A method for preparing a metal oxide thin film with a stable stoichiometric ratio

Abstract

The application provides a metal oxide thin film preparation method for realizing stable stoichiometric ratio, and belongs to the technical field of nanoscale thin film preparation.The metal oxide thin film is prepared on a pretreated growth substrate by taking a metal oxide radio frequency magnetron sputtering target material as raw material and through a radio frequency magnetron sputtering mode.In the radio frequency magnetron sputtering process, the rotation speed of the growth substrate is 5-300 r / min, the protective gas is argon, the flow rate is 10-80 sccm, and the radio frequency magnetron sputtering power is 20-120 W.Through the adjustment of core parameters such as gas flow rate, cavity internal pressure and radio frequency magnetron sputtering power, the prepared metal oxide thin film has stable stoichiometric ratio, and the thin film has high flatness and uniformity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanoscale thin film preparation, and particularly relates to a method for preparing a metal oxide thin film with a stable stoichiometric ratio. BACKGROUND

[0002] Metal oxide nanoscale thin films have a great influence on the growth of two-dimensional transition metal chalcogenide crystal materials and the construction of two-dimensional devices. CVD process is often used in the growth of two-dimensional transition metal chalcogenide crystal materials, and the most commonly used is one-step CVD process. However, the growth of two-dimensional transition metal chalcogenide materials by one-step CVD process often encounters problems such as difficulty in nucleation and growth of two-dimensional transition metal chalcogenide materials. For example, the growth of two-dimensional MoTe2 crystal thin film is difficult to nucleate and grow in large quantities due to the small difference in electronegativity between Mo and Te chemical elements, which makes it difficult to form bonds and the chemical bonds are weak. The two-step CVD process of growing two-dimensional MoTe2 crystal thin film by pre-depositing Mo source precursor film through high-temperature tellurization reaction becomes a high-efficiency method suitable for the growth of two-dimensional MoTe2 crystal. This is because pre-depositing Mo source precursor on the substrate surface can effectively reduce the energy loss in the transmission process of Mo source, 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 two-step CVD process due to the large lattice deformation of Mo atomic units. The material growth of two-step CVD process by metal molybdenum oxide precursor film with stable molybdenum oxygen element ratio has the characteristics of fast crystal growth rate and high crystal quality in the subsequent reaction of two-step CVD process due to the small lattice deformation of Mo atomic units. Therefore, high-quality control preparation of metal oxide nanoscale thin film with a certain stoichiometric ratio has great significance for the growth of two-dimensional transition metal chalcogenide crystal materials and the construction of two-dimensional devices.

[0003] The current common preparation method of metal oxide nanoscale thin film has the following two kinds: one is to prepare metal oxide thin film by using thermal evaporation of metal oxide solid, which has the characteristics of simple equipment and simple operation process, but the metal oxide thin film prepared by thermal evaporation of metal oxide is not stable at high temperature, resulting in loss of O atom, and cannot form metal oxide thin film with stable stoichiometric ratio. The other is to prepare metal oxide thin film by using metal peroxide film, which mainly uses the oxidation reaction of metal to prepare metal oxide thin film with certain stoichiometric ratio, and has the characteristics of simple operation, but the oxidation time is long and the oxidation effect is unstable, which is not suitable for preparing large-area, high-quality metal oxide thin film with stable stoichiometric ratio. Therefore, the preparation method of high-quality controlled metal oxide thin film with certain stoichiometric ratio needs to be developed, and therefore the present application provides a preparation method of metal oxide thin film with stable stoichiometric ratio. SUMMARY

[0004] To solve the above technical problems, the present application provides a preparation method of metal oxide thin film with stable stoichiometric ratio, which controls the preparation of metal oxide thin film by radio frequency magnetron sputtering, has good flatness, uniformity and stable stoichiometric ratio, and the thickness of metal oxide precursor thin film has good controllability and repeatability. The growth equipment and process flow used in the present application have high industrial compatibility and good economic benefits.

[0005] To achieve the above purpose, the present application provides a preparation method of metal oxide thin film with stable stoichiometric ratio, which uses metal oxide radio frequency magnetron sputtering target material as raw material, and prepares metal oxide thin film on pretreated growth substrate by radio frequency magnetron sputtering, which specifically includes the following steps:

[0006] (1) hydrophilic treatment of the growth substrate to obtain a pretreated growth substrate;

[0007] (2) fixing the metal oxide radio frequency magnetron sputtering target material and the pretreated growth substrate, and then performing vacuum treatment on the internal system of the cavity;

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

[0009] (4) removing the baffle after the deposition rate of radio frequency magnetron sputtering is stable, and depositing on the growth substrate;

[0010] (5) After the end of the radio frequency magnetron sputtering deposition, the growth substrate is first blocked by a baffle, then the radio frequency power supply of the radio frequency magnetron sputtering control system is turned off, the sputtering process of the target material is stopped, then the protection gas is stopped, the plug valve and the front valve are closed, and finally the protection gas is introduced, the chamber is opened and the sample is taken out, that is, the preparation of the metal oxide thin film with stable stoichiometric ratio is realized.

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

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

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

[0014] Further, the protection gas is high-purity argon 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 thin film, and the flow rate of argon will affect the sputtering rate of the target material and the deposition rate of the metal oxide precursor thin film. If the flow rate of argon is too small, the number of sputtering ions is small, and the sputtering ability is weak, if the flow rate of argon is too high, the number of sputtering ions is too large, and the sputtering of oxygen ions is uncontrollable, all of which will lead to imbalance of the stoichiometric ratio of the thin film.

[0016] Further, in step (3), the protection gas is filled into the cavity to make the pressure in the cavity 1.0-2.5Pa.

[0017] If the pressure in the cavity is too low, the ignition cannot be completed, and if the pressure is too high, the average free path of particles is less than the distance between the target and the substrate, it is difficult to deposit, resulting in uneven and non-uniform thin film, and unstable stoichiometric ratio. Further, if the pressure in the magnetron cavity is more than 2.5Pa, the collision probability of metal oxide sputtering particles increases, the probability of breaking M-O bond increases, and the stoichiometric ratio of the metal oxide thin film O:M<0.95x.

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

[0019] The radio frequency power and the thin film deposition rate range ensure the preparation of high-quality thin film. If the power of the radio frequency magnetron sputtering is too small, the ignition cannot be completed, and if the power of the radio frequency magnetron sputtering is too large, the sputtering of oxygen ions is unbalanced, which affects the stoichiometric ratio of the thin film. Further, if the sputtering power is more than 120W, the energy carried by the plasma will be too large and greater than the bond energy of M-O, which will make the stoichiometric ratio of the metal oxide thin film O:M<0.95x.

[0020] The present application controls the core parameters such as gas flow, internal pressure of the cavity, RF magnetron sputtering power, so that the prepared metal oxide thin film has a stable stoichiometric ratio, and the thin film has high flatness and uniformity, and the metal oxide thin film can realize deposition of a large range of thickness from single-layer atomic thickness to multi-layer atomic thickness, thereby obtaining preparation of a large range of controllable thickness of 1-100nm of the metal oxide precursor thin film.

[0021] In addition, the difference between the stoichiometric ratio of the metal oxide thin film deposited by the present application and the stoichiometric ratio of the metal oxide RF magnetron sputtering target used is within the range of (-0.1, 0.1), that is, the present application deposits MO x The stoichiometric ratio of the precursor thin film satisfies M:O=1:(x±y), wherein y∈(0,0.1). In RF magnetron sputtering, the electric field excites the inert gas to ionize to produce positive ions to accelerate and impact the cathode target, exchange momentum with the target material, thereby causing sputtering of the target material. The momentum of the ionized ions is controlled by factors such as gas flow, internal pressure of the cavity, RF magnetron sputtering power, etc. When the momentum of the ionized ions is low, the target material cannot be excited to sputter. When the momentum of the ionized ions is high, the probability of ionization of the target material increases, resulting in unstable stoichiometric ratio of the thin film deposited on the substrate. At the same time, factors such as gas flow, internal pressure of the cavity, etc. hinder the movement of sputtered particles, making the uniformity and flatness of the deposited thin film unstable. Therefore, by controlling the core parameters such as gas flow, internal pressure of the cavity, RF magnetron sputtering power, etc., the prepared metal oxide precursor thin film has a stable stoichiometric ratio, and the thin film has high flatness and uniformity.

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

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

[0024] (2) The equipment and process flow used in the present application have high industrial compatibility, excellent research result transformation ability and good economic benefit. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the present application illustrated in the drawings and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0026] Figure 1 The preparation process of the metal oxide precursor thin film with stable stoichiometric ratio in Example 1 is shown in the schematic diagram.

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

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

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

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

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

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

[0033] Figures 2-7 In the above, A represents Mo 3d XPS fine spectra and B represents O Is XPS fine spectra. DETAILED DESCRIPTION

[0034] Various illustrative embodiments of the present application are now described in detail below. The following description includes specific details for the purpose of providing a thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without these specific details. In other instances, well-known structures and functions have not been described in detail in order to avoid obscuring the understanding of the present application.

[0035] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of a parameter, unless otherwise indicated, each intervening value by each intervening value, as well as any other stated or intervening value in that stated range is encompassed. In addition, any combination of the above values, as well as any other stated or intervening value in that stated range is encompassed. Unless otherwise stated, the above values are not inclusive of the endpoints described.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as those commonly understood by one of ordinary skill in the art to which this application pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In case of conflict between the content of the specification and that of any document incorporated herein by reference, the content of the specification prevails.

[0037] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0038] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" and the like are open-ended terms that are intended to permit but not limit the inclusion of elements or the number of elements, as well as the possibility that one or more elements can be incorporated into the composition, method, or the like.

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

[0040] (1) performing hydrophilic treatment on the 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 performing vacuumizing treatment on the internal system of the cavity;

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

[0043] (4) removing the baffle after the deposition rate of the radio frequency magnetron sputtering is stable, and depositing on the growth substrate;

[0044] (5) after the radio frequency magnetron sputtering deposition is completed, shielding the growth substrate with a baffle, closing the radio frequency power supply of the radio frequency magnetron sputtering control system to stop the sputtering process of the target, then stopping the input of the protective gas, closing the plug valve and the front valve, and finally inputting the protective gas, opening the chamber to take out the sample, thereby realizing the preparation of the metal oxide film with stable stoichiometric ratio.

[0045] In the preferred embodiment of the present application, the metal oxide radio frequency magnetron sputtering target is MO x , wherein 0≤x≤3, and M is a metal element.

[0046] In the preferred embodiment of the present application, the metal oxide RF magnetron sputtering target is MoO2, MoO3 or WO3.

[0047] In the preferred embodiment of the present application, the rotation speed of the growth substrate during RF magnetron sputtering 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 the preferred embodiment of the present application, the protective gas is high-purity argon with a flow rate of 10-80 sccm.

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

[0051] In the preferred embodiment of the present application, in step (3), the protective gas is filled into the cavity to make the pressure in the cavity 1.0-2.5 Pa.

[0052] If the pressure in the cavity is too low, the ignition cannot be completed, and if the pressure is too high, the average free path of particles is less than the distance between the target and the substrate, making it difficult to deposit, resulting in uneven and non-uniform films and unstable stoichiometric ratios. Further, if the pressure in the magnetron cavity exceeds 2.5 Pa, the collision probability of metal oxide sputtering particles increases, leading to an increase in the probability of breaking the M-O bond, resulting in a stoichiometric ratio O:M<0.95x of the metal oxide film.

[0053] In the preferred embodiment of the present application, the RF magnetron sputtering power is 20-120 W.

[0054] The RF power and the film deposition rate range ensure the deposition of high-quality films. If the RF magnetron sputtering power is too small, the ignition cannot be completed, and if the RF magnetron sputtering power is too large, the sputtering of oxygen ions is unbalanced, affecting the stoichiometric ratio of the film. If the sputtering power exceeds 120 W, the energy carried by the plasma will be too large and greater than the M-O bond energy, resulting in a stoichiometric ratio O:M<0.95x of the metal oxide film.

[0055] In the preferred embodiment of the present application, "high-purity argon" refers to argon with a purity of ≥99.999%, and "high-purity N2" refers to N2 with a purity of ≥99.999%.

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

[0057] The technical solutions of the application are further described below through examples.

[0058] Example 1

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

[0060] (1) Put the Si / SiO2 growth substrate into an acetone solution for ultrasonic treatment for 20 min, then soak it in an isopropanol solution for 20 min, and then take it out and dry it with high-purity N2; then put the growth substrate into a plasma etching machine, first pass in 20 sccm O2, etching power is 50 W, etching time is 200 s; after etching, close the O2, pass in 20 sccm Ar, etching power is 40 W, etching time is 300 s, complete the etching and cleaning treatment of the substrate surface, and obtain the pretreated growth substrate;

[0061] (2) Put the high-purity molybdenum trioxide target material and the pretreated growth substrate obtained in step (1) into the designated position of the radio frequency magnetron sputtering system and fix it, then use the mechanical pump and the molecular pump to perform vacuum treatment on the inside of the equipment system cavity, so that the system vacuum degree inside the cavity reaches 3x10 -4 Pa below;

[0062] (3) Fill high-purity argon gas with a flow rate of 50 sccm into the cavity, adjust the molecular pump plug-in valve to make the system gas pressure in the cavity stable at 1.8 Pa, adjust the rotation speed of the growth substrate placed on the turntable to 20 r / min, so that the substrate rotates uniformly in the cavity, then shield the growth substrate with a baffle, and then turn on the radio frequency power supply of the radio frequency magnetron sputtering, adjust the radio frequency magnetron sputtering power to 45 W, so that the deposition rate is stable at

[0063] (4) After the radio frequency magnetron sputtering deposition rate is stable, adjust the radio frequency magnetron sputtering control system to manual control, remove the baffle under the substrate to deposit on the growth substrate, shield the baffle after depositing 5 nm MO3 thin film, and complete the preparation of the MO3 thin film;

[0064] (5) Turn off the RF power of the RF magnetron sputtering control system, stop the sputtering process of the target material, then stop the Ar flow, close the plug-in valve and the front valve, and finally pass Ar to make the internal system pressure of the chamber reach 101 kPa atmospheric pressure, then open the chamber to take out the sample, that is, to realize the preparation of a stable stoichiometric metal oxide thin film (MO3 thin film).

[0065] The full spectrum and C, Mo, and O fine spectrum were scanned by using the ultra-high vacuum ultraviolet photoelectron spectrometer of Thermo Fisher. The spectrum was analyzed by using the avantage software, the charging calibration was performed by using the C1s peak, then the Mo and O were peak-fitted, and the peak-fitting results were plotted by using the oringin software. The relative element ratio of Mo and O was calculated by using the normalization processing model in the avantage software, that is, the Mo / O stoichiometric ratio was obtained. The peak library used is the ALTHERO1 library, and the energy correction model is the TPP-2M IMFP model.

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

[0067] Example 2

[0068] A preparation method of a metal oxide thin film with a stable stoichiometric ratio is specifically as follows:

[0069] (1) Put the sapphire growth substrate into an acetone solution for ultrasonic treatment for 10 min, then soak it in an isopropyl alcohol solution for 10 min, and then take it out and dry it with high-purity N2; then put the growth substrate into a plasma etching machine, first pass in 30 sccm O2, etching power is 50 W, etching time is 200 s; after etching, close the O2, pass in 25 sccm Ar, etching power is 50 W, etching time is 300 s, complete the etching and cleaning treatment of the substrate surface, and obtain a pretreated growth substrate;

[0070] (2) Put the high-purity MoO2 target and the pretreated growth substrate obtained in step (1) into the designated position of the RF magnetron sputtering system and fix them, then use a mechanical pump and a molecular pump to perform vacuum treatment on the internal system of the chamber, so that the internal system vacuum degree of the chamber reaches 3.5×10 -4 Pa below;

[0071] (3) fill high purity argon gas with a flow rate of 40 sccm into the cavity, adjust the molecular pump plug-in valve to stabilize the cavity internal system gas pressure at 2.0 Pa, adjust the rotation speed of the growth substrate placed on the turntable to 25 r / min to make the substrate rotate uniformly in the cavity, then shield the growth substrate with the baffle, and open the radio frequency power supply of the radio frequency magnetron sputtering, adjust the radio frequency magnetron sputtering power to 40 W to stabilize the deposition rate at

[0072] (4) after the deposition rate of the radio frequency magnetron sputtering is stabilized, adjust the radio frequency magnetron sputtering control system to manual control, remove the baffle under the substrate to deposit on the growth substrate, and stabilize the deposition of 4 nm MO2 film, then cover the baffle to complete the preparation of the MO2 film;

[0073] (5) turn off the radio frequency power supply of the radio frequency magnetron sputtering control system to stop the sputtering process of the target material, then stop the argon gas, close the plug-in valve and the front valve, finally, after the argon gas is introduced to make the cavity internal system gas pressure reach 101 kPa atmospheric pressure, open the chamber to take out the sample, that is, to realize the preparation of the MO2 film with a stable stoichiometric ratio.

[0074] The test method is the same as that in Example 1, and 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 of the MO2 film obtained in Example 2 is about 1.97, and the difference between the stoichiometric ratio of the deposited MO2 film and the stoichiometric ratio of the high-purity molybdenum dioxide target used is within the range of (-0.1, 0.1).

[0075] Example 3

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

[0077] (1) put the Si / SiO2 growth substrate into an acetone solution for ultrasonic treatment for 20 min, then soak it in an isopropyl alcohol solution for 20 min, and then take it out and dry it with high-purity N2; then put the growth substrate into a plasma etching machine, first introduce 20 sccm of O2, the etching power is 50 W, and the etching time is 200 s; after etching, close the O2, introduce 20 sccm of Ar, the etching power is 40 W, and the etching time is 300 s, to complete the etching and cleaning treatment of the substrate surface, and obtain a pretreated growth substrate;

[0078] (2) place the high-purity WO3 target material and the pretreated growth substrate obtained in step (1) in the designated position of the radio frequency magnetron sputtering system and fix them, then use a mechanical pump and a molecular pump to perform vacuum treatment on the cavity internal system of the equipment system, so that the cavity internal system vacuum degree reaches 4 × 10 -4 Pa below;

[0079] (3) Fill high purity argon gas with a flow rate of 50 sccm into the cavity, adjust the molecular pump plug-in valve to stabilize the cavity internal system gas pressure at 2.0 Pa, adjust the rotation speed of the growth substrate placed on the turntable to 25 r / min to make the substrate rotate uniformly in the cavity, then shield the growth substrate with the baffle, and open the radio frequency power supply of the radio frequency magnetron sputtering, adjust the radio frequency magnetron sputtering power to 55 W to stabilize the deposition rate at

[0080] (4) After the deposition rate of the radio frequency magnetron sputtering is stabilized, adjust the radio frequency magnetron sputtering control system to manual control, remove the baffle under the substrate to deposit on the growth substrate, and stabilize the deposition of 4 nm MO3 film, then cover the baffle to complete the preparation of the MO3 film;

[0081] (5) Turn off the radio frequency power supply of the radio frequency magnetron sputtering control system to stop the sputtering process of the target material, then stop the Ar input, close the plug-in valve and the front valve, finally input Ar to make the cavity internal system gas pressure reach 101 kPa atmospheric pressure, then open the chamber to take out the sample, that is, to realize the preparation of the MO3 film with stable stoichiometric ratio.

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

[0083] Example 4

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

[0085] (1) Put the sapphire growth substrate into acetone solution for ultrasonic treatment for 10 min, then soak it in isopropyl alcohol solution for 10 min, and then take it out and dry it with high-purity N2; then put the growth substrate into a plasma etching machine, first input 30 sccm O2, etching power is 50 W, etching time is 200 s; after etching, close the O2, input 25 sccm Ar, etching power is 50 W, etching time is 300 s, complete the etching and cleaning treatment of the substrate surface, and obtain the pretreated growth substrate;

[0086] (2) Put the high-purity MoO2 target and the pretreated growth substrate obtained in step (1) into the designated position of the radio frequency magnetron sputtering system and fix them, then use the mechanical pump and the molecular pump to perform vacuum treatment on the cavity inside the equipment system, so that the vacuum degree of the cavity inside the system reaches 3.5×10 -4 Pa or below;

[0087] (3) The high-purity argon gas with a flow rate of 10 sccm is filled into the cavity, the molecular pump plug-in valve is adjusted to stabilize the cavity internal system gas pressure at 2.5 Pa, the rotation speed of the rotation disc on which the growth substrate is placed is adjusted to 300 r / min to rotate the substrate at a constant speed in the cavity, then the growth substrate is shielded by the baffle, the radio frequency power supply of the radio frequency magnetron sputtering is turned on, the radio frequency magnetron sputtering power is adjusted to 20 W to stabilize the deposition rate at

[0088] (4) After the radio frequency magnetron sputtering deposition rate is stabilized, the radio frequency magnetron sputtering control system is adjusted to manual control, the baffle under the substrate is removed to deposit on the growth substrate, the baffle is covered after 7 nm MO2 film is deposited stably to complete the preparation of the MO2 film;

[0089] (5) The radio frequency power supply of the radio frequency magnetron sputtering control system is turned off to stop the sputtering process of the target material, then the Ar is stopped, the plug-in valve and the front stage valve are closed, finally the Ar is introduced to make the cavity internal system gas pressure reach 101 kPa atmospheric pressure, then the chamber is opened to take out the sample, that is, the preparation of the MO2 film with a stable stoichiometric ratio is realized.

[0090] The test method is the same as that in 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 MO2 film prepared 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 rotation disc on which the growth substrate is placed is adjusted to 0 r / min. It is tested that the Mo 3d and O1s XPS fine spectra of the MO2 film in the 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 rotation speed of the substrate rotation disc is 0 or low, the randomness of the collision of the metal oxide already deposited on the substrate is weakened, the probability of repeated collision is increased, and oxygen is an active element, which is easy to escape in the process of repeated collision, thereby causing the chemical element ratio of O and Mo to decrease, and the stable control of the stoichiometric ratio cannot be realized.

[0094] Comparative Example 2

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

[0096] Due to excessive pressure, there are too many ionized ions in the cavity, the average free path of particle movement is reduced, and the sputtering rate is slowed down. Due to too many particles in the cavity, the collision probability of MoO2 sputtering particles is increased, the probability of Mo-O bond breaking is increased, and the probability of oxygen element escaping is increased, so that the O and Mo stoichiometric ratio of the MoO2 thin film is reduced, and the stable regulation and control of the stoichiometric ratio cannot be achieved.

[0097] Comparative Example 3

[0098] The same as Example 2, the only difference is that in step (3), the power of the radio frequency magnetron sputtering is 10 W, and the actual deposition rate is 0. Due to insufficient power, the gas cannot be ignited, that is, sputtering plasma cannot be obtained, and the sputtering power is insufficient, resulting in that the target material cannot be sputtered, and the stable regulation and control of the stoichiometric ratio cannot be achieved.

[0099] Comparative Example 4

[0100] The same as Example 2, the only difference is that in step (3), the power of the radio frequency magnetron sputtering is 125 W, and the actual deposition rate is The Mo 3d and O1s XPS fine spectrum of the MO2 thin film in this comparative example is shown in Figure 6 It can be seen that the chemical element ratio of O and Mo of the MO2 thin film is about 1.46.

[0101] Excessive sputtering power leads to excessive energy carried by plasma, which is greater than the bond energy of Mo-O, resulting in the deposition of Mo and O separately. Since O element is an active element, its deposition efficiency is low in a high-energy environment, which reduces the oxygen content in the deposited thin film, resulting in a decrease in the stoichiometric ratio of the MoO2 thin film, and the stable regulation and control of the stoichiometric ratio cannot be achieved.

[0102] Comparative Example 5

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

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

[0105] The above merely provides the preferred embodiment of the present application, and the protection scope of the present application is not limited thereto. Any modification or replacement within the technical scope disclosed by the present application can be easily conceived by those skilled in the art, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for producing a metal oxide thin film realizing a stable stoichiometric ratio, characterized by, The metal oxide thin film is prepared on a pretreated growth substrate by using a metal oxide radio frequency magnetron sputtering target as raw material and through radio frequency magnetron sputtering; The metal oxide radio frequency magnetron sputtering target is MO x wherein 0 < x ≤ 3, M is a metal element; During the radio frequency magnetron sputtering, the rotation speed of the growth substrate is 5-300 r / min; During the radio frequency magnetron sputtering, the protective gas is argon, and the flow rate is 10-80 sccm; The pressure at the start of the radio frequency magnetron sputtering is 1.0-2.5 Pa; The power of the radio frequency magnetron sputtering is 20-120 W.

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