Film thickness control method for vacuum coating and vacuum coating equipment

Abstract

The invention relates to the technical field of vacuum ion plating, and discloses a film thickness control method for vacuum plating and vacuum plating equipment, and the film thickness control method for vacuum plating comprises the following steps: measuring real-time current of a plurality of auxiliary areas around a plating area of a workpiece to be plated; performing time integration and linear regression analysis on the real-time current to obtain an average current value; establishing a film thickness estimation model of the workpiece to be coated according to the average current value; calculating the film thickness in real time based on the film thickness estimation model and feeding back and adjusting film coating parameters to realize closed-loop control of the film thickness; and regularly and actually measuring the thickness of the film layer after film coating, and dynamically correcting the control coefficient of the film thickness estimation model according to actually measured thickness data. By means of the film thickness control method, current information related to the film thickness can be obtained more accurately, monitoring accuracy is improved, film thickness estimation is more accurate, high-precision measurement of the film thickness is achieved, real-time measurement of the film thickness can also be achieved, and repeatability is high.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of vacuum ion plating, and particularly relates to a film thickness control method for vacuum plating and a vacuum plating device. BACKGROUND

[0002] As a key process in the field of modern precision manufacturing, vacuum ion plating technology has been deeply applied to many strategic emerging industries such as optical elements, semiconductor devices, precision cutters, mold manufacturing, high-end decoration and photovoltaic industry. In the field of optics, this technology is used to manufacture core components such as antireflection film, reflective film and optical filter, which directly determines the imaging quality and energy conversion efficiency of devices such as lenses and lasers; in semiconductor manufacturing, vacuum ion plating process is responsible for the preparation of chip passivation layer and metal interconnection layer, and the uniformity of the film layer directly affects the electrical performance and reliability of the device; the surface of industrial cutters and molds can achieve exponential improvement in hardness, wear resistance and corrosion resistance by depositing hard coatings, significantly prolonging the service life of tools; decorative plating film gives products aesthetic value through metal luster or color interference film layer, and is widely used in consumer electronics, watches and building decoration fields; in the photovoltaic industry, the preparation quality of transparent conductive oxide film is directly related to the photoelectric conversion efficiency of solar cells.

[0003] The commonly used film thickness control method is to calculate the film thickness on the basis of the preset plating time, which needs to be based on the premise that the process parameters are extremely stable. However, the actual deposition process is faced with multiple dynamic disturbances: sputtering speed attenuation caused by target material consumption, metal ionization rate oscillation caused by unstable discharge of ion source cathode arc, spatial electric field distribution distortion caused by workpiece clamping position difference, and coupling factors such as vacuum cavity pressure fluctuation and bias power ripple, which together cause real-time drift of ion beam current density. This makes the film thickness calculated by the preset plating time deviate systematically from the actual deposition result, and the film layer thickness dispersion generally exceeds ±10%, which seriously restricts the mass production and consistency of high value-added products.

[0004] In order to break through the limitations of traditional control mode, high-end coating equipment introduces crystal oscillation film thickness meter and ellipsometer and other online monitoring technology, but these schemes still face significant application bottlenecks. Crystal oscillation film thickness meter realizes film thickness measurement through the piezoelectric effect of quartz crystal, however, the measurement accuracy of crystal oscillation film thickness meter is low and the material applicability is limited; ellipsometer has nanometer level measurement accuracy, but the price is expensive, professional spectrum analysis personnel are needed to establish optical model in the operation process, and the size limitation of measurement light spot makes it difficult to deal with complex workpieces with three-dimensional curved surface or microstructure. Especially in the filtered multi-arc ion coating system, the magnetic filter device effectively removes large particle droplets by bending the magnetic field path, significantly improves the film density, but at the same time causes the ion beam current to present the characteristics of uneven spatial distribution, and the asymmetric deposition effect is particularly prominent on large workpieces or special-shaped substrates, so that the traditional point measurement monitoring method cannot accurately reflect the overall film thickness distribution. The existing traditional method responds slowly to the dynamic changing ion flow environment, and it is difficult to realize real-time control with high precision, which ultimately affects the film consistency and process repeatability. SUMMARY

[0005] The purpose of the present application is to overcome the above problems, and provide a film thickness control method for vacuum coating and a vacuum coating equipment, which solves the problems of low film thickness control precision and poor repeatability in existing vacuum coating technology.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions: In a first aspect, the present application provides a film thickness control method for vacuum coating, comprising the following steps: Measuring the real-time current of several auxiliary areas around the film coating area of the workpiece to be coated; Time integration and linear regression analysis are performed on the real-time current to obtain an average current value; Establishing a film thickness estimation model for the workpiece to be coated according to the average current value; Real-time calculation of the film thickness of the workpiece to be coated based on the film thickness estimation model, and feedback adjustment of the coating parameters according to the calculated film thickness of the workpiece to be coated to realize closed-loop control of the film thickness; Periodically measuring the thickness of the film layer after coating, and dynamically correcting the control coefficients of the film thickness estimation model according to the measured thickness data.

[0007] Further improvement of the present application is that in the step of measuring the real-time current of several auxiliary areas around the film coating area of the workpiece to be coated, the several auxiliary areas specifically include symmetric areas located on the right side of the workpiece, the left side of the workpiece, the upper side of the workpiece and the lower side of the workpiece.

[0008] Further improvement of the present application is that the real-time currents of the several auxiliary areas are respectively , , and , the average current is obtained by time integration and linear regression 、 、 and ; The film thickness estimation model is: , In the formula, is the film thickness, 、 、 and is the film thickness control coefficient of each region.

[0009] The film thickness estimation model is simplified to ; In the formula, is the film thickness, is the average current of multiple points, is the overall fitting coefficient.

[0010] The control coefficient in the film thickness estimation model is obtained by multiple linear regression fitting using the least squares method or .

[0011] The specific method for obtaining the control coefficient by multiple linear regression fitting using the least squares method is: Perform multiple film plating tests, and measure the average current and the measured film thickness each time; Time integration and linear regression analysis are performed on the average current data to obtain the average current value; Multiple linear regression fitting is performed using the least squares method; Taking the control coefficient as an example, the calculation formula is:

[0012] In the formula, is the number of tests, ; is the average current of a single experiment; is the average current of the nth experiment; is the measured film thickness of the nth experiment, is the average value of the measured film thickness of the nth experiment; is the average value of the measured film thickness of the nth experiment; is the average value of the measured film thickness of the nth experiment; is the average value of the measured film thickness of the nth experiment; is the average value of the measured film thickness of the nth experiment.

[0013] ​​The further improvement of the present application is that the test times of the multiple linear regression fitting by the least square method are not less than 2 times.

[0014] The further improvement of the present application is that in the step of calculating the film thickness of the workpiece to be plated in real time based on the film thickness estimation model and adjusting the plating parameters according to the calculated film thickness of the workpiece to be plated, the plating parameters include at least one of the plating time, the plasma power and the substrate bias.

[0015] In the second aspect, the present application further provides a vacuum plating equipment, comprising a vacuum ion plating system and a film thickness control system, wherein the film thickness control system is configured to execute the film thickness control method described above, so as to realize the closed-loop feedback control of the film thickness.

[0016] Compared with the prior art, the present application has the following beneficial effects: The present application provides a film thickness control method for vacuum plating. Firstly, the real-time current of several auxiliary areas around the plating area of the workpiece to be plated is measured. By measuring the current of multiple areas in real time, the current information related to the film thickness can be more accurately obtained, and the monitoring accuracy is improved. Secondly, the average current value is obtained by time integration and linear regression analysis of the real-time current, which can effectively reduce the influence of current fluctuation on film thickness estimation and make the data more representative. Then, the film thickness estimation model of the workpiece to be plated is established according to the average current value, so that the film thickness estimation is more accurate. In addition, the film thickness is calculated in real time based on the film thickness estimation model and the plating parameters are adjusted by feedback, so as to realize the closed-loop control of the film thickness, correct the film thickness deviation in time and ensure the stability of the film thickness quality. Finally, the thickness of the film layer after plating is measured regularly and the control coefficient of the corresponding film thickness estimation model is dynamically corrected, which can continuously improve the accuracy of the model and continuously optimize the film thickness control method according to the actual production situation, so as to improve the plating quality and production efficiency. The film thickness control method of the present application not only can realize high-precision measurement of the film thickness, but also can realize real-time measurement of the film thickness with high repeatability. BRIEF DESCRIPTION OF DRAWINGS

[0017] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present application in any way. In addition, the shapes and scale dimensions of the components in the drawings are only illustrative and are used to help understand the present application, and are not specific limitations on the shapes and scale dimensions of the components.

[0018] Figure 1 The flowchart of the film thickness control method for vacuum plating of the present application is shown in the figure; Figure 2 The relationship curve between the side current integration and time of the embodiment of the present application is shown in the figure; Figure 3 The relationship curve between the average current and the film thickness of the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0019] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0021] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0022] In the description of the embodiments of the present application, it should be noted that, if the orientation or position relationship indicated by the terms "upper", "lower", "horizontal", "inner" and the like is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship when the product of the present application is usually placed, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used for differentiation in description, and cannot be understood as indicating or implying relative importance.

[0023] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0024] In the description of the embodiments of the present application, it should also be noted that, unless otherwise explicitly specified and limited, if the terms "set", "mount", "connected", "connected" appear, they should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, can be electrically connected; can be directly connected, can be indirectly connected through an intermediate medium, can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] The present application will be described in further detail below in combination with the accompanying drawings: As Figure 1As shown, the present application provides a film thickness control method for vacuum coating, comprising the following steps: S1, measuring the real-time current of several auxiliary areas around the film-coated area of the workpiece to be coated; Specifically, the several auxiliary areas specifically include symmetric areas located on the right side of the workpiece, the left side of the workpiece, the upper side of the workpiece and the lower side of the workpiece, wherein the real-time current on the right side of the workpiece is represented as , the real-time current on the left side of the workpiece is represented as , the real-time current on the upper side of the workpiece is represented as , and the real-time current on the lower side of the workpiece is represented as .

[0026] S2, time integration and linear regression analysis are performed on the real-time current to obtain an average current value; The average current value is represented as , , and .

[0027] S3, establishing a film thickness estimation model of the workpiece to be coated according to the average current value; The film thickness estimation model is: , In the formula, is the film thickness, , , and is the film thickness control coefficient of each area.

[0028] Preferably, the average current values of all reference areas are summed to obtain a total average current , and the film thickness estimation model can be simplified as ; In the formula, is the film thickness, is the multi-point average current, is the overall fitting coefficient.

[0029] S4, real-time calculation of the film thickness of the workpiece to be coated based on the film thickness estimation model, and feedback adjustment of the coating parameters according to the calculated film thickness of the workpiece to be coated to realize closed-loop control of the film thickness; Specifically, the coating parameters include at least one of the coating time, the plasma power and the substrate bias.

[0030] S5, periodically measuring the thickness of the film layer after coating, and dynamically correcting the control coefficient of the film thickness estimation model according to the measured thickness data.

[0031] Wherein the control coefficient in the film thickness estimation model or The least square method is used for multiple linear regression fitting, and the specific method is as follows: Multiple coating tests are carried out, and the average current and the measured film thickness are measured each time; The average current data is time-integrated and linearly regressed to obtain the average current value; The least square method is used for multiple linear regression fitting; Among them, the control coefficient For example, the calculation formula is:

[0032] In the formula, is the number of tests, ; is the average current of a single experiment; is the average current of the first experiment; is the average current of the first experiment; is the measured film thickness of the first experiment; is the average value of the measured film thickness of the first experiment; is the average value of the measured film thickness of the first experiment.

[0033] Preferably, the number of tests using the least square method for multiple linear regression fitting is not less than 4 times to improve the fitting accuracy and stability.

[0034] The film thickness control method of the vacuum coating of the present application, by testing and real-time monitoring the ion beam current (i.e. corresponding current) change during the working process of the ion coating system, using the time integration method to calculate the total amount of ions reaching the coating area, so as to accurately calculate the real-time film thickness, realize the dynamic monitoring and accurate control of the film thickness of the ion coating system. This method is not only suitable for workpieces with good conductivity, but also can be applied to workpieces with poor conductivity, and has the characteristics of strong adaptability, high expansibility, excellent control precision, etc.

[0035] During the ion coating process, the current signal of the ion beam current during the coating process is collected in real time at the workpiece or sampling point, and the total amount of ions entering the coating area is accurately calculated by combining the time integration method, and further by establishing a linear relationship model between the current and the film thickness, the film thickness is calculated in real time and feedback control is carried out.

[0036] For the workpiece to be coated, multiple current sampling points (workpiece right side, workpiece left side, workpiece upper side and workpiece lower side sampling points) are arranged around the coating area, and the real-time current is measured respectively, and the corresponding average current At this time, the film thickness is related to a linear combination of each average current, that is Or simplify it to: Wherein is the multi-point average current, is the overall fitting coefficient.

[0037] During the coating process, the control system dynamically adjusts the coating time, plasma power or substrate bias and the like according to the film thickness estimation value, and finally realizes real-time accurate control of the film thickness. In order to ensure long-term accuracy, the actual film thickness can be measured regularly in each batch, and the control coefficient Or is corrected.

[0038] This method does not need to introduce additional high-cost equipment, has the advantages of high integration, simple structure, strong adaptability and the like, and is widely applicable to coating processes of different materials and complex workpiece structures.

[0039] The application also provides a vacuum coating equipment, comprising a vacuum ion coating system and a film thickness control system, wherein the film thickness control system is configured to execute the above-mentioned film thickness control method, and realizes closed-loop feedback control of the film thickness.

[0040] The application will be further explained and described below in combination with specific embodiments.

[0041] Embodiment 1: The embodiment provides a film thickness control method for a workpiece to be coated, comprising the following steps: Step S1, in a vacuum ion coating process, real-time current signals of the areas around the workpiece, that is, real-time currents on the right side of the workpiece, real-time currents on the left side of the workpiece, real-time currents on the upper side of the workpiece and real-time currents on the lower side of the workpiece are collected, and the four currents are measured in parallel, so that the total real-time current of the four auxiliary areas around the workpiece coating area is measured, and then a traditional equal-time control method is used, the deposition time is 1000 seconds, and the related parameters of the control coefficient of the application are obtained; Step S2, the collected total real-time current is time-integrated to obtain the total current integral value of the ion beam at each time point within the deposition time , which represents the current integral value in the time interval from 0 to t; Step S3, the current integral value is subjected to linear regression analysis, and the fitting relationship is: Wherein is a fixed constant, which can be calculated by the least square method, and the calculation coefficient The total average current corresponding to the total average current The experimental data is shown in Table 1. Table 1 Experimental data collected by the equal time control method in the embodiment of the application

[0042] Step S4: The film thicknesses measured by four experiments are 9.36 nm, 10.1 nm, 10.5 nm and 11.18 nm, respectively, as shown in Table 1. Figure 2 The corresponding parameters are calculated by the least square method, as shown in Table 1. The dotted line in the figure; through the above results, the film thickness control coefficient is calculated by the least square method. 290.09;

[0043] In the formula, is the number of tests, ; is the average current of a single experiment; is the average current of the nth experiment; is the measured film thickness of the nth experiment, is the average value of the measured film thickness of the four experiments, which is 10.285 nm; is the average value of the four experiments, which is 0.035 mA; The relationship curve between the average current and the film thickness is shown in Table 1, that is, the film thickness ; Step S5: To ensure the long-term stability of the film thickness prediction model, the sample film thickness is measured regularly, and the correction coefficient is fed back to improve the adaptability of the control model. Step S6: The real-time value of the film thickness is compared with the target value (10 nm) to realize closed-loop control. Figure 3 The film thickness control coefficient corresponding to the film thickness control method of the application is obtained through the above steps, and then four film plating experiments are carried out based on the control coefficient. The film thickness experimental data measured by the film thickness control method of the application is shown in Table 2. Table 2 Film thickness experimental data measured by the film thickness control method in the embodiment of the application

[0044]

[0045] ​​​​​From Table 2, the film thickness obtained by using the film thickness control method of the present application is 10.3 nm, 10.5 nm, 10.5 nm and 10.6 nm respectively, and the deviation percentage is -1.67%, 0.24%, 0.24% and 1.19% respectively.

[0046] Step S7, periodically measure the actual film thickness, feedback correction value, to ensure long-term control accuracy.

[0047] Comparative Example 1: In this comparative example, the traditional equal time control method is used for film plating. The workpiece is plated for 1000 seconds of deposition time, and the measured film thickness experimental data is shown in Table 3.

[0048] Table 3 Film thickness experimental data measured by using the traditional equal time control method in the comparative example of the present application

[0049] From Table 3, the film thickness obtained by using the traditional film thickness control method is 10.5 nm, 9.36 nm, 10.1 nm and 11.18 nm respectively, and the deviation percentage is 2.09%, -8.99%, -1.80% and 8.70% respectively.

[0050] According to the experimental data in Table 2 and Table 3, compared with the film thickness control method based on equal length plating time, the film thickness control error of the film thickness control method of the present application can be controlled within ±2%, which significantly improves the film thickness control consistency and greatly improves the film thickness control ability of the ion plating system.

[0051] Many embodiments and many applications other than those provided in the foregoing description are within the scope of the present teachings. Accordingly, the scope of the present teachings should not be determined based on the foregoing description, but instead should be determined based on the following claims as well as equivalents to each of the claims. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. Any aspects of the subject matter disclosed herein that are not recited in the claims are hereby abandoned. For all of the foregoing reasons, the reader is to note that all case law and determinations of validity or unenvalidity made by the United States Patent and Trademark Office, and noted throughout the foregoing description, can he contrary to the claims, and none of which should be read into the claims.

[0052] The foregoing is considered a further description of the present application and should not be construed as limiting the specific embodiments of the present application to what is described herein. For those skilled in the art, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as belonging to the present application as determined by the claims submitted.

Claims

1. A method for controlling the film thickness of a vacuum coating, characterized in that: The following steps are involved: Measuring the real-time current of several auxiliary areas around the coating area of ​​the workpiece to be coated; Performing time integration and linear regression analysis on the real-time current to obtain an average current value; Establishing a film thickness estimation model for the workpiece to be coated based on the average current value; Calculating the film thickness of the workpiece to be coated in real time based on the film thickness estimation model, and adjusting the coating parameters according to the calculated film thickness of the workpiece to be coated, thereby achieving closed-loop control of the film thickness; The thickness of the film layer after coating is measured regularly, and the control coefficient of the film thickness estimation model is dynamically corrected based on the measured thickness data.

2. The method for controlling the film thickness of a vacuum coating according to claim 1, wherein: In the step of measuring the real-time current of several auxiliary areas around the coating area of ​​the workpiece to be coated, the several auxiliary areas specifically include symmetrical areas located on the right side, left side, upper side and lower side of the workpiece.

3. The method for controlling the film thickness of a vacuum coating according to claim 2, wherein: The real-time currents of the several auxiliary areas are respectively 、 、 and , the average current is obtained by time integration and linear regression: 、 、 and ; The film thickness estimation model is: ， Where, is the film thickness, 、 、 and is the film thickness control coefficient of each area.

4. The method for controlling the film thickness of vacuum coating according to claim 3, wherein: The film thickness estimation model is simplified to ; Where, is the film thickness, is the multi-point average current, is the overall fitting coefficient.

5. The method for controlling the film thickness of vacuum coating according to claim 4, wherein: The control coefficient in the film thickness estimation model or All the results were obtained by multivariate linear regression fitting using the least squares method.

6. The method for controlling the film thickness of vacuum coating according to claim 5, characterized in that: The specific method of using the least squares method to perform multiple linear regression fitting to obtain the control coefficient is: Carry out multiple coating tests, measuring the average current and actual film thickness each time; Perform time integration and linear regression analysis on the average current data to obtain the average current value; The least squares method was used for multiple linear regression fitting; Among them, the control coefficient For example, the calculation formula is: Where, is the number of trials, ; is the average current of a single experiment; For the The average current of the experiment; For the The measured film thickness of the test is for The average value of film thickness measured in the test; for Test The average value of .

7. The method for controlling the film thickness of vacuum coating according to claim 6, wherein: The number of experiments for multivariate linear regression fitting using the least squares method is no less than 2.

8. The method for controlling the film thickness of vacuum coating according to claim 1, wherein: In the step of calculating the film thickness of the workpiece to be coated in real time based on the film thickness estimation model, and adjusting the coating parameters according to the calculated film thickness of the workpiece to be coated, the coating parameters include at least one of coating time, plasma power and substrate bias.

9. A vacuum coating device, characterized in that: The invention comprises a vacuum ion plating system and a film thickness control system, wherein the film thickness control system is configured to execute the film thickness control method according to any one of claims 1 to 8 to realize closed-loop feedback control of the film thickness.

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