Deposition method and deposition system of optical thin film

Abstract

The invention provides an optical thin film deposition method and system. The method comprises the steps that the initial position of an evaporation source is determined; determining a movement track of the evaporation source; obtaining a motion trail of the evaporation source and a surface film thickness characteristic equation of the optical element to be deposited; acquiring motion states of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation; performing virtual film coating according to the motion state; when the virtual film coating result is matched with the actual deposition result, optical film deposition can be carried out on the to-be-deposited optical element, the deposition method and system have high universality for the to-be-deposited optical elements with different surface shapes, and no matter the center is provided with a hole, the center is not provided with a hole or other complex optical elements, the deposition efficiency is greatly improved. And uniform deposition can be realized through the method.

Description

Technical Field

[0001] The present application relates to the technical field of thin film preparation, and in particular to a deposition method and deposition system for an optical thin film. Background Art

[0002] Thin film uniformity is one of the important evaluation indicators for the preparation of optical thin films, especially in the current situation where the demand for manufacturing large-aperture optical components is increasing. The uniformity baffles of large-aperture optical components are large in size, and stability is difficult to ensure. In addition, it is difficult to optimize the uniformity of the center position of the lens to be deposited. These have become important issues that optical thin film workers must face. The uniformity of the thickness distribution of optical thin films is particularly important in large-aperture coatings. First, it will cause the optical properties of the entire optical film system to be seriously affected and even destroyed. Secondly, it will affect the surface shape of high-precision optical components, and then affect the performance of the entire optical system. Therefore, when preparing high-performance large-aperture optical thin film components, good film thickness uniformity is a very important requirement.

[0003] Since the development of optical coating technology, the research on film uniformity has always been a hot topic for optical film workers. The methods for adjusting film uniformity can be summarized as the following three: 1. The uniformity of optical thin films is closely related to the relative position of the evaporation source and the optical element to be deposited. Therefore, during the manufacturing process of the coating equipment, the number and position of the evaporation source in the coating equipment and the spatial relative position relationship with the element to be deposited will be optimized to achieve the best film uniformity; 2. The uniformity of different deposition areas is optimized in space by the revolution, rotation or combination of revolution and rotation of the optical element to be deposited. Common substrate rotation methods include plane rotation, planetary rotation, etc.; 3. The uniformity distribution of the evaporation source in the film is optimized by using uniformity correction plates of different shapes. The uniformity of the film can be optimized by designing uniformity baffles of different shapes for different materials.

[0004] Currently, traditional optical film uniformity optimization methods can no longer meet the needs of the ever-increasing aperture and increasingly complex optical component design.

[0005] Therefore, in the face of larger sizes and more complex and diverse designs of optical components in the future, a more efficient and adaptable film uniformity adjustment method is urgently needed to meet the challenges of increasingly complex optical film deposition. Summary of the invention

[0006] In view of this, it is necessary to provide a more universal optical film deposition method and system to address the defect that the traditional optical film uniformity optimization method cannot achieve larger size and more complex and diverse design of optical elements.

[0007] To solve the above problems, this application adopts the following technical solutions:

[0008] One of the purposes of the present application is to provide a method for depositing an optical thin film, comprising the following steps:

[0009] Determine the starting position of the evaporation source;

[0010] Determining the movement trajectory of the evaporation source;

[0011] Obtaining the motion trajectory of the evaporation source and the characteristic equation of the surface film thickness of the optical element to be deposited;

[0012] Obtaining the motion state of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation;

[0013] Performing virtual coating according to the motion state;

[0014] When the virtual coating result is consistent with the actual deposition result, optical thin film deposition can be performed on the optical element to be deposited.

[0015] In some embodiments, the step of determining the starting position of the evaporation source specifically includes the following steps:

[0016] The starting positions of the evaporation sources corresponding to different materials are determined according to the material properties of the designed optical film.

[0017] In some embodiments, the evaporation source is an electron beam evaporation system in physical vapor deposition.

[0018] In some embodiments, the step of determining the motion trajectory of the evaporation source specifically includes the following steps:

[0019] Whether the evaporation source needs to move is determined according to the surface shape of the optical element to be deposited and the deposition function distribution characteristics of the evaporation source. If movement is required, the movement trajectory of the evaporation source is designed.

[0020] In some of the embodiments, the motion trajectory of the evaporation source can be adjusted, and the motion trajectory of the evaporation source includes but is not limited to linear motion, reciprocating motion or other modes of motion; the motion state of the evaporation source can be adjusted, and the motion state includes uniform speed motion or variable speed motion.

[0021] In some embodiments, the step of obtaining the motion trajectory of the evaporation source and the characteristic equation of the surface film thickness of the optical element to be deposited specifically includes the following steps:

[0022] Determine the position change relationship between the evaporation source and the optical element to be deposited when the evaporation source moves along the motion trajectory, and obtain the motion trajectory of the evaporation source and the surface film thickness characteristic equation of the optical element to be deposited, specifically:

[0023] Establishing a geometric relationship between the evaporation source and the optical element to be deposited:

[0024] Establishing a deposition rate function according to the physical characteristics and movement trajectory of the evaporation source;

[0025] Determine the distance between the evaporation source and any point on the optical element to be deposited at each moment according to the deposition rate function;

[0026] The distance between the evaporation source and any point on the optical element to be deposited at each moment is used to obtain a characteristic equation of the surface film thickness.

[0027] In some embodiments, the step of obtaining the motion state of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation specifically includes the following steps:

[0028] Constructing a geometric model of the evaporation source and the optical element to be deposited;

[0029] Determining the relative motion state between the evaporation source and the optical element to be deposited;

[0030] Acquiring the motion state of the evaporation source requires controlling the speed, acceleration, and position change of the evaporation source relative to the optical element to be deposited;

[0031] adjusting the relative position of the evaporation source and the optical element to be deposited according to the position change;

[0032] The relative position and movement state of the evaporation source and the optical element to be deposited are monitored and acquired in real time.

[0033] In some of the embodiments, the step of performing virtual coating according to the motion state specifically includes the following steps: a mathematical model is established to describe the relative position and motion state of the evaporation source and the optical element to be deposited, and the film thickness at different positions is calculated, and the mathematical model includes an evaporation angle model, an evaporation distribution model or a motion trajectory optimization model.

[0034] In some of the embodiments, when the virtual coating result is consistent with the actual deposition result, the step of depositing an optical thin film on the optical element to be deposited can be performed, and the thickness of the optical thin film deposition can be adjusted by the deposition rate of the evaporation source and the moving speed of the evaporation source.

[0035] In some of the embodiments, the surface shape of the optical element to be deposited includes but is not limited to an optical element with a hole in the center or without a hole in the center or an off-axis aspherical surface.

[0036] The second object of the present application is to provide a deposition system for an optical thin film, comprising:

[0037] A position determination module, used to determine the starting position of the evaporation source;

[0038] A trajectory determination module, used to determine the movement trajectory of the evaporation source;

[0039] An equation building module, used to obtain the motion trajectory of the evaporation source and the characteristic equation of the surface film thickness of the optical element to be deposited;

[0040] A motion state determination module, used for obtaining the motion state of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation;

[0041] A virtual coating module, used for performing virtual coating according to the motion state;

[0042] The deposition module is used to deposit an optical thin film on the optical element to be deposited when the virtual coating result is consistent with the actual deposition result.

[0043] This application adopts the above technical solution, and its beneficial effects are as follows:

[0044] The optical thin film deposition method and system provided by the present application determine the starting position of the evaporation source; determine the motion trajectory of the evaporation source; obtain the motion trajectory of the evaporation source and the surface film thickness characteristic equation of the optical element to be deposited; obtain the motion state of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation; perform virtual coating according to the motion state; when the virtual coating result is consistent with the actual deposition result, the optical thin film can be deposited on the optical element to be deposited. The above-mentioned deposition method and system have strong versatility for optical elements to be deposited with different surface shapes, whether there is a hole in the center, no hole in the center or other complex optical elements, uniform deposition can be achieved by this method; in addition, the method can be used without using a uniformity baffle during the deposition process, which greatly reduces the time period caused by the uniformity baffle correction. In addition, the size of the coating equipment required by this method is only slightly larger than the element to be deposited, and there is no need for the size of the coating equipment required in some uniformity optimization situations to be much larger than the element to be deposited. The present invention calculates the deposition situation based on the deposition situation of the evaporation source and the surface shape of the component to be deposited before deposition, and effectively plans the position, relative motion trajectory and state of the evaporation source and the component to be deposited, thereby efficiently realizing the optimization of deposition uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 is a flow chart of the steps of a method for depositing an optical thin film provided by an embodiment of the present invention;

[0047] Figure 2 It is a schematic diagram of the structure of the optical thin film deposition system provided in an embodiment of the present invention.

[0048] Figure 3 It is a schematic diagram of the uniform deposition implementation method used in Example 1 of the present invention.

[0049] Figure 4 It is a schematic diagram of the uniform deposition implementation method used in Example 2 of the present invention. DETAILED DESCRIPTION

[0050] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0051] In the description of the present application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0052] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0053] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0054] See also Figure 1, a step flow chart of a method for depositing an optical thin film is provided for the present application, including the following steps S110 to S160, and the implementation method of each step is described in detail below.

[0055] Step S110: determining the starting position of the evaporation source.

[0056] In this embodiment, the evaporation source is an electron beam evaporation system in physical vapor deposition.

[0057] In this embodiment, the step of determining the starting position of the evaporation source specifically includes the following steps: determining the starting positions of the evaporation sources corresponding to different materials according to the material properties of the designed optical film.

[0058] It should be noted that the starting position of the evaporation source is determined by the melting point, evaporation temperature, evaporation rate, etc. of the material. The melting point, boiling point and evaporation characteristics of each thin film material are different, and the corresponding evaporation source position also needs to be accurately adjusted. The specific solutions include the following:

[0059] For high melting point and high boiling point materials, since high melting point and boiling point materials usually require higher evaporation temperatures, the evaporation source needs to be closer to the substrate to reduce heat loss. For example, for high melting point materials (such as ZrO2, HfO2), these materials have higher evaporation temperatures, so the evaporation source needs to be set close to the substrate. Usually, the initial position of the evaporation source of high melting point materials is selected at a position close to the substrate to ensure heating efficiency and reduce energy loss; for medium melting point materials (such as Al2O3, TiO2), the evaporation rate of these materials is relatively moderate, and the evaporation source can be set at a medium distance from the substrate to balance the heating efficiency and deposition coverage; for low melting point materials (such as MgF2, CaF2), these materials are easy to evaporate, so the evaporation source can be set at a position far away from the substrate to utilize a larger coverage area while preventing the material from evaporating too quickly.

[0060] In addition, the starting positions of the evaporation sources corresponding to materials with different evaporation rates are also different. Materials with faster rates can be kept away from the substrate, while materials with slower rates need to be kept close to the substrate to ensure that sufficient film thickness is deposited within an appropriate time.

[0061] In addition, the starting positions of the evaporation sources corresponding to materials with different thermal conductivities are also different. The better the thermal conductivity of the material, the farther the evaporation source can be moved away from the substrate, because its heating efficiency is higher and the energy transfer efficiency is better.

[0062] In addition, some materials have stronger adhesion at high temperatures, such as silver (Ag), and the evaporation source of these materials should be set at a closer position to prevent splashing and uneven deposition of the material.

[0063] Step S120: determining the movement trajectory of the evaporation source.

[0064] In this embodiment, the step of determining the motion trajectory of the evaporation source specifically includes the following steps: determining whether the evaporation source needs to move according to the surface shape of the optical element to be deposited and the deposition function distribution characteristics of the evaporation source, and if movement is required, designing the motion trajectory of the evaporation source.

[0065] The specific plans include the following:

[0066] Optical component surface shape analysis: First, a detailed analysis is performed based on the specific shape, size, and required film thickness distribution of the optical component to be deposited. If the optical component has a complex non-planar shape (such as a spherical surface, aspherical surface, or other special-shaped curved surface), it usually results in the inability to uniformly deposit the film when the evaporation source is fixed. Therefore, it is necessary to determine whether the evaporation source needs to be moved in combination with the actual component geometry.

[0067] Analysis of the distribution characteristics of the deposition function of the evaporation source: The distribution characteristics of the deposition function of the evaporation source determine the thickness distribution of the film deposited on the substrate when it is at a fixed position. Generally, the deposition function is closely related to the source-substrate distance, evaporation angle, atmosphere pressure, etc. Through experiments or simulation calculations, determine whether the film thickness distribution meets the requirements when the evaporation source position is fixed.

[0068] Determine whether it is necessary to move the evaporation source: Based on the surface shape of the optical component and the deposition characteristics of the evaporation source, if it is found that the film thickness distribution caused by the fixed evaporation source position has a large inhomogeneity and cannot meet the precise requirements of the optical component, it is necessary to adjust the uniformity of the deposition process by moving the evaporation source.

[0069] Evaporation source motion trajectory design:

[0070] Trajectory planning: Design the trajectory of the evaporation source according to the deposition characteristics of the evaporation source and the surface shape of the optical element to be deposited. The design of the trajectory should ensure that the film is evenly distributed on the substrate. Common trajectories include linear, spiral, circular motion, etc. The specific trajectory should be selected according to the shape and size of the element.

[0071] Movement speed and rhythm control: It is necessary not only to determine the movement trajectory of the evaporation source, but also to control its movement speed and rhythm. If the evaporation source moves too fast, the film thickness may be uneven, while if it moves too slowly, the film may be too thick or too thin. By calculating and simulating the effect of the evaporation source movement on the film thickness distribution, the reasonable movement speed and movement rhythm can be determined.

[0072] Adjust the trajectory in combination with real-time feedback: During the actual deposition process, an online thickness monitoring system, such as optical monitoring or crystal control feedback control, can be used to adjust the movement trajectory of the evaporation source in real time according to the actual deposition thickness to ensure the uniformity and accuracy of the film layer.

[0073] It should be noted that the motion trajectory of the evaporation source described in the above technical method can be adjusted, and the evaporation source includes but is not limited to linear motion, reciprocating motion or other motion during the deposition process. The motion state of the evaporation source described in the above technical method can be adjusted, and the evaporation source can perform uniform motion or variable speed motion within a certain speed range during the deposition process, and different motion speeds or motion directions can be set for different positions along the motion trajectory.

[0074] It can be understood that the movement state and movement trajectory of the evaporation source described in the above technical method can be adjusted, which means that its spatial position can be planned before deposition, and the movement state and movement trajectory of the evaporation source during the deposition process can also be planned, and the evaporation source moves according to the set position, movement state and movement trajectory.

[0075] Furthermore, in the above technical method, planning the position, motion state and motion trajectory of the evaporation source refers to calculating and solving the desired motion mode of the evaporation source according to the surface shapes of different elements to be deposited, the properties of materials with different refractive indices and the deposition conditions of the evaporation source.

[0076] Step S130: obtaining the motion trajectory of the evaporation source and the characteristic equation of the surface film thickness of the optical element to be deposited.

[0077] In this embodiment, the step of obtaining the motion trajectory of the evaporation source and the characteristic equation of the surface film thickness of the optical element to be deposited specifically includes the following steps: determining the position change relationship between the evaporation source and the optical element to be deposited when the evaporation source moves along the motion trajectory, and obtaining the motion trajectory of the evaporation source and the characteristic equation of the surface film thickness of the optical element to be deposited.

[0078] Specifically, when determining the position change relationship between the evaporation source and the optical element to be deposited when the evaporation source moves along the motion trajectory and obtaining the characteristic equation of the film thickness, a combination of geometric and physical modeling is usually used. The specific steps are as follows:

[0079] 1. Establish the geometric relationship between the evaporation source and the optical element to be deposited

[0080] Define geometric parameters: First, define the geometric parameters of the evaporation source (position, size, angle, etc.) and the geometric characteristics of the optical element to be deposited (surface shape, size, position, etc.). Important parameters include the distance between the evaporation source and the substrate, the evaporation angle, the opening angle of the evaporation source, the size and curvature of the substrate, etc.

[0081] Motion trajectory description: According to the designed evaporation source movement trajectory (straight line, spiral, circle, etc.), define the motion equation of the evaporation source relative to the optical element. Let the evaporation source position be R(t), where t represents time, which describes the position change of the evaporation source on the motion trajectory.

[0082] 2. Establishing a deposition rate function based on the physical properties and motion trajectory of the evaporation source;

[0083] Specifically, according to the physical characteristics and motion trajectory of the evaporation source, the deposition rate function is established where θ is the evaporation angle, is the azimuth angle. This function can be obtained through experimental measurement or theoretical calculation. Generally, the deposition rate varies with the evaporation angle and has radial symmetry.

[0084] 3. Determine the distance between the evaporation source and any point on the substrate at each moment according to the deposition rate function;

[0085] Specifically, the distance D(x, y, t) between the evaporation source and any point on the substrate at each moment is determined, where (x, y) is the coordinate on the substrate surface, and the distance change will directly affect the thickness distribution of the film.

[0086] 4. Obtain a characteristic equation for the surface film thickness based on the distance between the evaporation source and any point on the substrate at each moment.

[0087] Specifically, an integral accumulation model is established: the film thickness is the result of the accumulation of the evaporation source during the entire movement process. Assuming the film thickness is h(x,y), the film thickness can be obtained by integration:

[0088]

[0089] where t0 and t f are the start and end times of evaporation, respectively. This formula describes the accumulation of film thickness on the substrate over time during the movement of the evaporation source.

[0090] Furthermore, considering symmetry and trajectory optimization: for optical elements with strong symmetry (such as spherical or planar elements), the equations can be simplified. For example, when the evaporation source moves along a circular trajectory, the film thickness is only related to the radial distance. In this case, the characteristic equation of film thickness can be simplified to:

[0091]

[0092] where r is the radial distance from the point on the base to the center.

[0093] Numerical simulation optimization: For optical components with complex surface shapes, finite element analysis or numerical methods can be used to solve and optimize the above equations, and further adjust the motion trajectory of the evaporation source to make the film thickness distribution more uniform.

[0094] It can be understood that in practice, the motion trajectory (speed, acceleration, etc.) of the evaporation source can be adjusted according to the calculation results so as to obtain a uniform film thickness distribution on the entire substrate surface, for example, including:

[0095] Feedback control: Introduce online measurement systems (such as light control, crystal control, etc.) to monitor film thickness in real time, and adjust the motion trajectory of the evaporation source according to real-time feedback to ensure the uniformity and accuracy of film thickness.

[0096] Through these steps, the relationship between the evaporation source motion and the film thickness distribution can be accurately established, and high-quality and uniform film deposition can be achieved through optimized trajectory design.

[0097] Step S140: obtaining the motion states of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation.

[0098] During the thin film deposition process, by adjusting the relative motion state between the evaporation source and the substrate, the film thickness distribution can be accurately controlled to achieve a uniform deposition effect. To obtain the motion state at different relative positions, the following technologies and methods are usually required:

[0099] 1. Constructing a geometric model of the evaporation source and the optical element to be deposited;

[0100] First, it is necessary to construct a geometric model of the evaporation source and the optical element to be deposited. Assuming that the optical element to be deposited is placed on a certain plane or curved surface, the movement of the evaporation source relative to the optical element to be deposited can be described by a trajectory such as a straight line, a circle, or a spiral.

[0101] The main purpose of establishing a geometric model is to determine the shape of the optical element to be deposited. The optical element to be deposited can be a plane, spherical, aspherical, etc. Its shape will affect the calculation of the film thickness distribution.

[0102] Define the location and trajectory of the evaporation source: The evaporation source can move along different trajectories, such as straight lines, curves on a plane, or complex trajectories in three-dimensional space. The trajectory can be described by geometric parameters such as angle, distance, speed, etc.

[0103] 2. Determine the relative motion state between the evaporation source and the optical element to be deposited;

[0104] Specifically, the relative motion state between the evaporation source and the optical element to be deposited can be described by the following parameters:

[0105] The relative position of the evaporation source and the substrate: R(t) represents the position of the evaporation source relative to the substrate at time t, where R(t) = (x(t), y(t), z(t)) is the three-dimensional coordinate of the evaporation source.

[0106] Motion trajectory equation: describes how the evaporation source moves along the preset trajectory. For motion on a two-dimensional plane, the equation R(t) = f(T) can be used to describe the change of position over time; in three-dimensional space, the changes of x(t), y(t), and z(t) must be considered simultaneously.

[0107] 3. Obtaining the motion state of the evaporation source requires controlling the speed, acceleration, and position change of the evaporation source relative to the optical element to be deposited;

[0108] To obtain the motion state of the evaporation source, it is necessary to control the velocity, acceleration and position change of the evaporation source relative to the substrate. The key control parameters include:

[0109] Speed ​​v(t): The speed of the evaporation source relative to the substrate, which is usually achieved through a motor and a control system in actual control systems. The control of speed directly affects the deposition rate.

[0110] Acceleration a(t): The acceleration change of the evaporation source can be used to adjust the speed stability and ensure the uniformity of the film thickness. On a larger diameter substrate, maintaining a constant acceleration can make the deposition process more stable.

[0111] Trajectory shape and path planning: By optimizing the motion trajectory, the film thickness can be adjusted in a specific area. For example, adjusting the motion trajectory of the evaporation source to a spiral shape can evenly cover the substrate over a large area.

[0112] 4. Adjusting the relative position of the evaporation source and the optical element to be deposited according to the position change;

[0113] In order to ensure uniform film deposition, the relative position of the evaporation source and the substrate needs to be adjusted according to the film thickness requirements. This can be achieved by the following methods:

[0114] Distance d(t) between the evaporation source and the substrate: The film thickness is inversely proportional to the distance from the evaporation source to the substrate. By calculating the distance between the evaporation source and the substrate in real time, the motion trajectory is adjusted to ensure that the required thickness is obtained at different positions.

[0115] Deposition rate The deposition rate is calculated based on the evaporation angle θ and the azimuth angle φ. The angle change of the evaporation source directly affects the deposition rate at each position, and the deposition thickness can be changed by adjusting the posture of the evaporation source.

[0116] 5. Monitor and obtain the relative position and motion state of the evaporation source and the optical element to be deposited in real time.

[0117] During the deposition process, sensors and measurement systems are used to monitor the relative position and motion state of the evaporation source and substrate in real time. Combined with feedback control technology, precise adjustment of the motion trajectory can be ensured. The main methods include:

[0118] Laser interferometer: used to measure the relative distance between the evaporation source and the substrate, and dynamically adjust the movement of the evaporation source based on the measurement results.

[0119] Crystal control: Measure the real-time changes in deposition rate and adjust the movement speed and trajectory of the evaporation source through feedback.

[0120] Light control: Monitor the film thickness in real time during the deposition process, and adjust the relative position of the evaporation source and the substrate through feedback to ensure the uniformity of the film thickness.

[0121] Furthermore, to obtain the motion state of the evaporation source at different relative positions, it is also necessary to use a motion trajectory optimization algorithm. Commonly used methods include:

[0122] Dynamic trajectory planning algorithm: Design the trajectory of the evaporation source according to the preset film thickness distribution. By dynamically adjusting the movement speed and path of the evaporation source, precise control of the film thickness can be achieved.

[0123] Edge coupling compensation algorithm: For large-diameter substrates, the deposition in the edge area is often prone to uneven thickness. The algorithm adjusts the motion trajectory of the evaporation source to make the deposition uniformity of the edge and center areas consistent.

[0124] It is understood that when obtaining the motion state of different relative positions, the motion of the evaporation source can also be simulated by simulation software. For example, finite element analysis (FEM) software can simulate the film thickness distribution of the evaporation source under different trajectories, helping to optimize the motion state and reduce errors in the experiment.

[0125] Through the above-mentioned technical means and methods, the relative movement state of the evaporation source and the substrate can be accurately controlled to ensure ideal thickness uniformity and excellent optical properties during the thin film deposition process.

[0126] Step S150: performing virtual coating according to the motion state.

[0127] In this embodiment, in the step of performing virtual coating according to the motion state, the following steps are specifically included: by establishing a mathematical model to describe the relative position and motion state of the evaporation source and the substrate, the film thickness at different positions is calculated, and the mathematical model includes an evaporation angle model, an evaporation distribution model or a motion trajectory optimization model.

[0128] It can be understood that virtual coating is a technology that predicts the film thickness distribution and optical properties by simulating the film deposition process by computer. The following is a detailed description of how to perform virtual coating based on the motion state:

[0129] Virtual coating uses mathematical models, physical simulation and computer technology to simulate the thin film deposition process in real environment. During the thin film deposition process, the relative motion state of the evaporation source and the substrate will directly affect the thickness distribution of the thin film. Through virtual coating technology, the deposition process under different motion states can be simulated in advance on the computer, so as to optimize the process parameters and achieve uniform thin film deposition. Specifically, it includes the following steps:

[0130] 1. Input parameter setting: In order to perform virtual coating, some key input parameters need to be set first. These parameters directly determine the accuracy of virtual coating, including:

[0131] Evaporation source parameters: including the type of evaporation source, evaporation rate, evaporation angle and power, etc. These parameters affect the movement direction and speed of the evaporated material and determine its deposition method on the substrate.

[0132] Substrate shape and size: The shape (such as plane, curved surface, spherical surface, etc.) and size of the substrate will affect the distribution of the material on the substrate, especially the surface deposition distribution of large-aperture optical components.

[0133] Relative motion trajectory of the evaporation source and the optical element to be deposited: Set the movement trajectory, speed and angle of the evaporation source relative to the substrate. Through different trajectory designs (such as spiral, reciprocating, etc.), the film thickness distribution can be optimized.

[0134] 2. Establish a mathematical model of the relative motion between the evaporation source and the optical element to be deposited

[0135] By establishing a mathematical model to describe the relative motion state between the evaporation source and the substrate, the film thickness at different positions can be calculated. Commonly used models include:

[0136] Evaporation angle model: Calculate the amount of evaporated material deposited at different points on the substrate surface based on the relative distance and angle between the evaporation source and the substrate. The deposition rate R can be expressed as:

[0137] R(θ)=R0COS(θ)

[0138] Where R0 is the deposition rate at the center position and θ is the angle between the evaporation source and the substrate surface point.

[0139] Evaporation distribution model: According to the geometric shape and material distribution of the evaporation source, the process of evaporation material diffusion from the source to the substrate is simulated. A two-way flow model can be used to describe the path of material diffusion from the evaporation source to the outside, and it can be corrected in combination with actual physical parameters (such as temperature and pressure).

[0140] Motion trajectory optimization model: Based on the dynamic trajectory planning algorithm, the influence of the motion path and speed of the evaporation source at different positions on the deposition thickness is calculated. By simulating different trajectories, the best motion state is selected to optimize the uniformity of film thickness.

[0141] 3. Calculation of film thickness distribution during virtual coating process based on mathematical model

[0142] During the evaporation process, the film thickness at each point on the substrate will be different. Based on the motion trajectory, evaporation angle, and the relative position of the evaporation source and the substrate, the film thickness distribution can be calculated by the following steps:

[0143] a) Calculate the evaporation rate at each position: According to the relative motion state and distance between the evaporation source and the substrate, the evaporation rate at each position is calculated using the evaporation angle model. The higher the evaporation rate, the thicker the film.

[0144] b) Cumulative thickness distribution: Based on the motion trajectory and deposition time, the thickness of each point on the substrate is accumulated. Through simulation software (such as MATLAB, COMSOL, etc.), the deposition thickness at each moment can be accumulated to obtain the thickness distribution of the entire deposition process.

[0145] c) Thickness distribution correction: By comparing the deposition effects under different motion trajectories, the motion path and rate of the evaporation source can be adjusted in real time in the virtual coating to optimize the uniformity of the final film.

[0146] It should be noted that the simulation software that can also be used in the virtual coating process includes:

[0147] COMSOL Multiphysics: Simulate complex physical fields (such as temperature fields, motion fields of evaporation sources and substrates) to predict thickness distribution during deposition.

[0148] MATLAB: Used to calculate complex deposition trajectories and optimize the geometric relationship between the evaporation source and the substrate.

[0149] Essential Macleod: Compute the optical properties of multilayer thin film systems, especially changes in reflectivity, transmittance, and absorptivity.

[0150] Through virtual coating technology, the thin film deposition process can be simulated without actual experiments, providing an important reference for the optimization of the actual coating process, saving experimental costs and improving the controllability of the process.

[0151] Step S160: When the virtual coating result is consistent with the actual deposition result, optical thin film deposition can be performed on the optical element to be deposited.

[0152] It can be understood that the thickness of the deposited optical thin film can be adjusted by the deposition rate of the evaporation source and the moving speed of the evaporation source.

[0153] It should be noted that the surface shapes of the different elements to be deposited described in the above method include but are not limited to those with a hole in the center, those without a hole in the center, off-axis aspheric optical elements, etc. The elements to be deposited described in the above technical method can rotate or be fixed, which means that during the deposition process, the elements to be deposited can rotate or be stationary according to specific deposition requirements.

[0154] The above-mentioned deposition method has strong versatility for optical elements to be deposited with different surface shapes. Whether it is a center hole, a center hole-free or other complex optical elements, uniform deposition can be achieved by this method; in addition, this method can be used without the use of a uniformity baffle during the deposition process, which greatly reduces the time period caused by the correction of the uniformity baffle. In addition, the size of the coating equipment required by this method only needs to be slightly larger than the element to be deposited, and there is no need for the size of the coating equipment required in some uniformity optimization situations to be much larger than the element to be deposited. Based on the deposition situation of the evaporation source and the surface shape of the element to be deposited, the present invention calculates the deposition situation before deposition, and effectively plans the position, relative motion trajectory and state of the evaporation source and the element to be deposited, thereby efficiently realizing the optimization of deposition uniformity.

[0155] See also Figure 2 , which is a schematic diagram of the structure of the optical thin film deposition system provided in this embodiment, comprising:

[0156] A position determination module 110, used to determine the starting position of the evaporation source;

[0157] A trajectory determination module 120, used to determine the movement trajectory of the evaporation source;

[0158] An equation building module 130 is used to obtain a motion trajectory of the evaporation source and a characteristic equation of a surface film thickness of an optical element to be deposited;

[0159] A motion state determination module 140, configured to obtain the motion state of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation;

[0160] A virtual coating module 150, used for performing virtual coating according to the motion state;

[0161] The deposition module 160 is used to deposit an optical thin film on the optical element to be deposited when the virtual coating result is consistent with the actual deposition result.

[0162] The detailed working method of the optical thin film deposition system provided in the embodiment of the present application can be found in the above-mentioned deposition method, which will not be repeated here.

[0163] The above-mentioned deposition system has strong versatility for optical elements to be deposited with different surface shapes. Whether it is a center hole, a center hole-free or other complex optical elements, uniform deposition can be achieved through this method; in addition, this method can be used without the use of a uniformity baffle during the deposition process, which greatly reduces the time period caused by the correction of the uniformity baffle. In addition, the size of the coating equipment required by this method only needs to be slightly larger than the element to be deposited, and there is no need for the size of the coating equipment required in some uniformity optimization situations to be much larger than the element to be deposited. Based on the deposition situation of the evaporation source and the surface shape of the element to be deposited, the present invention calculates the deposition situation before deposition, and effectively plans the position, relative motion trajectory and state of the evaporation source and the element to be deposited, thereby efficiently realizing the optimization of deposition uniformity.

[0164] The above technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0165] Example 1

[0166] Schematic diagram of deposition method Figure 3 As shown, the optical element A to be deposited is a large-aperture plane mirror without a hole in the center. The specific steps are as follows:

[0167] 1) According to the surface characteristics of the optical element to be deposited, a large-aperture plane mirror without a hole in the center, it is determined to use a fixed electron beam evaporation source B, analyze the film-forming characteristics of high and low refractive index materials through experiments and calculations, adjust the height of the element to be deposited, and fix the positions of the two material evaporation sources B and B';

[0168] 2) Since the optical element to be deposited is rotationally symmetric, the element to be deposited is made to rotate C during the deposition process, and the evaporation source can make a linear motion D along the center direction of the optical element to be deposited, and finally stay at a good evaporation position corresponding to the high and low refractive index materials;

[0169] 3) Obtaining thickness uniformity deposition characteristics of different materials when the evaporation source B is at different positions on the linear trajectory D;

[0170] 4) According to the above thickness uniformity distribution characteristics, combined with the linear trajectory D of the evaporation source and the rotation condition C of the element to be deposited, the deposition position of the evaporation source B is optimized, and different deposition positions are selected for different materials;

[0171] 5) Using the calculated position information of the evaporation source to perform virtual coating, obtain virtual coating results, and experimentally verify the results of the virtual coating;

[0172] 6) After confirming that the virtual coating result is consistent with the actual deposition result, the sample A to be deposited can be deposited, and finally a uniform thin film is obtained on its surface.

[0173] Example 2

[0174] Schematic diagram of deposition method Figure 4 As shown, the optical element to be deposited is a large-diameter, large-off-axis aspheric surface with no hole in the center. The specific steps are as follows:

[0175] 1) According to the surface characteristics of the optical element to be deposited, a large-aperture, large-off-axis aspheric surface F with no hole in the center, it is determined to use a mobile electron beam evaporation system E as the evaporation source, and the deposition function distribution characteristics of the evaporation source E are analyzed through experiments and calculations;

[0176] 2) Since the optical element to be deposited is not rotationally symmetrical and has a large off-axis amount, the deposition method prevents the element to be deposited from rotating during the deposition process, and the evaporation source can reciprocate along the surface of the optical element to be deposited G and cover the entire surface of the optical element to be deposited;

[0177] 3) obtaining the distribution characteristics of the deposition of the evaporation source E on the element to be deposited F when the evaporation source E is at different positions of the motion trajectory G;

[0178] 4) According to the above deposition distribution characteristics and combined with the motion trajectory G of the evaporation source, the motion state of the deposition process of the evaporation source E is solved;

[0179] 5) Using the solved motion state of the evaporation source to perform virtual coating, obtain the virtual coating result, and experimentally verify the result of the virtual coating;

[0180] After confirming that the virtual coating result is consistent with the actual deposition result, deposition can be performed on the sample F to be deposited, and finally a uniform thin film is obtained on its surface.

[0181] It can be understood that the technical features of the above-described embodiments can be arbitrarily combined. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0182] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims

1. A method for depositing an optical thin film, characterized in that: The steps include: Determine the starting position of the evaporation source; Determining the movement trajectory of the evaporation source; Obtaining the motion trajectory of the evaporation source and the characteristic equation of the surface film thickness of the optical element to be deposited; Obtaining the motion state of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation; Performing virtual coating according to the motion state; When the virtual coating result is consistent with the actual deposition result, optical thin film deposition can be performed on the optical element to be deposited.

2. The method for depositing an optical thin film according to claim 1, wherein: The step of determining the starting position of the evaporation source specifically includes the following steps: The starting positions of the evaporation sources corresponding to different materials are determined according to the material properties of the designed optical film.

3. The method for depositing an optical thin film according to claim 1 or 2, characterized in that: The evaporation source is an electron beam evaporation system in physical vapor deposition.

4. The method for depositing an optical thin film according to claim 1, wherein: The step of determining the motion trajectory of the evaporation source specifically includes the following steps: Whether the evaporation source needs to move is determined according to the surface shape of the optical element to be deposited and the deposition function distribution characteristics of the evaporation source. If movement is required, the movement trajectory of the evaporation source is designed.

5. The method for depositing an optical thin film according to claim 4, wherein: The motion trajectory of the evaporation source can be adjusted, and the motion trajectory of the evaporation source includes but is not limited to linear motion, reciprocating motion or other modes of motion; the motion state of the evaporation source can be adjusted, and the motion state includes uniform speed motion or variable speed motion.

6. The method for depositing an optical thin film according to claim 1, wherein: The step of obtaining the motion trajectory of the evaporation source and the characteristic equation of the surface film thickness of the optical element to be deposited specifically includes the following steps: Determine the position change relationship between the evaporation source and the optical element to be deposited when the evaporation source moves along the motion trajectory, and obtain the motion trajectory of the evaporation source and the surface film thickness characteristic equation of the optical element to be deposited, specifically: Establishing a geometric relationship between the evaporation source and the optical element to be deposited: Establishing a deposition rate function according to the physical characteristics and motion trajectory of the evaporation source; determining the distance between the evaporation source and any point on the optical element to be deposited at each moment according to the deposition rate function; A characteristic equation of the surface film thickness is obtained according to the distance between the evaporation source and any point on the optical element to be deposited at each moment.

7. The method for depositing an optical thin film according to claim 1, wherein: The step of obtaining the motion state of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation specifically includes the following steps: Constructing a geometric model of the evaporation source and the optical element to be deposited; Determining the relative motion state between the evaporation source and the optical element to be deposited; Acquiring the motion state of the evaporation source requires controlling the speed, acceleration, and position change of the evaporation source relative to the optical element to be deposited; adjusting the relative position of the evaporation source and the optical element to be deposited according to the position change; The relative position and movement state of the evaporation source and the optical element to be deposited are monitored and acquired in real time.

8. The method for depositing an optical thin film according to claim 1, wherein: The step of performing virtual coating according to the motion state specifically includes the following steps: The film thickness at different positions is calculated by establishing a mathematical model to describe the relative position and motion state of the evaporation source and the optical element to be deposited. The mathematical model includes an evaporation angle model, an evaporation distribution model or a motion trajectory optimization model.

9. The method for depositing an optical thin film according to claim 1, wherein: When the virtual coating result is consistent with the actual deposition result, the step of optical thin film deposition can be performed on the optical element to be deposited, and the thickness of the optical thin film deposition can be adjusted by the deposition rate of the evaporation source and the moving speed of the evaporation source.

10. The method for depositing an optical thin film according to claim 1, wherein: The surface shape of the optical element to be deposited includes but is not limited to an optical element with a hole in the center or without a hole in the center or an off-axis aspherical surface.

11. An optical thin film deposition system, characterized in that: include: A position determination module, used to determine the starting position of the evaporation source; A trajectory determination module, used to determine the movement trajectory of the evaporation source; An equation building module, used to obtain the motion trajectory of the evaporation source and the characteristic equation of the surface film thickness of the optical element to be deposited; A motion state determination module, used for obtaining the motion state of the evaporation source and the optical element to be deposited at different relative positions according to the surface film thickness characteristic equation; A virtual coating module, used for performing virtual coating according to the motion state; The deposition module is used to deposit an optical thin film on the optical element to be deposited when the virtual coating result is consistent with the actual deposition result.

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