Optical film thickness real-time brightness value fitting method and system and monitoring system and method

Abstract

The invention provides an optical film thickness real-time brightness value fitting method and system and a monitoring system and method, and is applied to the technical field of optical film thickness monitors and stop judgment in the film plating process. According to the optical film thickness real-time fitting brightness value formula, real-time synchronous fitting is carried out on a transmission curve of film thickness monitoring, a film thickness extreme point and a plating stopping point corresponding to the target thickness are calculated, stopping judgment processing is carried out, effective and accurate stopping judgment processing of the system is achieved, the precision of the monitoring system is larger than 99.5%, and therefore the optical film thickness real-time fitting brightness value formula can be used for real-time fitting of the optical film thickness. The control precision and the stop judgment accuracy are improved on the original basis, and the method can be more widely applied to various coating scenes and shows higher practicability and universality.

Description

Technical Field

[0001] The present application relates to the field of optical film thickness monitoring instruments and the technical field of stop judgment in the film coating process, and in particular to a method and system for real-time fitting brightness value of optical film thickness. Background Art

[0002] With the continuous breakthroughs in science and technology and the accelerated development of industrial transformation, optical thin film devices have become indispensable core components in the fields of military equipment, autonomous driving, fiber optic communications, etc. In particular, high-precision thin film devices such as high-steepness deep-cutoff filters, narrow-band filters and wavelength division multiplexing, these multi-layer film structures have extremely high requirements for the control of optical thickness. Any slight deviation will cause the actual spectrum to deviate from the designed spectrum. The key to film thickness monitoring technology lies in real-time capture and monitoring of multiple variable parameters such as light intensity, transmittance, optical constants, etc. that change with the film thickness. When the set parameters reach the preset standards, the deposition process is terminated. The accuracy of monitoring film thickness data and the judgment stop algorithm are its core technologies. Unlike the crystal control system that controls physical thickness, precise control of film thickness is achieved by directly monitoring parameters that change linearly or nonlinearly with film thickness.

[0003] Currently, domestic research and precision optimization of optical film thickness monitoring algorithms are primarily focused on improving single-wavelength monitoring algorithms based on the photoelectrode value method. For example, by converting the nonlinear relationship between the optical monitoring signal and the optical thickness of the thin film into a linear relationship, a more accurate film thickness extreme point can be calculated, effectively avoiding the interference of nonlinear errors in the determination of extreme points during the thin film deposition process. However, in recent years, algorithm optimization for single-wavelength photoelectrode value monitoring has mainly focused on converting nonlinear operations into linear operations, using mathematical operations to transform the controlled object, or enhancing the monitoring curve fitting extreme points. The control accuracy and universality of the algorithms are relatively limited.

[0004] Based on this, a new technical solution is needed. Summary of the Invention

[0005] In view of this, the present application provides a method and system for real-time fitting of brightness value of optical film thickness, and a monitoring system and method.

[0006] This application provides the following technical solutions:

[0007] According to the present application, a method for real-time fitting of optical film thickness to brightness value is provided, comprising the following steps:

[0008] Model construction steps: Use the photoelectrode value method to construct the mathematical model;

[0009] Real-time fitting step: perform real-time synchronous fitting on the transmission curve of film thickness monitoring, calculate the extreme point of film thickness and the stop plating point corresponding to the target thickness, and perform stop processing.

[0010] Preferably, in the model building step, the characteristic matrix of the absorption film is calculated according to the theory of optical thin film properties; the relationship between the transmittance and reflectivity of the absorption film is obtained according to the characteristic matrix of the absorption film, and the real-time fitting brightness value formula of the optical film thickness is obtained.

[0011] According to the present application, a real-time fitting brightness value system for optical film thickness is also provided, which applies the above-mentioned real-time fitting brightness value method for optical film thickness, including the following modules: a model construction module: a mathematical model is constructed using the photoelectrode value method; a real-time fitting module: a real-time synchronous fitting of the transmission curve of film thickness monitoring is performed, the extreme point of the film thickness and the stop plating point corresponding to the target thickness are calculated, and the stop processing is performed.

[0012] According to a monitoring system also provided by the present application, the above-mentioned method for real-time fitting of brightness value of optical film thickness is applied, including a device adaptation module, a light control function module and a human-computer interaction module; the device adaptation module is used for interactive adaptation between the light control system and the peripheral coating equipment; the light control function module is used for film thickness monitoring signal detection and control within the light control system; the human-computer interaction module is used for data display and parameter adaptation of the light control system.

[0013] According to a monitoring method also provided by the present application, the above-mentioned optical film thickness real-time fitting brightness value method is applied, including: the light control system performs automatic detection, ensures that it is in a normal state, and then sends a self-test success signal; receives the process file parameters of each layer of optical film, completes the conversion and wavelength setting of the photoelectric detector, and transmits instructions to start the coating monitoring process; completes the real-time acquisition of the micro-current amplifier end signal, signal filtering and noise reduction, and fitting the monitoring curve using the optical film thickness real-time fitting brightness value method, and periodically judges the extreme value points and the current film stop plating point in real time; detects the last coating layer, waits for the industrial control system to send an end coating signal, and ends the real-time monitoring of the film thickness; waits for the next coating process.

[0014] Compared with the prior art, the at least one technical solution adopted in this application can achieve the following beneficial effects:

[0015] The dynamic fitting brightness value algorithm for optical film thickness of the present application is the core control algorithm of the optical monitoring system. It can perform real-time synchronous fitting of the transmittance curve of film thickness monitoring, calculate the precise film thickness extreme points and the stop plating points corresponding to any target thickness, and realize effective and accurate stop judgment processing of the system. The accuracy of the monitoring system is greater than 99.5%. Therefore, the real-time fitting brightness value formula for optical film thickness of the present application not only improves the control accuracy and stop judgment accuracy on the original basis, but also can be more widely applied to various coating scenarios, showing stronger practicality and versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. 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 any creative work.

[0017] Figure 1 This is a functional structure diagram of the optical film thickness monitoring system in this application;

[0018] Figure 2 It is the logic flow chart of the software film thickness monitoring system in this application;

[0019] Figure 3 This is a comparison chart of brightness value curves;

[0020] Figure 4 It is the film thickness monitoring curve fitting data diagram in this application;

[0021] Figure 5 It is the residual graph of the film thickness monitoring curve fitting in this application. DETAILED DESCRIPTION

[0022] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0023] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0024] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0025] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0026] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples, however, one skilled in the art will appreciate that the examples can be practiced without these specific details.

[0027] Through in-depth research and improvement exploration on optical thin film thickness monitoring, the applicant found that scholars such as Zhuang Qiuhui, through innovative algorithm design, converted the nonlinear relationship between optical monitoring signals and thin film optical thickness into a linear relationship, thereby being able to deduce more accurate film thickness extreme points, effectively avoiding the interference of nonlinear errors in extreme point determination during the thin film deposition process.

[0028] Scholar Zhao Lei proposed a linear monitoring algorithm. By simultaneously monitoring four groups of monitoring films pre-coated with optical materials and taking the average of the four groups of monitoring signals, the algorithm makes the monitoring transmittance and the actual optical film thickness increase in a linear relationship, thus realizing the linearization of film thickness monitoring for any irregular optical film system.

[0029] Cai Qingyuan and other researchers have developed a new algorithm that converts optical monitoring signals into the phase thickness of a thin film. Using optical admittance plots, they visually display the trigonometric variation of film thickness, accurately monitoring both film reflectivity and deposition thickness. This algorithm converts the relationship between the monitoring signal and optical thickness into a relationship between the monitoring signal and phase thickness, making it more feasible to plot monitoring curves during actual coating processes. However, the algorithm's description of the monitoring signal acquisition, conversion, and processing is still limited and requires further research and verification.

[0030] In addition, researchers such as Chang Min and Hua Bo used heterodyne phase-shift interferometry to accurately measure and calculate the actual reflectivity. This eliminated the deviation between the actual and theoretical reflectivity values when using the photoelectrode value method to monitor film thickness, and reduced the extreme point judgment error caused by the insensitivity of the optical monitoring signal to changes in film thickness near the extreme point. However, this theory mainly corrects the judgment of the extreme point and has not yet addressed the optimization of the judgment accuracy of the stop plating point.

[0031] In recent years, optimization of algorithms for single-wavelength photoelectrode value monitoring has primarily focused on converting nonlinear operations into linear operations, using mathematical operations to transform the controlled object, or enhancing the accuracy of determining extreme value points in monitoring curve fitting. However, the general practicality of these algorithms is relatively limited. However, actual algorithm optimization based on the inherent nonlinear monitoring curve fitting formula is more applicable to more common coating scenarios.

[0032] In recent years, efforts to optimize algorithms for single-wavelength photoelectrode value monitoring have focused on converting nonlinear operations into linear operations, mathematically transforming the controlled object, and improving the accuracy of determining extreme points in the monitoring curve fit. However, the universality and applicability of these algorithms in practical applications are relatively limited.

[0033] Based on this, the technical solutions provided by the various embodiments of the present application are described below in conjunction with the accompanying drawings.

[0034] The embodiment of this specification proposes a method for real-time fitting of optical film thickness to brightness value, such as Figure 2 As shown, the method includes the following steps: Model construction step: A mathematical model is constructed using the photoelectrode value method. Real-time fitting step: The transmission curve of the film thickness monitoring is fitted in real time, the extreme point of the film thickness and the stop point corresponding to the target thickness are calculated, and the stop processing is performed.

[0035] In one embodiment, in the model building step, the characteristic matrix of the absorption film is calculated based on the theory of optical thin film properties; the relationship between the transmittance and reflectivity of the absorption film is obtained based on the characteristic matrix of the absorption film, and the real-time fitting brightness value formula of the optical film thickness is obtained.

[0036] like Figure 3 As shown in the figure, the film thickness monitoring system uses the photoelectrode value method to directly monitor the changing trend of optical film thickness. Although oxygen is introduced during the deposition process of most metal oxides, absorption occurs to a certain extent as the film thickness increases. Traditional formulas do not account for absorption, and absorption during thick film deposition can affect transmittance and brightness, interfering with thickness determination. Therefore, a formula for real-time fitting of optical film thickness to brightness value was derived and integrated into the system as a new algorithm to improve the accuracy of optical film thickness determination. Figure 3 In the figure, Transmittance means transmittance, Non-absorptive means non-absorption, and Absorptive means absorption.

[0037] In one embodiment, in the model building step, according to theoretical calculations of optical thin film properties, the characteristic matrix of the absorption film is:

[0038]

[0039] Where: B is the electric field response under the combined effect of substrate admittance and film phase thickness, and C is the magnetic field effect under the combined effect of film admittance and substrate phase thickness; is the phase thickness of the film layer; η1 is the first effective admittance, η2 is the second effective admittance; i is the imaginary unit.

[0040] In one embodiment, in the model building step, the phase thickness of the film layer Where d1 represents the thickness of the film layer; π represents pi; and the angle of incidence and the angle of refraction are both equal to 0, that is, θ0 = θ1 = 0°. Since the refractive index of the absorbing film is a complex number, the calculation result is as follows:

[0041]

[0042] η j =n j -ik j ;

[0043] Wherein, ch is the hyperbolic cosine function, sh is the hyperbolic sine function; j = 1, 2; n1 is the refractive index of the current film layer; n2 is the refractive index of the substrate and the coated layer; k1 is the extinction coefficient of the current film layer; k2 is the extinction coefficient of the substrate and the coated layer.

[0044] In one embodiment, in the model building step, according to the characteristic matrix of the absorber film, it can be obtained:

[0045]

[0046] The overall formula describes the calculation method of reflectivity, which is obtained by multiplying the reflection coefficient and its complex conjugate. Where R is the reflectivity, r is the reflection coefficient, η0 represents the extinction coefficient of the substrate; the superscript * represents the complex conjugate; the potential transmittance ψ is the ratio of the energy emitted from the film system to the energy entering the film system. The relationship between the transmittance T and the reflectivity of the absorbing film is:

[0047]

[0048] The overall formula describes the calculation method of the transmittance T, which represents the proportion of incident wave energy that transmits through the medium interface. Where ψ is the potential transmittance, which represents the ratio of the energy emitted from the film system to the energy entering the film system;

[0049] Substituting the above formula into the transmittance:

[0050]

[0051] This formula describes how to calculate transmittance T, which is used to analyze the energy transmission of waves (such as electromagnetic waves, light waves, or sound waves) at the interface between two media. n0 represents the refractive index of the substrate.

[0052] in,

[0053]

[0054] In the above formula: d1 is the thickness of the film layer.

[0055] In one embodiment, in the real-time fitting step, a database is established based on the optical constant system of the film and the substrate, data is imported before each layer starts, the physical thickness of the film design is called from the process file, and the composite refractive index is obtained based on the transmittance calculation after the preparation of each layer of the film is completed.

[0056] A database of the optical constants (n, k) of the film and substrate is created, where n represents the refractive index and k represents the extinction coefficient. This data is imported before each layer begins. The film's designed physical thickness, d, is retrieved from the process file, and the composite refractive index, n², is calculated based on the transmittance of each film layer after fabrication. Real-time transmittance, T, and time are directly available in the software, and subsequent data is calculated using the aforementioned formula in real time.

[0057] In one embodiment, in the real-time fitting step, the actual coating data is imported into the nonlinear fitting formula testing software program. After the data is converted into a character string form, the curve fitting control is used to import the optical film thickness real-time fitting brightness value formula to fit the data. After the fitting operation, the mean square error and the monitoring system error are obtained, the optical film thickness monitoring curve is restored, and the extreme value points and stop points are obtained.

[0058] Import the actual coating data into the program, convert the data into a string format, use the curve fitting control, import the optical film thickness real-time fitting brightness value formula to fit the data, the test results are as follows Figure 4 and Figure 5 As shown. After fitting operation, the mean square error is 3.5467×10 -3 The error of the monitoring system is less than 0.01%, which can better meet the requirements of optical film thickness monitoring curve restoration and accuracy of extreme points, stop points, etc.

[0059] The embodiments of this specification also disclose a real-time fitting brightness value system for optical film thickness, which applies the real-time fitting brightness value method for optical film thickness described in any of the above embodiments, including the following modules: a model construction module: a mathematical model is constructed using the photoelectrode value method; a real-time fitting module: a real-time synchronous fitting of the transmission curve of film thickness monitoring is performed, the extreme value point of the film thickness and the stop plating point corresponding to the target thickness are calculated, and a stop judgment process is performed.

[0060] The embodiment of this specification also discloses a monitoring system, such as Figure 1 and Figure 2As shown, the method for real-time fitting of brightness value of optical film thickness described in any of the above embodiments includes a device adaptation module, a light control function module and a human-computer interaction module; the device adaptation module is used for interactive adaptation between the light control system and the peripheral coating equipment; the light control function module is used for film thickness monitoring signal detection and control inside the light control system; the human-computer interaction module is used for light control system data display and parameter adaptation.

[0061] The functional structure of the optical film thickness monitoring system is generally summarized into three parts: film thickness monitoring signal detection and control functions within the optical control system; human-computer interaction functions such as optical control system data display and parameter adaptation; and interaction and adaptation functions between the optical control system and peripheral coating equipment.

[0062] The present specification also discloses a monitoring method, such as Figure 1 and Figure 2 As shown, the method for real-time fitting of brightness value of optical film thickness described in any of the above embodiments includes: the main logic of the optical film thickness monitoring method is: 1. The light control system performs automatic detection to ensure that all equipment and communications are in normal state, and then sends a self-test success signal to the system; 2. Receive the process file parameters of each layer of optical film, complete the conversion and wavelength setting of the photoelectric detector, and transmit instructions to start the coating monitoring process; 3. Complete the real-time acquisition of the micro-current amplifier end signal, signal filtering and noise reduction, fitting of the monitoring curve using the film thickness monitoring algorithm, and stage-by-stage judgment of the extreme point and real-time judgment of the current film stop plating point; 4. Detect that it is the last coating layer, wait for the industrial control system to send an end coating signal, and end the real-time monitoring of the film thickness of the optical film system; 5. Wait for the next coating process.

[0063] This application addresses the current state of research on core optical film thickness control system algorithms for high-precision coating equipment at home and abroad, and conducts research on algorithms for dynamically fitting brightness values for optical film thickness. The research scope includes optical control system software and hardware modules, optical film thickness dynamic fitting brightness value formulas, and the development of optical control software stop judgment formulas. Based on light interference and optical thin film design theory, a mathematical model is constructed using the photoelectrode value method to perform real-time synchronous fitting of the transmission curve for film thickness monitoring, calculate the precise film thickness extreme points and the stop plating points corresponding to any target thickness, and achieve effective and accurate system stop judgment processing, which can solve problems such as precise wavelength positioning and accurate film thickness control in the visible-infrared band.

[0064] In this specification, the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and the relevant parts can be referred to the partial description of the previous embodiments.

[0065] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for real-time fitting brightness value of optical film thickness, characterized in that: The steps include: Model construction steps: Use the photoelectrode value method to construct the mathematical model; Real-time fitting step: perform real-time synchronous fitting on the transmission curve of film thickness monitoring, calculate the extreme point of film thickness and the stop plating point corresponding to the target thickness, and perform stop processing.

2. The method for real-time fitting brightness value of optical film thickness according to claim 1, characterized in that: In the model building step, the characteristic matrix of the absorption film is calculated according to the theory of optical thin film properties; the relationship between the transmittance and reflectivity of the absorption film is obtained according to the characteristic matrix of the absorption film, and the real-time fitting brightness value formula of the optical film thickness is obtained.

3. The method for real-time fitting brightness value of optical film thickness according to claim 2, characterized in that: In the model building step, the characteristic matrix of the absorbing film is: Where: B is the electric field response reflecting the combined effect of substrate admittance and film phase thickness, C is the magnetic field effect reflecting the combined effect of film admittance and substrate phase thickness; δ1 is the phase thickness of the film layer; η1 is the first effective admittance, η2 is the second effective admittance; and i is the imaginary unit.

4. The method for real-time fitting brightness value of optical film thickness according to claim 3, characterized in that: In the model building step, the phase thickness of the film layer Where d1 represents the thickness of the film; π represents the circumference; θ1 represents the refraction angle; and the incident angle θ0 = θ1 = 0°. Since the refractive index of the absorbing film is a complex number, the calculation is: η j =n j -I j ; Wherein, ch is the hyperbolic cosine function, sh is the hyperbolic sine function; j = 1, 2, n1 is the refractive index of the current film layer; n2 is the refractive index of the substrate and the coated layer; k1 is the extinction coefficient of the current film layer; k2 is the extinction coefficient of the substrate and the coated layer.

5. The method for real-time fitting brightness value of optical film thickness according to claim 4, characterized in that: In the model building step, the characteristic matrix of the absorption film is obtained: R＝rr * ； Where R is the reflectivity, r is the reflection coefficient, and the superscript * indicates complex conjugation; The relationship between the transmittance T and reflectivity of the absorbing film is: T=(1-R)ψ; Where ψ is the potential transmittance, which represents the ratio of the energy emitted from the film system to the energy entering the film system.

6. The method for real-time fitting brightness value of optical film thickness according to claim 5, characterized in that: In the real-time fitting step, a database is established based on the optical constant system of the film and substrate. Data is imported before the start of each layer. The designed physical thickness of the film is called from the process file, and the composite refractive index is obtained based on the transmittance calculation after the preparation of each layer of the film is completed.

7. The method for real-time fitting brightness value of optical film thickness according to claim 6, characterized in that: In the real-time fitting step, the actual coating data is imported into the nonlinear fitting formula test software program. After the data is converted into a string form, the curve fitting control is used to import the optical film thickness real-time fitting brightness value formula to fit the data. After the fitting operation, the mean square error and monitoring system error are obtained, the optical film thickness monitoring curve is restored, and the extreme points and stop points are obtained.

8. A real-time fitting brightness value system for optical film thickness, characterized by: The method for real-time fitting brightness value of optical film thickness according to any one of claims 1 to 7 above includes the following modules: a model construction module: a mathematical model is constructed using the photoelectrode value method; a real-time fitting module: a transmission curve for film thickness monitoring is fitted synchronously in real time, the extreme point of film thickness and the stop plating point corresponding to the target thickness are calculated, and a stop judgment process is performed.

9. A monitoring system, characterized in that: The method for real-time fitting of optical film thickness brightness value according to any one of claims 1 to 7 above includes a device adaptation module, a light control function module and a human-computer interaction module; the device adaptation module is used for interactive adaptation between the light control system and the peripheral coating equipment; the light control function module is used for film thickness monitoring signal detection and control within the light control system; and the human-computer interaction module is used for data display and parameter adaptation of the light control system.

10. A monitoring method, characterized in that: The method for real-time fitting brightness value of optical film thickness as described in any one of claims 1 to 7 above includes: the light control system performs automatic detection, ensures that it is in a normal state, and then sends a self-test success signal; receives the process file parameters of each layer of optical film, completes the conversion and wavelength setting of the photoelectric detector, and transmits instructions to start the coating monitoring process; completes the real-time acquisition of the micro-current amplifier end signal, signal filtering and noise reduction, and fitting the monitoring curve using the real-time fitting brightness value method of optical film thickness, and periodically judges the extreme value point and the current film stop plating point in real time; detects the last coating layer, waits for the industrial control system to send a coating end signal, and ends the real-time monitoring of the film thickness; waits for the next coating process.

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