Tungsten-containing oxide and silicon-containing nitride gradient film and preparation method thereof

Abstract

The invention discloses a preparation method of a gradient film containing tungsten oxide and silicon nitride. The method comprises the following steps: selecting a substrate and cleaning the substrate; vacuumizing to basic vacuum, introducing high-purity argon and oxygen, starting to sputter a tungsten target, and depositing a uniform tungsten oxide layer; the titanium target is sputtered at low frequency, meanwhile, the sputtering frequency of the tungsten target is gradually reduced, when the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the highest value, nitrogen is started to be introduced, the silicon target is sputtered at low frequency, the sputtering frequency of the silicon target is gradually increased, and the sputtering frequency of the titanium target is gradually reduced; when the sputtering frequency of the titanium target is reduced to 0, the sputtering frequency of the silicon target reaches the highest value, and independent sputtering of the silicon target is carried out; and annealing and polishing the gradient film. The titanium element is added, so that the gradient film is of a three-element structure, the strength of the gradient film can be effectively enhanced, and the overall quality of the gradient film is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gradient films, and specifically, to a tungsten oxide-containing and silicon nitride-containing gradient film and a preparation method thereof. Background Art

[0002] In the research and application of materials, as a material with special properties, gradient films have broad application prospects in many fields such as optoelectronic devices, aerospace, etc. However, there are some problems to be solved urgently in the existing gradient film preparation technologies and related materials.

[0003] Firstly, in terms of the film structure stability and interface bonding force, the structure stability of conventional gradient films is poor, and the interface bonding force between layers is insufficient, resulting in the phenomenon of film cracking or peeling easily occurring during actual use. This not only affects the service life of the gradient film but also limits its application in some fields with high requirements for structure stability; secondly, the thermal stability problem is also relatively prominent. In a high-temperature environment, the performance of the intermediate layer of the gradient film is prone to degradation, which makes it difficult for the gradient film to maintain good performance under high-temperature working conditions and further narrows its applicable range; furthermore, the material structure stability and optical and electrical properties also need to be improved. Traditional preparation methods are difficult to achieve a smooth transition between layers, the connection between layers is abrupt, stress concentration is likely to occur, and then problems such as cracks and peeling of the material will occur. Moreover, this structural deficiency also affects the optical and electrical properties of the material. In the application of optoelectronic devices, it is impossible to efficiently achieve the transmission and conversion of light and the smooth migration of electrons, limiting the improvement of the overall performance of the device; in addition, the film thickness uniformity of the gradient film is also a key issue. The existing dual-target sputtering technology is difficult to precisely control the film thickness distribution, resulting in a large difference in film thickness at different positions of the gradient film, affecting the consistency of the overall quality and performance of the gradient film.

[0004] For the problems in the related technology, no effective solution has been proposed yet. Summary of the Invention

[0005] For the problems in the related technology, the present invention proposes a tungsten oxide-containing and silicon nitride-containing gradient film and a preparation method thereof to overcome the above-mentioned technical problems existing in the existing related technology.

[0006] Therefore, the specific technical solution adopted by the present invention is as follows:

[0007] A preparation method of a tungsten oxide-containing and silicon nitride-containing gradient film, the method comprising the following steps: S1. Select a substrate and clean the substrate;

[0008] S2. Evacuate to a basic vacuum, introduce high-purity argon and oxygen, and start sputtering a tungsten target to deposit a uniform tungsten oxide layer;

[0009] S3. Sputter the titanium target at a low frequency while gradually reducing the sputtering frequency of the tungsten target. When the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the highest value, and then introduce nitrogen gas and sputter the silicon target at a low frequency. The sputtering frequency of the silicon target gradually increases while the sputtering frequency of the titanium target begins to gradually decrease.

[0010] S4. When the sputtering frequency of the titanium target drops to 0, the sputtering frequency of the silicon target reaches the highest value, and then perform single sputtering of the silicon target.

[0011] S5. Anneal and polish the gradient film.

[0012] As a preferred embodiment, the steps of evacuating to the base vacuum, introducing high-purity argon gas and oxygen gas, and starting to sputter the tungsten target to deposit a uniform tungsten oxide layer include the following:

[0013] S21. Turn on the mechanical pump or molecular pump and start evacuating the deposition chamber.

[0014] S22. Introduce high-purity argon gas and oxygen gas into the deposition chamber.

[0015] S23. Rotate the substrate, start the magnetron sputtering power supply, apply a voltage to the tungsten target to generate plasma. Tungsten atoms are sputtered from the tungsten target, react with the oxygen gas in the deposition chamber to form tungsten oxide, and deposit on the surface of the substrate to form a uniform tungsten oxide thin film.

[0016] As a preferred embodiment, the steps of sputtering the titanium target at a low frequency while gradually reducing the sputtering frequency of the tungsten target. When the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the highest value, and then introduce nitrogen gas and sputter the silicon target at a low frequency. The sputtering frequency of the silicon target gradually increases while the sputtering frequency of the titanium target begins to gradually decrease include the following:

[0017] S31. Turn on the revolution of the substrate, at the same time start sputtering the titanium target at a low frequency and gradually reduce the sputtering frequency of the tungsten target. When the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the highest value.

[0018] S32. Introduce nitrogen gas and start sputtering the silicon target at a low frequency. The sputtering frequency of the silicon target gradually increases while the sputtering frequency of the titanium target begins to gradually decrease.

[0019] S33. When the substrate is revolving, monitor the frequency change of the quartz crystal to obtain the deposited film thickness, thereby determine the film thickness distribution on the rotation radius, obtain the film thickness distribution on the substrate after single-target sputtering, and obtain the revolution speed curve and revolution speed data of the substrate according to the film thickness distribution.

[0020] As a preferred embodiment, when the substrate revolves, the frequency change of the quartz crystal is monitored to obtain the deposited film thickness, so as to determine the film thickness distribution on the rotation radius, obtain the film thickness distribution on the substrate after single-target sputtering, and obtain the revolution speed curve and revolution speed data of the substrate according to the film thickness distribution, including the following steps:

[0021] S331. Establish a formula related to the revolution speed according to the film thickness data. The specific formula is:

[0022] T(r) = A∑V(r)τ(ω, r);

[0023] Among them, r represents the distance from a point on the same plane of the target sputtering area to the center of the plane area; ω represents the revolution speed; τ represents the residence time of a certain point on the substrate in space; V represents the deposition rate distribution in the space above the target, and A is the sputtering constant;

[0024] The sputtering constant is obtained according to the measured film thickness data, deposition time and film thickness distribution model.

[0025] S332. When the revolution speed is ω1, the film thickness of any point on the substrate can be expressed as:

[0026] T1(r) = A∑V(r)τ1(ω, r) = A∑V(r) / ω1;

[0027] When the revolution speed changes from ω1 to xω1, the residence time of the substrate in space changes to τ / x, and the corresponding film thickness can be expressed as:

[0028]

[0029] T2(r) and T1(r) respectively represent the film thicknesses at the revolution rates of xω1 and ω1, τ2(ω, r) and τ1(ω, r) respectively represent the residence times of the substrate at the position r at the revolution rates of xω1 and ω1, and x is the multiple of the change in the revolution rate;

[0030] Divide the angle swept by the substrate above the target into n equal parts, and record the rotation speed of the jth equal part as ω j , then the thickness of a certain point on the rotation radius of the substrate can be expressed as:

[0031]

[0032] Among them, T(r) is, θ is the revolution angle, D(x T , y T ), is the sputtering yield distribution, M is the shielding factor, and M = 0 is taken when the shielding is caused by the cover plate, baffle or the curved edge of the substrate itself of the target, and M = 1 is taken when there is no shielding; cos kα is the angular distribution function of sputtered particles; β is the angle between the incident direction and the normal direction of the substrate when the sputtered material is deposited on the substrate; ρ is the distance from point T on the target to point S on the substrate, and dA r is a certain surface element on the target;

[0033] A series of discrete points {r i} are selected on the rotation radius, and the corresponding discrete film thickness distribution is {T i}:

[0034]

[0035] where r i represents the i-th position on the substrate. To determine the film thickness distribution on the rotation radius, given the distribution characteristic parameters of the magnetron sputtering source and the shape of the substrate, the required revolution speed control curve and revolution speed are obtained through the inversion formula, and the revolution speed of the substrate is controlled using the revolution speed.

[0036] As a preferred embodiment, when the sputtering frequency of the titanium target drops to 0, the sputtering frequency of the silicon target reaches the highest value, and the separate sputtering of the silicon target includes the following steps:

[0037] S41. When the sputtering frequency of the titanium target drops to 0, stop the revolution of the substrate;

[0038] S42. The substrate continues to rotate and the silicon target is sputtered;

[0039] S43. When the required film thickness is reached, stop sputtering.

[0040] A tungsten oxide and silicon nitride gradient film is prepared according to the above preparation method.

[0041] As a preferred embodiment, the raw materials for making this gradient film include a substrate, a tungsten target, a silicon target, a titanium target, oxygen, argon, and nitrogen, and the substrate is made of alloy steel;

[0042] The production process of the titanium target includes the following steps:

[0043] Select nano-titanium dioxide particles with a size of 10 - 100 and a binder, and dissolve the binder in ethanol; mix the nano-titanium dioxide particles with a dispersant and perform ultrasonic dispersion in a solvent, with the ultrasonic time set to 10 - 30 minutes; slowly add the dissolved binder solution to the well-dispersed titanium dioxide slurry and stir evenly; remove the solvent from the slurry by drying to form a powder, and finally press the powder into a target.

[0044] The beneficial effects of the present invention are:

[0045] 1. The present invention forms a ternary gradient film by adding titanium elements to the gradient film, making the structure of the entire gradient film more stable and enhancing the interfacial bonding force. In addition, the ductility and plasticity of titanium elements can absorb mechanical stress, reducing the risk of film cracking or peeling. Moreover, nano-titanium dioxide particles are added between the titanium targets, which can significantly improve the thermal stability of the intermediate layer and prevent performance degradation at high temperatures.

[0046] 2. The present invention enables a smooth transition of the tungsten oxide layer, titanium dioxide layer, and silicon nitride layer by gradually increasing and then gradually decreasing the sputtering of the titanium target, thereby effectively enhancing the stability of the material structure, avoiding stress concentration caused by abrupt connection between layers, reducing the risk of problems such as cracks and peeling in the material, and also optimizing the optical and electrical properties of the material. In some optoelectronic devices, it can make the transmission and conversion of light more efficient and the electron migration smoother, thus improving the overall performance of the device. At the same time, the smooth transition is also beneficial to improving the surface flatness of the material, thereby enhancing the overall quality of the gradient film.

[0047] 3. The present invention determines the deposited film thickness by monitoring the frequency change of a quartz crystal, thereby determining the film thickness distribution on the rotation radius and obtaining the film thickness distribution on the substrate after single-target sputtering. Finally, based on the film thickness distribution, the revolution speed curve and revolution speed data of the substrate are obtained, which can effectively improve the uniformity of the gradient film. After establishing the formulas for the relationship between film thickness data and revolution speed data, and the relationship between rotation speed and film thickness, the revolution speed adjustment curve and revolution rate can be obtained. By using this revolution rate, the uniformity of the gradient film can be effectively improved. At positions with a thicker film thickness, the revolution speed decreases and the deposition time decreases; at positions with a thinner film thickness, the revolution speed increases and the deposition time increases. By changing the residence time of the substrate at different positions in the sputtering area in this way, the periodic thickness of the thin film at different positions of the substrate can be changed, thereby realizing the control of the film layer thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 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 drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0049] Figure 1 is a flowchart of a method for preparing a tungsten oxide-containing and silicon nitride-containing gradient film according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0050] To further illustrate the embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be combined with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0051] According to an embodiment of the present invention, a tungsten oxide-containing and silicon nitride-containing gradient film and a preparation method thereof are provided.

[0052] Now, the present invention will be further described in conjunction with the accompanying drawings and specific embodiments. As Figure 1 shown, a preparation method of a tungsten oxide-containing and silicon nitride-containing gradient film according to an embodiment of the present invention includes the following steps:

[0053] S1. Select a substrate and clean the substrate;

[0054] S2. Evacuate to a base vacuum, introduce high-purity argon and oxygen, and start sputtering a tungsten target to deposit a uniform tungsten oxide layer;

[0055] Further, the step of evacuating to a base vacuum, introducing high-purity argon and oxygen, and starting to sputter a tungsten target to deposit a uniform tungsten oxide layer includes the following steps:

[0056] S21. Turn on a mechanical pump or a molecular pump and start evacuating the deposition chamber;

[0057] S22. Introduce high-purity argon and oxygen into the deposition chamber;

[0058] S23. Rotate the substrate, start the magnetron sputtering power supply, apply a voltage to the tungsten target to generate plasma, sputter tungsten atoms from the tungsten target, react with oxygen in the deposition chamber to form tungsten oxide, and deposit on the surface of the substrate to form a uniform tungsten oxide thin film.

[0059] S3. Sputter a titanium target at a low frequency, and gradually reduce the sputtering frequency of the tungsten target. When the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the highest value, and start introducing nitrogen, sputter a silicon target at a low frequency, the sputtering frequency of the silicon target gradually increases, and the sputtering frequency of the titanium target starts to gradually decrease;

[0060] Further, the step of sputtering a titanium target at a low frequency, gradually reducing the sputtering frequency of the tungsten target, when the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the highest value, and start introducing nitrogen, sputtering a silicon target at a low frequency, the sputtering frequency of the silicon target gradually increases, and the sputtering frequency of the titanium target starts to gradually decrease includes the following steps:

[0061] S31. Start the revolution of the substrate, and at the same time, start the sputtering of the titanium target at a low frequency, and gradually reduce the sputtering frequency of the tungsten target. When the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the highest value.

[0062] S32. Introduce nitrogen gas and start sputtering the silicon target at a low frequency. The sputtering frequency of the silicon target gradually increases, and the sputtering frequency of the titanium target begins to gradually decrease.

[0063] S33. When the substrate is revolving, monitor the frequency change of the quartz crystal to obtain the deposited film thickness, so as to determine the film thickness distribution on the rotation radius, obtain the film thickness distribution on the substrate after single-target sputtering, and obtain the revolution speed curve and revolution speed data of the substrate according to the film thickness distribution.

[0064] Further, when the substrate is revolving, monitoring the frequency change of the quartz crystal to obtain the deposited film thickness, so as to determine the film thickness distribution on the rotation radius, obtain the film thickness distribution on the substrate after single-target sputtering, and obtaining the revolution speed curve and revolution speed data of the substrate according to the film thickness distribution includes the following steps:

[0065] S331. Establish a formula related to the revolution speed according to the film thickness data. The specific formula is:

[0066] T(r) = A∑V(r)τ(ω, r);

[0067] Among them, r represents the distance from a point on the same plane of the target sputtering area to the center of the plane area; ω represents the revolution speed; τ represents the residence time of a certain point on the substrate in space; V represents the deposition rate distribution in the space above the target, and A is the sputtering constant.

[0068] It should be noted that when the substrate rotates to directly above the target, since the target is not infinitely large, the deposition rate V(r) at different distances r from the center on the substrate is not exactly the same. However, since parameters such as sputtering power and working gas pressure have been determined, the V distribution can be regarded as a constant value that does not change with time within the measurement error range. Therefore, to ensure the same thickness at different positions, the revolution speed of the sample holder can be changed to change the deposition time τ.

[0069] S332. When the revolution speed is ω1, the film thickness of any point on the substrate can be expressed as:

[0070] T1(r) = A∑V(r)τ1(ω, r) = A∑V(r) / ω1;

[0071] When the revolution speed changes from ω1 to xω1, the residence time of the substrate in space changes to τ / x, and the corresponding film thickness can be expressed as:

[0072]

[0073] T2(r) and T1(r) represent the film thicknesses at the revolution rates of xω1 and ω1 respectively, τ2(ω, r) and τ1(ω, r) represent the residence times of the substrate at position r at the revolution rates of xω1 and ω1 respectively, and x is the multiple of the change in the revolution rate;

[0074] The angle at which the substrate sweeps over the target is divided into n equal parts, and the rotational speed of the j-th equal part is denoted as ω j , then the thickness at a certain point on the rotational radius of the substrate can be expressed as:

[0075]

[0076] where T(r) is, θ is the revolution angle, D(x T , y T ), is the sputtering yield distribution, M is the shielding factor, M = 0 is taken when the shielding is caused by the cover plate, baffle or the curved edge of the substrate itself of the target, and M = 1 is taken when there is no shielding; cos k α is the angular distribution function of sputtered particles; β is the angle between the incident direction and the normal direction of the substrate when the sputtered material is deposited on the substrate; ρ is the distance from point T on the target to point S on the substrate, and dA r is a certain surface element on the target;

[0077] A series of discrete points {r i} are selected on the rotational radius, and the corresponding discrete film thickness distribution is {T i}:

[0078]

[0079] where r i represents the i-th position on the substrate. To determine the film thickness distribution on the rotational radius, given the distribution characteristic parameters of the magnetron sputtering source and the shape of the substrate, the required revolution speed control curve and revolution rate are obtained by the inversion formula, and the revolution rate of the substrate is controlled using the revolution rate.

[0080] S4. When the sputtering frequency of the titanium target drops to 0, the sputtering frequency of the silicon target reaches the highest value, and the silicon target is sputtered alone;

[0081] Furthermore, the step of when the sputtering frequency of the titanium target drops to 0, the sputtering frequency of the silicon target reaches the highest value, and the silicon target is sputtered alone includes the following steps:

[0082] S41. When the sputtering frequency of the titanium target drops to 0, stop the revolution of the substrate;

[0083] S42. The substrate continues to rotate and the silicon target is sputtered;

[0084] S43. When the required film thickness is reached, stop sputtering.

[0085] S5. Anneal and polish the gradient film.

[0086] It should be noted that annealing and polishing are important steps in the fabrication of the gradient film. Annealing the deposited film enables the atoms to rearrange, further optimizing the crystal structure of the film, enhancing its structural and thermal stability. Polishing, on the other hand, can effectively improve the surface flatness of the film and reduce the surface roughness. This not only helps to improve the optical transmittance of the film, allowing for smoother light transmission, but also, in application scenarios such as optoelectronic devices, avoids local defects caused by surface unevenness, thus comprehensively enhancing the overall quality and performance of the tungsten oxide and silicon nitride-containing gradient film.

[0087] A tungsten oxide and silicon nitride-containing gradient film is prepared according to the above preparation method.

[0088] Furthermore, the raw materials for fabricating this gradient film include a substrate, a tungsten target, a silicon target, a titanium target, oxygen, argon, and nitrogen, and the substrate is made of alloy steel.

[0089] The fabrication process of the titanium target includes the following steps:

[0090] Select nanosized titanium dioxide particles with a size of 10 - 100 and a binder, and dissolve the binder in ethanol; mix the nanosized titanium dioxide particles with a dispersant and perform ultrasonic dispersion in a solvent, with the ultrasonic time set to 10 - 30 minutes; slowly add the dissolved binder solution to the well-dispersed titanium dioxide slurry and stir evenly; remove the solvent from the slurry by drying to form a powder, and finally press the powder into a target.

[0091] It should be noted that in the existing tungsten oxide and silicon nitride system, adding a third element Ti to form a ternary gradient film can make the structure of the film more stable. The chemical activity of Ti enables it to form strong chemical bonds with the tungsten oxide layer and the silicon nitride layer, enhancing the interlayer bonding force. Moreover, the Ti target contains titanium dioxide nanoparticles. Adding titanium dioxide nanoparticles to the Ti intermediate layer can adjust the optical properties of the film and optimize the refractive index distribution.

[0092] The addition method of Ti is a step-by-step addition, enabling the tungsten oxide layer to smoothly transition to the silicon nitride layer, avoiding composition mutations and reducing the chemical and physical property differences at the interface.

[0093] In summary, in the present invention, a ternary gradient film is formed by adding titanium elements to the gradient film, making the structure of the entire gradient film more stable and enhancing the interfacial bonding force. In addition, the ductility and plasticity of titanium elements can absorb mechanical stress, reducing the risk of film cracking or peeling. Moreover, nano-titanium dioxide particles are added between the titanium targets, which can significantly improve the thermal stability of the intermediate layer and prevent performance degradation at high temperatures. In the present invention, by gradually increasing and gradually decreasing the sputtering of the titanium targets, the tungsten oxide layer, the titanium dioxide layer, and the silicon nitride layer can achieve a smooth transition, thereby effectively enhancing the stability of the material structure, avoiding stress concentration caused by abrupt connection between layers, reducing the risk of problems such as cracks and peeling in the material, and also optimizing the optical and electrical properties of the material. In some optoelectronic devices, it can make the transmission and conversion of light more efficient and the electron migration smoother, thus improving the overall performance of the device. At the same time, the smooth transition is also beneficial to improving the surface flatness of the material, thereby improving the overall quality of the gradient film. In the present invention, the film thickness of the deposition is obtained by monitoring the frequency change of the quartz crystal, thereby determining the film thickness distribution on the rotation radius and obtaining the film thickness distribution on the substrate after single-target sputtering. Finally, based on the film thickness distribution, the revolution speed curve and the revolution speed data of the substrate are obtained, which can effectively improve the uniformity of the gradient film. After establishing the formulas for the relationship between the film thickness data and the revolution speed data and the relationship between the rotation speed and the film thickness, the revolution speed adjustment curve and the revolution rate can be obtained. By using this revolution rate, the uniformity of the gradient film can be effectively improved. At the position where the film thickness is thicker, the revolution speed decreases and the deposition time decreases. At the position where the film thickness is thinner, the revolution speed increases and the deposition time increases. By changing the residence time of the substrate at different positions in the sputtering area in this way, the periodic film thickness at different positions of the substrate can be changed, thereby realizing the control of the film layer thickness.

[0094] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a tungsten oxide and silicon nitride gradient film, characterized in that, The method includes the following steps: S1. Select a substrate and clean the substrate; S2. Evacuate to a base vacuum, introduce high-purity argon and oxygen, start sputtering a tungsten target, and deposit a uniform tungsten oxide layer; S3. Sputter a titanium target at a low frequency, and gradually reduce the sputtering frequency of the tungsten target. When the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the maximum value, and start introducing nitrogen, sputter a silicon target at a low frequency, the sputtering frequency of the silicon target gradually increases, and the sputtering frequency of the titanium target starts to gradually decrease; S4. When the sputtering frequency of the titanium target drops to 0, the sputtering frequency of the silicon target reaches the maximum value, and perform single sputtering of the silicon target; S5. Anneal and polish the gradient film.

2. The preparation method of a tungsten oxide and silicon nitride gradient film according to claim 1, characterized in that, The evacuating to a base vacuum, introducing high-purity argon and oxygen, starting to sputter the tungsten target, and depositing a uniform tungsten oxide layer includes the following steps: S21. Turn on a mechanical pump or a molecular pump and start evacuating the deposition chamber; S22. Introduce high-purity argon and oxygen into the deposition chamber; S23. The substrate rotates, start the magnetron sputtering power supply, apply a voltage to the tungsten target to generate plasma, tungsten atoms are sputtered from the tungsten target, react with oxygen in the deposition chamber to form tungsten oxide, and deposit on the surface of the substrate to form a uniform tungsten oxide thin film.

3. A method for preparing a tungsten oxide and silicon nitride gradient film according to claim 1, characterized in that, The sputtering the titanium target at a low frequency, while gradually reducing the sputtering frequency of the tungsten target. When the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the maximum value, and start introducing nitrogen, sputtering the silicon target at a low frequency, the sputtering frequency of the silicon target gradually increases, and the sputtering frequency of the titanium target starts to gradually decrease includes the following steps: S31. Turn on the revolution of the substrate, while start sputtering the titanium target at a low frequency and gradually reduce the sputtering frequency of the tungsten target. When the sputtering frequency of the tungsten target is reduced to 0, the sputtering frequency of the titanium target reaches the maximum value; S32. Introduce nitrogen and start sputtering the silicon target at a low frequency, the sputtering frequency of the silicon target gradually increases, and the sputtering frequency of the titanium target starts to gradually decrease; S33. When the substrate revolves, monitor the frequency change of the quartz crystal to obtain the deposited film thickness, thereby determine the film thickness distribution on the rotation radius, obtain the film thickness distribution on the substrate after single-target sputtering, and obtain the revolution speed curve and revolution speed data of the substrate according to the film thickness distribution.

4. The preparation method of a tungsten oxide and silicon nitride gradient film according to claim 3, characterized in that, The when the substrate revolves, monitoring the frequency change of the quartz crystal to obtain the deposited film thickness, thereby determine the film thickness distribution on the rotation radius, obtain the film thickness distribution on the substrate after single-target sputtering, and obtain the revolution speed curve and revolution speed data of the substrate according to the film thickness distribution includes the following steps: S331. Establish a formula related to the revolution speed according to the film thickness data, and the specific formula is: T(r) = A∑V(r)τ(ω, r); where r represents the distance from a point on the same plane of the target sputtering area to the center of the plane area; ω represents the revolution speed; τ represents the residence time of a certain point on the substrate in space; V represents the deposition rate distribution in the space above the target, and A is a sputtering constant; S332. When the revolution speed is ω1, the film thickness of any point on the substrate can be expressed as: T1(r) = A∑V(r)τ1(ω, r) = A∑V(r) / ω1; When the revolution speed changes from ω1 to xω1, the residence time of the substrate in space changes to τ / x, and the corresponding film thickness can be expressed as: T2(r) and T1(r) respectively represent the film thicknesses at the revolution rates of xω1 and ω1, τ2(ω, r) and τ1(ω, r) respectively represent the residence times of the substrate at position r at the revolution rates of xω1 and ω1, and x is the multiple of the change in the revolution rate; The angle at which the substrate is swept above the target is divided into n equal parts, and the rotational speed of the j-th equal part is denoted as ω j , then the thickness at a point on the rotation radius of the substrate can be expressed as: Among them, T(r) is, θ is the revolution angle, D(x T , y T ), is the sputtering yield distribution, M is the shielding factor, when the cover plate, baffle or the curved surface edge of the substrate itself of the target causes shielding, M = 0 is taken, and when there is no shielding, M = 1 is taken; cos k α is the angular distribution function of sputtered particles; β is the angle between the incident direction and the normal direction of the substrate when the sputtered material is deposited on the substrate; ρ is the distance from point T on the target to point S on the substrate, dA r is an element on the target; Select a series of discrete points {r i} on the rotation radius, and the corresponding discrete film thickness distribution is {T i}: where r i represents the i-th position on the substrate, determines the film thickness distribution on the rotation radius, given the distribution characteristic parameters of the magnetron sputtering source and the substrate shape, the inversion formula obtains the required revolution speed control curve and revolution rate, and uses the revolution rate to control the revolution rate of the substrate.

5. The preparation method of a tungsten oxide and silicon nitride gradient film according to claim 1, characterized in that, When the sputtering frequency of the titanium target drops to 0, the sputtering frequency of the silicon target reaches the highest value, and the separate sputtering of the silicon target includes the following steps: S41. When the sputtering frequency of the titanium target drops to 0, stop the revolution of the substrate; S42. The substrate continues to rotate and the silicon target is sputtered; S43. When the required film thickness is reached, stop sputtering.

6. A tungsten oxide and silicon nitride-containing gradient film, characterized in that, This gradient film is prepared by the preparation method according to any one of claims 1-5.

7. A tungsten oxide and silicon nitride gradient film according to claim 6, characterized in that, The raw materials for making this gradient film include a substrate, a tungsten target, a silicon target, a titanium target, oxygen, argon, and nitrogen, and the substrate is made of alloy steel; Among them, the production process of the titanium target includes the following steps: Select nano-titanium dioxide particles with a size of 10-100 and a binder, and dissolve the binder in ethanol; mix the nano-titanium dioxide particles with a dispersant and perform ultrasonic dispersion in a solvent, and set the ultrasonic time to 10-30 minutes; slowly add the dissolved binder solution to the dispersed titanium dioxide slurry and stir evenly; remove the solvent from the slurry by drying to form a powder, and finally press the powder into a target.

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