate in an acetone solution for ultrasonic treatment for 10 minutes, then soaking it in an isopropanol solution for 10 minutes, and then taking it out and drying it with high-purity N2; then placing the growth substrate in a plasma etcher, first introducing 30 sccm O2, the etching power is 50 W, and the etching time is 200 s; after the etching is completed, the O2 is turned off, and 25 sccm Ar is introduced, the etching power is 50 W, and the etching time is 300 s, completing the etching and cleaning of the substrate surface to obtain a pretreated growth substrate;

[0086] (2) The high-purity MoO2 target and the pre-treated growth substrate obtained in step (1) are placed at a designated position in the radio frequency magnetron sputtering system and fixed, and then the inside of the cavity of the equipment system is evacuated by a mechanical pump and a molecular pump to make the vacuum degree of the system inside the cavity reach 3.5×10 -4 Below Pa;

[0087] (3) High-purity argon gas with a gas flow rate of 10 sccm was filled into the chamber, and the molecular pump gate valve was adjusted to stabilize the system pressure in the chamber at 2.5 Pa. The rotation speed of the turntable on which the growth substrate was placed was adjusted to 300 r / min, so that the substrate rotated at a uniform speed in the chamber. Then, the growth substrate was shielded with a baffle, and the RF power supply of the RF magnetron sputtering was turned on. The RF magnetron sputtering power was adjusted to 20 W, so that the deposition rate was stabilized at 200 r / min.

[0088] (4) After the RF magnetron sputtering deposition rate is stabilized, the RF magnetron sputtering control system is adjusted to manual control, the baffle under the substrate is removed and deposition is performed on the growth substrate. After the 7 nm MO2 film is stably deposited, the baffle is placed on to complete the preparation of the MO2 film;

[0089] (5) Turn off the RF power supply of the RF magnetron sputtering control system, stop the sputtering process of the target material, then stop the introduction of Ar, close the gate valve and the front valve, and finally introduce Ar to make the system pressure inside the chamber reach 101 kPa atmospheric pressure, then open the chamber and take out the sample, thus achieving the preparation of MO2 thin film with a stable stoichiometric ratio.

[0090] The test method is the same as that of Example 1. The difference between the stoichiometric ratio of the MO2 film obtained in Example 4 and the stoichiometric ratio of the high-purity tungsten trioxide target used is within the range of (-0.1, 0.1), and the prepared MO2 film has high surface flatness and good uniformity.

[0091] Comparative Example 1

[0092] The same as Example 2, the only difference is that the rotation speed of the turntable on which the growth substrate is placed is adjusted to 0 r / min. After testing, the Mo 3d and O1s XPS fine spectra of the MO2 film in this comparative example are shown in Figure 4 , it can be seen that the chemical element ratio of O and Mo in the obtained MO2 film is about 1.65.

[0093] When the substrate turntable speed is 0 or low, the randomness of the collision of the metal oxides deposited on the substrate is weakened, the probability of repeated collisions increases, and oxygen is an active element. During the repeated collisions, oxygen is easy to escape, resulting in a decrease in the chemical element ratio of O and Mo, and the stable regulation of the stoichiometric ratio cannot be achieved.

[0094] Comparative Example 2

[0095] The same as Example 2, except that in step (3), the protective gas is filled into the cavity to make the pressure inside the cavity 2.6Pa, and the actual deposition rate is The Mo 3d and O1s XPS fine spectra of the MO2 film in this comparative example are shown in Figure 5, it can be seen that the chemical element ratio of O and Mo in the obtained MO2 film is about 1.46.

[0096] Due to the high pressure, there are more ionized ions in the cavity, the mean free path of particle movement is reduced, and the sputtering rate is slowed down. Due to the excessive number of particles in the cavity, the probability of MoO2 sputtering particle collision increases, the probability of Mo-O bond breaking increases, and the probability of oxygen element escape increases, which reduces the O and Mo stoichiometric ratio of MoO2 film and cannot achieve stable regulation of the stoichiometric ratio.

[0097] Comparative Example 3

[0098] The same as Example 2, except that in step (3), the power of the RF magnetron sputtering is 10 W, and the actual deposition rate is 0. Due to insufficient power, the gas cannot be ignited, that is, the sputtering plasma cannot be obtained, and the sputtering power is insufficient, resulting in the inability to sputter the target material, and the inability to achieve stable regulation of the stoichiometric ratio.

[0099] Comparative Example 4

[0100] Same as Example 2, except that in step (3), the power of RF magnetron sputtering is 125 W and the actual deposition rate is The Mo 3d and O1s XPS fine spectra of the MO2 film in this comparative example are shown in Figure 6 , it can be seen that the chemical element ratio of O and Mo in the obtained MO2 film is about 1.50.

[0101] Excessive sputtering power will cause the kinetic energy of the plasma to be too large, which is greater than the Mo-O bond energy, resulting in the separate deposition of Mo and O. Since the O element is an active element, its deposition efficiency is low in a high-energy environment, which reduces the oxygen content in the deposited film, resulting in a decrease in the stoichiometric ratio of the MoO2 film, and the inability to achieve stable regulation of the stoichiometric ratio.

[0102] Comparative Example 5

[0103] The operation steps are consistent with those in Example 1, except that the magnetron sputtering method is changed to the thermal evaporation method, and MoO3 powder (purity ≥ 99.5%, material supplier: MACKLIN) is evaporated onto the substrate surface by a thermal evaporation device (equipment model: PVD 100). The Mo 3d and O1s XPS fine spectra of the MO3 film in this comparative example are shown in FIG. Figure 7 It can be seen that the chemical element ratio of O and Mo in the obtained MO3 film is about 2.53.

[0104] The method of thermal evaporation deposition of MoO3 thin film needs to be prepared in a high-temperature environment, and high temperature easily causes the loss of oxygen elements. Therefore, the O and Mo elements in the obtained MoO3 thin film are less than the standard chemical element stoichiometric ratio, and the stable regulation of the stoichiometric ratio cannot be achieved.

[0105] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a metal oxide thin film with a stable stoichiometric ratio, characterized in that: The metal oxide radio frequency magnetron sputtering target is used as a raw material, and a metal oxide film is prepared on a pretreated growth substrate by radio frequency magnetron sputtering.

2. The method for preparing a metal oxide thin film with a stable stoichiometric ratio according to claim 1, characterized in that: The metal oxide radio frequency magnetron sputtering target is MO x , where 0≤x≤3, and M is a metal element.

3. The method for preparing a metal oxide thin film with a stable stoichiometric ratio according to claim 1, characterized in that: During the radio frequency magnetron sputtering process, the rotation speed of the growth substrate is 5-300 r / min.

4. The method for preparing a metal oxide thin film with a stable stoichiometric ratio according to claim 1, characterized in that: The protective gas during the RF magnetron sputtering process is argon with a flow rate of 10-80sccm.

5. The method for preparing a metal oxide thin film with a stable stoichiometric ratio according to claim 1, characterized in that: The pressure at the beginning of the radio frequency magnetron sputtering is 1.0-2.5 Pa.

6. The method for preparing a metal oxide thin film with a stable stoichiometric ratio according to claim 1, characterized in that: The power of the radio frequency magnetron sputtering is 20-120W.

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