Method and system for electrochemical in-situ characterization of crystal growth interface area change

Abstract

The invention relates to the technical field of crystal growth, and discloses a method and a system for electrochemical in-situ characterization of crystal growth interface area change, and the method comprises the following specific steps: in a crystal growth process by a Czochralski method, measuring impedance between a seed crystal and a crucible containing a melt in real time to obtain an electrochemical impedance spectrum at the growth stage; performing equivalent circuit fitting on the measured electrochemical impedance spectrum to obtain fitting parameters of a corresponding circuit element and calculating equivalent capacitance of a growth interface of the electrochemical impedance spectrum; and calculating the crystal growth interface area through a parallel plate capacitor model based on the equivalent capacitance value. The method solves the problem that the prior art is not suitable for monitoring the crystal growth interface, and has the characteristics of high precision, nondestructive detection, no influence on crystal growth, simple process and controllable cost.

Description

Technical Field

[0001] The present invention relates to the field of crystal growth technology, and more specifically, to a method and system for electrochemical in-situ characterization of crystal growth interface area changes. Background Art

[0002] The Czochralski method has the advantages of producing large crystal size and high quality. It can mass-produce crystals such as yttrium aluminum garnet (YAG), sapphire, and single crystal silicon, providing great support for applications in optics, lasers, semiconductors, and electronic devices. During the Czochralski method crystal growth process, the shape of the growth interface has a crucial influence on the quality of the crystal. However, although the Czochralski method is extremely widely used in crystal growth and a set of mature theories have been formed, the in-situ visualization of the shape and evolution of the growth interface during the Czochralski method crystal growth process has always troubled crystal growth practitioners. Because this is a hidden area, due to the complex melt convection, ultra-high temperature environment, and layers of shielding by the furnace shell insulation material, the real-time monitoring of the growth interface has never been effectively addressed in actual production.

[0003] So far, the commonly used detection method is to take out the growing crystal from the melt to check the interface shape. Obviously, this detection method will completely interrupt the growth process and it is difficult to recover. Secondly, the contact sensors (such as thermocouples) widely used in the current crystal growth process cannot directly contact the growth interface and are not suitable for working in high-temperature melts. At the same time, due to the limitation of resolution, weighing sensors are difficult to show the slight weight changes of the growth interface. In contrast, non-contact sensors, such as infrared probes and image recognition methods (CCD), cannot observe the growth interface and melt changes. Optical imaging and electron beam technology, which are being promoted, can observe the growth interface in real time to a certain extent. However, these methods are limited by crystal transparency, surface reflection and imaging resolution, and their adaptability to different types of crystals is not uniform, making it difficult to achieve the desired effect. Synchrotron radiation, neutron scattering, in-situ electron microscopy and other technologies that are still under research have initially demonstrated the effect of observing dynamic changes of interfaces in melt systems, but such technologies must be operated under specially designed experimental conditions, and most of these methods have radiation risks and require professional equipment and radiation safety measures to avoid harm to operators and the environment. Therefore, the experimental cost is extremely high and it is difficult to apply them in large-scale production. In addition, the use of fluid simulation methods to calculate and simulate the evolution process of the actual crystal growth interface can largely simulate and predict the real-time state of the growth interface, but numerical simulation inevitably idealizes the growth environment. For example, irregular crucible shapes, insulation system defects, and even constantly changing crystals and liquid levels may affect the results of the computational simulation. In summary, for complex, sensitive, hidden and changeable growth interfaces, the existing technologies have their own obvious defects in in-situ observation of the state of the growth interface, which greatly limits their application in actual production. The resulting hidden properties of the growth interface seriously restrict the production of larger size and higher quality crystals. In view of the actual needs of production and the limitations of existing technologies, the crystal industry urgently needs a means to observe and analyze the state of the growth interface in situ.

[0004] In summary, in view of the problem that the existing technology is not suitable for in-situ monitoring of the growth interface, how to invent an in-situ monitoring method of the crystal growth interface area suitable for the Czochralski crystal growth environment is a technical problem that urgently needs to be solved in this technical field. Summary of the invention

[0005] In order to solve the problem that the prior art is not suitable for in-situ monitoring of the growth interface, the present invention provides a method and system for electrochemical in-situ characterization of the change in the area of ​​the crystal growth interface, which has the characteristics of high precision, simple process, non-destructive testing, no hindrance to crystal growth, and controllable cost.

[0006] In order to achieve the above-mentioned purpose of the present invention, the technical scheme adopted is as follows: A method for electrochemical in-situ characterization of crystal growth interface area changes comprises the following specific steps: During the crystal growth process of the Czochralski method, the impedance between the seed crystal and the crucible containing the melt is measured in real time to obtain the electrochemical impedance spectrum at this growth stage; The measured electrochemical impedance spectrum is fitted with an equivalent circuit to obtain the fitting parameters of the corresponding circuit elements and calculate the equivalent capacitance of the growth interface; The crystal growth interface area was calculated using the parallel plate capacitor model based on the equivalent capacitance value.

[0007] Preferably, the impedance spectrum between the seed crystal and the crucible containing the melt is measured in real time, and the specific steps are as follows: Connect the working electrode of the electrochemical workstation to the seed crystal, and also connect its counter electrode to the bottom of the crucible; The crystal growth operation is carried out by the Czochralski method. After the crystal is placed down, the crystal is grown at a constant rotation speed and pulling speed. Each time the crystal grows to a set diameter threshold, the impedance spectrum of the time period is measured by an electrochemical workstation.

[0008] Further, specifically, the working electrode of the electrochemical workstation is connected to the seed crystal through the first wire; the counter electrode is connected to the bottom of the crucible through the second wire; the first wire is led out from the conductive slip ring along the crystal rotating rod and connected to the working electrode of the electrochemical workstation. The second wire is led out from the bottom of the crucible through the growth furnace and connected to the counter electrode of the electrochemical workstation. Furthermore, specifically, the first wire and the second wire are both made of precious metal wire materials, and the growth furnace wall, the first wire and the second wire are all insulated.

[0009] Furthermore, the impedance spectrum of this time period is measured by an electrochemical workstation, specifically: using either constant current EIS or constant voltage EIS, selecting several scales, and performing impedance spectrum measurement within a set time period.

[0010] Furthermore, the electrochemical impedance spectrum is fitted, specifically: the electrochemical impedance spectrum is input into any one of ZSimpWin, CorrView and ZView software for fitting.

[0011] Furthermore, when fitting the electrochemical impedance spectrum, an equivalent circuit is used to fit the equivalent resistance of the growing crystal. , the equivalent resistance of the interface and boundary layer is obtained , the equivalent capacitance impedance CPE of the growth interface is obtained; CPE and in parallel, With CPE and Series connection.

[0012] Furthermore, the fitting parameters of the corresponding equivalent circuit elements are obtained and the equivalent capacitance of the growth interface is calculated. The specific steps are as follows: By fitting the equivalent circuit model, we can get and The value of ; based on the formula , given the EIS test frequency range , obtained through fitting results Dimensional factor and phase index ; Based on the formula , calculate the equivalent capacitance value .

[0013] Furthermore, based on the relevant parameters of the parallel plate capacitor model, the crystal growth interface area S is calculated. The specific steps are: Obtain high temperature melt relative dielectric constant, solute diffusion coefficient, melt kinematic viscosity, and crystal rotation angular velocity; Calculate the thickness of the equivalent parallel plate capacitor at the crystal growth interface :

[0014] in, is the solute diffusion coefficient, is the kinematic viscosity of the melt, is the crystal angular velocity; Based on equivalent capacitance value and the thickness of the growth interface capacitor Calculate the crystal growth interface area :

[0015] in, is the dielectric constant of vacuum, is the relative dielectric constant of the high temperature melt.

[0016] A system for electrochemical in-situ characterization of crystal growth interface area changes, comprising an electrochemical characterization acquisition device and a simulation calculation device; The electrochemical characterization acquisition device is used to measure the impedance between the seed crystal and the crucible containing the melt in real time during the crystal growth process of the Czochralski method to obtain the electrochemical impedance spectrum at the growth stage; The simulation calculation device is used to fit the electrochemical impedance spectrum, obtain the corresponding equivalent circuit element fitting parameters and calculate the equivalent capacitance of its growth interface; and calculate and output the crystal growth interface area based on the equivalent capacitance value.

[0017] The beneficial effects of the present invention are as follows: The present invention discloses a method for electrochemical in-situ characterization of the change in the crystal growth interface area. Different from the traditional thermocouple, weighing sensor, and CCD measurement technology, the present invention creatively adopts the electrochemical impedance spectroscopy method to measure the impedance of the Czochralski growth system, and fits the EIS based on a reasonable equivalent circuit to obtain the equivalent capacitance value of the growth interface, and further calculates the growth interface area based on the equivalent capacitance value, thereby realizing the in-situ characterization of the growth interface by fitting the impedance spectrum of the growth interface. Therefore, the present invention solves the problem that the prior art is not suitable for growth interface monitoring, and has the characteristics of high precision, non-destructive detection, no hindrance to crystal growth, simple process, and controllable cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a schematic flow chart of a method for electrochemical in-situ characterization of crystal growth interface area changes.

[0019] Figure 2 It is a schematic diagram of the structure of the Czochralski crystal growth system in Example 1.

[0020] Figure 3 This is a schematic diagram of the EIS test wiring and lead-out of the Czochralski crystal growth system in Example 1.

[0021] Figure 4 This is a schematic diagram of the growth interface and solute boundary layer parallel plate capacitor in Example 2.

[0022] Figure 5 This is a schematic diagram of the equivalent circuit of the growth system in Example 2.

[0023] Figure 6 These are the original and fitted impedance spectra of EIS-1 in Example 3.

[0024] Figure 7 These are the original and fitted impedance spectra of EIS-2 in Example 3.

[0025] Figure 8 These are the original and fitted impedance spectra of EIS-3 in Example 3.

[0026] Fig. 9 These are the original and fitted impedance spectra of EIS-4 in Example 3.

[0027] Fig.10 This is a graph showing the relationship between the growth interface area and the equivalent capacitance in Example 3. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1 like Figure 1As shown, a method for in situ electrochemical characterization of the change in the crystal growth interface area is used to monitor the Figure 2 The Czochralski crystal growth system shown in the figure grows crystals in a Czochralski furnace. The pulling rod of the system is divided into two parts, one is a precious metal rod connected to the seed crystal, and the other is a crystal rotating rod connected to the motor and the fixed conductive slip ring. The conductive slip ring and the crystal rotating rod are supported by a tripod to achieve a stable and non-eccentric rotation effect. The monitoring method includes the following specific steps: During the crystal growth process of the Czochralski method, the impedance between the seed crystal and the crucible containing the melt is measured in real time to obtain the electrochemical impedance spectrum at this growth stage; The measured electrochemical impedance spectrum is fitted with an equivalent circuit to obtain the fitting parameters of the corresponding circuit elements and calculate the equivalent capacitance of the growth interface; The crystal growth interface area was calculated using the parallel plate capacitor model based on the equivalent capacitance value.

[0030] like Figure 3 As shown, the impedance spectrum between the seed crystal and the crucible containing the melt is measured in real time. The specific steps are: Connect the working electrode of the electrochemical workstation to the seed crystal, and also connect its counter electrode to the bottom of the crucible; The crystal growth operation is carried out by the Czochralski method. After the crystal is placed down, the crystal is grown at a constant rotation speed and pulling speed. Each time the crystal grows to a set diameter threshold, the impedance spectrum of the time period is measured by an electrochemical workstation.

[0031] In this embodiment, the electrochemical workstation measures the impedance spectrum of the growth system in a constant voltage EIS mode, with a scanning frequency range of 100KHz to 0.1Hz, an amplitude of 500mV, a bias voltage of 0V, a logarithmic scale, a total of 60 points, and a measurement time of 3 to 5 minutes. At the same time, a thermometer is used to synchronously record the temperature of the crystal at this time.

[0032] In a specific embodiment, the electrochemical impedance spectrum is fitted, specifically: the electrochemical impedance spectrum is input into CorrView software for fitting.

[0033] In a specific embodiment, when the electrochemical impedance spectrum is fitted, an equivalent circuit is specifically used for fitting to obtain the equivalent resistance of the growing crystal. , the equivalent resistance of the interface and boundary layer is obtained , the equivalent capacitance impedance CPE of the growth interface is obtained; CPE and in parallel, With CPE and Series connection.

[0034] In a specific embodiment, the fitting parameters of the corresponding equivalent circuit element are obtained and the equivalent capacitance of the growth interface is calculated, and the specific steps are as follows: By fitting the equivalent circuit model, we can get and The value of ; based on the formula , given the EIS test frequency range , obtained through fitting results Dimensional factor and phase index ; Based on the formula , calculate the equivalent capacitance value .

[0035] In a specific embodiment, based on the relevant parameters of the parallel plate capacitor model, the crystal growth interface area S is calculated, and the specific steps are: Obtain high temperature melt relative dielectric constant, solute diffusion coefficient, melt kinematic viscosity, and crystal rotation angular velocity; Calculate the thickness of the equivalent parallel plate capacitor at the crystal growth interface :

[0036] in, is the solute diffusion coefficient, is the kinematic viscosity of the melt, is the crystal angular velocity; Based on equivalent capacitance value and the thickness of the growth interface capacitor Calculate the crystal growth interface area :

[0037] in, is the dielectric constant of vacuum, is the relative dielectric constant of the high temperature melt.

[0038] In this embodiment, the relative dielectric constant of the melt is not calculated. The equivalent capacitance value calculated in the first measurement is directly used as a benchmark. Then, the equivalent capacitance values ​​calculated in the subsequent measurements are compared with the benchmark. The evolution law of the growth interface area can be understood, and real-time monitoring of the crystal growth interface area can be achieved.

[0039] Example 2 More specifically, in a specific embodiment, the electrochemical workstation uses a constant current EIS test mode with measurement parameters of: 1000KHZ-0.01HZ, 200mV, bias voltage 1V, linear scale, and measures the impedance spectrum of the time period with a quantitative time.

[0040] In a specific embodiment, the working electrode of the electrochemical workstation is connected to the seed crystal through the first wire; the counter electrode is connected to the bottom of the crucible through the second wire; the first wire is led out from the conductive slip ring along the crystal rotation rod and connected to the working electrode of the electrochemical workstation; the second wire is led out from the bottom of the crucible by the growth furnace and connected to the counter electrode of the electrochemical workstation.

[0041] In this embodiment, a reference electrode is also included. The reference electrode is inserted into the melt. Its wire is the same as the second wire. Both are led out from the bottom of the crucible through the growth furnace and connected to the counter electrode of the electrochemical workstation.

[0042] In this embodiment, all the conductors are made of precious metal wires, and the furnace wall is coated with an insulating layer.

[0043] In a specific embodiment, the first wire and the second wire are both made of precious metal wire materials, and the growth furnace wall, the first wire, and the second wire are all insulated.

[0044] In this embodiment, insulation treatment is performed on the line from the measuring point of the first conductor to the rotating end of the conductive slip ring, the line from the lead-out end of the conductive slip ring of the first conductor to the electrochemical workstation, and the connecting line of the second conductor from the furnace wall to the electrochemical workstation to eliminate interference caused by environmental factors.

[0045] In a specific embodiment, the impedance spectrum of this time period is measured by an electrochemical workstation, specifically: using either constant current EIS or constant voltage EIS, selecting a number of measurement scales, and performing impedance spectrum measurement within a set time period.

[0046] When fitting the electrochemical impedance spectrum, the growth interface and the solute boundary layer are considered to be composed of Figure 4 The parallel plate capacitor structure shown in FIG. Figure 5 The equivalent circuit shown is fitted to obtain the equivalent resistance of the grown crystal. , the equivalent resistance of the interface and boundary layer is obtained , the equivalent capacitance impedance CPE of the growth interface is obtained; CPE and in parallel, With CPE and Series connection.

[0047] In a specific embodiment, the electrochemical impedance spectrum is fitted, specifically: the electrochemical impedance spectrum is input into ZSimpWin software for fitting.

[0048] Furthermore, the fitting parameters of the corresponding equivalent circuit elements are obtained and the equivalent capacitance of the growth interface is calculated. The specific steps are as follows: By fitting the equivalent circuit model, we can get and The value of ; based on the formula , given the EIS test frequency range , obtained through fitting results Dimensional factor and phase index ; Based on the formula , calculate the equivalent capacitance value .

[0049] Furthermore, based on the relevant parameters of the parallel plate capacitor model, the crystal growth interface area S is calculated. The specific steps are: Obtain high temperature melt relative dielectric constant, solute diffusion coefficient, melt kinematic viscosity, and crystal rotation angular velocity; Calculate the thickness of the equivalent parallel plate capacitor at the crystal growth interface :

[0050] in, is the solute diffusion coefficient, is the kinematic viscosity of the melt, is the crystal angular velocity; Based on equivalent capacitance value and the thickness of the growth interface capacitor Calculate the crystal growth interface area :

[0051] in, is the dielectric constant of vacuum, is the relative dielectric constant of the high temperature melt.

[0052] In this embodiment, The method of obtaining the relative dielectric constant is to cut the grown crystal sample and measure the relative dielectric constant; the measurement method is to cut a sample of fixed thickness and crystal orientation, stick platinum electrodes on both sides, connect wires, and then place it in a muffle furnace and heat it to the melting point for measurement, so as to obtain the relative dielectric constant of the grown crystal.

[0053] In this embodiment, the equivalent capacitance value under the corresponding state is obtained by fitting the impedance spectrum under different growth interface states, and then the area of ​​the growth interface can be calculated based on the parallel plate capacitor formula. By comparing the growth interface areas calculated at several different growth stages, the evolution law of the growth interface can be known.

[0054] Electrochemical technology is widely used in energy, environment, materials, medical treatment, sensors and other fields. Among them, electrochemical impedance spectroscopy (EIS) is a common electrochemical characterization method that can be used to study the charge transfer dynamics and interface properties of the target system. It is widely used in semiconductor science, energy conversion and storage technology, chemical sensing and non-invasive diagnosis. The implementation principle of EIS is based on applying a small AC voltage to the measurement system and measuring the current response, and then analyzing the change of the system's impedance with frequency to understand the dynamics, interface behavior and material transfer process of the test system. EIS can analyze the impedance of the system in real time without loss when the target system is in equilibrium or non-steady state.

[0055] The present invention creatively uses the electrochemical impedance spectroscopy (EIS) method to study the capacitance characteristics of the Czochralski crystal growth. The present invention applies a small AC voltage to the growth system and measures its current response, and analyzes the change of the system's impedance with frequency to understand the reaction dynamics, interface behavior, and material transfer process. During the crystal growth process, the growth interface and the solute boundary layer have a similar charging and discharging behavior to that of a capacitor due to the ion segregation caused by pulling and rotation, which is reflected in the Nyquist diagram of the impedance spectrum as an arc composed of imaginary and real data. Therefore, the growth interface state can be analyzed by analyzing the fitting impedance spectrum. EIS is a non-destructive measurement technology. A small AC signal will not cause serious solute concentration polarization and growth interface state changes, nor will it cause physical damage to the growing crystal. It can be measured multiple times during the crystal growth process. At the same time, EIS is very sensitive to changes in the system and can detect small changes in carrier migration or interface characteristics. EIS is also suitable for in-situ monitoring of reaction processes or interface states without interrupting the operation of the test system, and is particularly suitable for long-term test systems such as crystal growth. Based on the excellent performance of the EIS method in situ analysis of the kinetic information and structural information of the reaction process, the present invention relies on the inventor's long-term crystal growth experience, and rationally cross-applications the EIS method with the crystal growth system, realizing the in-situ observation of the area and evolution law of the growth interface during the Czochralski method of growing crystals. In addition, the present invention also provides a new method for calculating the relative dielectric constant of high-temperature melts, providing a new reference for research in related fields. The concavity and convexity of the growth interface can also be effectively reflected by the present invention. When the diameter of the growth interface is constant, the equivalent capacitance values ​​calculated by measuring and calculating at different stages are inconsistent, indicating that the concavity and convexity of the growth interface have changed. In the case of equal diameter growth, the concavity and convexity of the growth interface can be effectively monitored by the present invention, so as to reasonably adjust the shape of the growth interface in time and realize high-quality growth of crystals. Obviously, the present invention can greatly make up for the shortcomings of traditional measurement methods, display the state and evolution law of the growth interface in real time, and the installation and debugging cost of the present invention is low, which is suitable for in-situ observation and analytical application of the growth interface under large-scale production. Thus, the implementation of closed-loop regulation of the growth interface can be greatly promoted, material waste and production costs can be reduced, and crystal quality can be improved. Therefore, the present invention shows important application prospects in the material production of laser crystals, optoelectronic materials, energy devices and other fields. In addition, it also provides researchers with an effective tool to deeply explore the crystal growth mechanism, which can help the development of new materials and new processes, and is expected to significantly promote technological innovation and application in related fields.

[0056] Example 3 This embodiment uses the electrochemical in-situ characterization method of the change in crystal growth interface area of ​​the present invention to conduct experiments. In the experiment, the crystal grown by the Czochralski method is specifically a lithium niobate crystal.

[0057] In the process of growing lithium niobate by Czochralski method, the present invention connects the electrochemical workstation with the Czochralski method crystal growth system, wherein the platinum wire is used as the conductor and a two-electrode system is adopted. The working electrode is connected to the seed crystal, the counter electrode is connected to the bottom of the crucible, and they are connected to the electrochemical workstation through reasonable insulation and lead-out methods to achieve signal input and measurement.

[0058] Then the temperature is raised to grow the crystal. After the raw materials in the crucible with a diameter of 60mm are fully and stably melted, the crystal is placed in the crucible. After the crystal is placed in the crucible, the seed crystal is rotated stably at a speed of 20r / min for 5-10 minutes. Then, the crystal is grown with a shoulder expansion at a pulling speed of 4mm / h, a rotation speed of 20r / min, and a cooling rate of 3℃ / h. In this process, the growth interface size is estimated according to the seed crystal size. When the crystal shoulder is grown to a growth interface diameter of about 20mm, the electrochemical workstation is started, and the constant voltage EIS mode is selected. The electrochemical impedance spectrum when the growth interface diameter is 20mm is measured at 100KHz~0.1Hz, amplitude 500mV, bias 0V, logarithmic scale, recorded as EIS-1, and the measurement time is 3~5min. Within this test time range, the diameter of the crystal grown at a constant pulling speed and rotation speed is almost unchanged, that is, the growth interface area is stable. After that, the shoulder is continued to grow the crystal with expanded diameter. When the growth interface diameter is observed to be about 25mm, 30mm, and 35mm, the impedance spectrum under the interface state is measured, recorded as EIS2, EIS3, and EIS4 respectively. After the measurement is completed, the crystal is pulled off and the sample is retained.

[0059] According to the classical crystal growth boundary layer theory and the structure of the actual crystal growth system, the present invention uses an equivalent circuit to fit the impedance spectrum to obtain the equivalent resistance of the growing crystal. , the equivalent resistance of the interface and boundary layer is obtained , the equivalent capacitance impedance CPE of the growth interface is obtained; CPE and in parallel, With CPE and Series connection.

[0060] like Figure 6 , Figure 7 , Figure 8 , Fig. 9 The impedance spectra EIS1, EIS2, EIS3, and EIS4 were fitted using ZView software; By fitting the equivalent circuit model, we can get and The value of is based on the formula , given the EIS test frequency range ,get Dimensional factor and phase index ; Based on the formula , calculate the equivalent capacitance value ; Calculate the thickness of the equivalent parallel plate capacitor at the crystal growth interface :

[0061] in, is the solute diffusion coefficient, is the kinematic viscosity of the melt, is the crystal angular velocity; Based on equivalent capacitance value and the thickness of the growth interface capacitor Calculate the crystal growth interface area :

[0062] The equivalent capacitance values ​​and growth interface areas corresponding to EIS1, EIS2, EIS3, and EIS4 are obtained.

[0063] The calculated equivalent capacitance values ​​under different growth interface areas are plotted against the estimated growth interface areas. Fig.10The area-capacitance curve shown, and linear fitting, can obviously observe that the equivalent capacitance value is proportional to the growth interface area, which confirms that the growth interface and the solute boundary layer form a structure similar to a parallel plate capacitor, so that the change of the equivalent capacitance value can reflect the size and change of the growth interface area. In this implementation example, the equivalent capacitance value continues to increase, which represents that the growth interface area gradually increases, which is very consistent with the actual results. Subsequently, based on the parallel plate capacitor formula, the diameter of the actual growth interface during the crystal growth process can be calculated. After calculation, the growth interface diameters of EIS1-4 are 21mm, 27mm, 31mm, and 38mm respectively; the diameter of the pull-off retention sample is 39mm, which is highly consistent with the growth interface diameter calculated based on EIS-4, which fully illustrates the accuracy of the in-situ observation of the growth interface area of ​​the present invention. For the lithium niobate crystal grown in this experiment, it can be grown in an atmospheric environment, and it is relatively easy to observe its growth, but the visual error of its growth interface size is still large, and it cannot reflect the concave-convex degree of the growth interface. The method proposed in the present invention can not only be used for crystals grown in an open environment, but also can observe the state and evolution law of the growth interface at each growth stage. For example, the size of the growth interface can be monitored in the shoulder release and diameter expansion stage to meet the needs of size control; in the equal diameter stage, the calculated change in the growth interface area can reflect the degree of concavity of the growth interface to control the shape of the growth interface. More importantly, the present invention can also be used to observe the growth interface of crystals in a fully enclosed black box environment, such as silicon carbide, calcium fluoride, etc., to provide a reliable means of observation for the current blind man's elephant crystal growth mode. In summary, the invention can be applied to a variety of crystal pulling growth processes, and provide great help for the in-situ observation and interpretation of the corresponding crystal growth interface. It will greatly improve the dilemma of inaccurate monitoring and high difficulty of observation of the crystal growth interface, and promote the progress of production.

[0064] Example 4 A system for electrochemical in-situ characterization of crystal growth interface area changes, comprising an electrochemical characterization acquisition device and a simulation calculation device; The electrochemical characterization acquisition device is used to measure the impedance between the seed crystal and the crucible containing the melt in real time during the crystal growth process of the Czochralski method to obtain the electrochemical impedance spectrum at the growth stage; The simulation calculation device is used to fit the electrochemical impedance spectrum, obtain the corresponding equivalent circuit element fitting parameters and calculate the equivalent capacitance of its growth interface; and calculate and output the crystal growth interface area based on the equivalent capacitance value.

[0065] The relative dielectric constant of high temperature melt is obtained by: obtaining a sample of the grown crystal; Cutting samples of the grown crystal into fixed thickness and crystal orientation; Affixing electrodes to both sides of the cut grown crystal sample, and connecting the electrodes on both sides to a relative dielectric constant measuring device; The present invention fully considers the problems of the prior art; traditional measurement technologies, such as thermocouples, weighing sensors, CCD, etc., generally have problems such as poor monitoring accuracy and serious hysteresis, making it difficult to accurately judge the state of the growth interface. Technologies under research, such as X-rays, synchrotron radiation, neutron diffraction, and electron beams, have certain effects on in-situ observation of the shape and dynamic changes of the interface in the Czochralski system, but cannot provide sufficient information, and their harsh experimental conditions, cumbersome operating procedures, high application costs, and high-dose radiation defects limit the practical application of these technologies. Numerical simulation methods based on mathematical modeling and finite element analysis have achieved real-time prediction of the state and evolution of the growth interface to a certain extent, but numerical simulation inevitably idealizes the growth environment. For example, irregular crucible shapes, insulation system defects, and even constantly changing crystals and liquid levels may affect the results of computational simulations.

[0066] In view of the problems of the prior art, the present invention is a method for in-situ characterization of the growth interface area and shape changes during the Czochralski method of growing crystals, which can obtain the real-time growth interface area and evolution law without interfering with the normal growth of the crystal. In the process of Czochralski crystal growth, the state of the growth interface has a decisive influence on the quality of the grown crystal. However, due to the complex melt convection and extremely high temperature environment, the real-time monitoring of the growth interface has never been effectively addressed in actual production.

[0067] In summary, in actual production, real-time monitoring of the growth interface has never been effectively addressed. The resulting non-repeatability of production processes and crystal quality seriously restricts the improvement of production efficiency and the iteration of downstream industries. Obviously, a system that effectively monitors the state of the growth interface in real time can greatly improve the current situation. Therefore, the present invention takes a different approach and proposes to use electrochemical methods for real-time observation of crystal growth based on the viewpoint of interdisciplinary cross-disciplinary. After reasonable equipment transformation and theoretical innovation, the present invention proposes a system that is generally applicable to current crystal growth equipment and does not interfere with normal crystal growth to achieve real-time monitoring of changes in the crystal growth interface area. This in-situ observation and analysis of the growth interface state technology provides real-time feedback on the regulation of the growth interface, which can enable crystal growth practitioners to evaluate the growth interface state in real time, and then adjust the growth parameters in real time according to production needs and crystal growth stages, so that the crystal grows optimally and obtains higher quality crystals. Therefore, the present invention will have a positive impact on understanding the characteristics of the crystal growth interface, guiding crystal production practices, and ensuring a controllable and reproducible crystal growth process, and has great innovative significance and application prospects. It can be widely used in the growth equipment of various single crystal materials such as lithium niobate (LN), yttrium aluminum garnet (YAG), single crystal silicon, etc.

[0068] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for electrochemical in-situ characterization of crystal growth interface area changes, characterized in that: The specific steps include: During the crystal growth process of the Czochralski method, the impedance between the seed crystal and the crucible containing the melt is measured in real time to obtain the electrochemical impedance spectrum at this growth stage; The measured electrochemical impedance spectrum is fitted with an equivalent circuit to obtain the fitting parameters of the corresponding circuit elements and calculate the equivalent capacitance of the growth interface; The crystal growth interface area was calculated using the parallel plate capacitor model based on the equivalent capacitance value.

2. The method for electrochemical in-situ characterization of crystal growth interface area change according to claim 1, characterized in that: Real-time measurement of the impedance spectrum between the seed crystal and the crucible containing the melt. The specific steps are as follows: Connect the working electrode of the electrochemical workstation to the seed crystal, and also connect its counter electrode to the bottom of the crucible; The crystal growth operation is carried out by the Czochralski method. After the crystal is placed down, the crystal is grown at a constant rotation speed and pulling speed. Each time the crystal grows to a set diameter threshold, the impedance spectrum of the time period is measured by an electrochemical workstation.

3. The method for electrochemical in-situ characterization of crystal growth interface area change according to claim 2, characterized in that: Specifically, the working electrode of the electrochemical workstation is connected to the seed crystal through the first wire; the counter electrode is connected to the bottom of the crucible through the second wire; the first wire is led out from the conductive slip ring along the crystal rotation rod and connected to the working electrode of the electrochemical workstation; the second wire is led out from the bottom of the crucible by the growth furnace and connected to the counter electrode of the electrochemical workstation.

4. The method for electrochemical in-situ characterization of crystal growth interface area change according to claim 2, characterized in that: Specifically, the first wire and the second wire are both made of precious metal wire materials, and the growth furnace wall, the first wire and the second wire are all insulated.

5. The method for electrochemical in-situ characterization of crystal growth interface area change according to claim 2, characterized in that: The impedance spectrum of this time period is measured by an electrochemical workstation, specifically: using either constant current EIS or constant voltage EIS, selecting several measurement scales, and performing impedance spectrum measurement within a set time period.

6. The method for electrochemical in-situ characterization of crystal growth interface area change according to claim 1, characterized in that: The electrochemical impedance spectrum is fitted, specifically: the electrochemical impedance spectrum is input into any one of ZSimpWin, CorrView and ZView software for fitting.

7. The method for electrochemical in-situ characterization of crystal growth interface area change according to claim 5, characterized in that: When fitting the electrochemical impedance spectrum, an equivalent circuit is used to fit the equivalent resistance of the growing crystal. , the equivalent resistance of the interface and boundary layer is obtained , the equivalent capacitance impedance CPE of the growth interface is obtained; CPE and in parallel, With CPE and Series connection.

8. The method for electrochemical in-situ characterization of crystal growth interface area change according to claim 6, characterized in that: The fitting parameters of the corresponding equivalent circuit elements are obtained and the equivalent capacitance of the growth interface is calculated. The specific steps are as follows: By fitting the equivalent circuit model, we can get and The value of ; based on the formula , given the EIS test frequency range , obtained through fitting results Dimensional factor and phase index ; Based on the formula , calculate the equivalent capacitance value .

9. The method for electrochemical in-situ characterization of crystal growth interface area change according to claim 6, characterized in that: Based on the relevant parameters of the parallel plate capacitor model, the crystal growth interface area S is calculated. The specific steps are: Obtain high temperature melt relative dielectric constant, solute diffusion coefficient, melt kinematic viscosity, and crystal rotation angular velocity; Calculate the thickness of the equivalent parallel plate capacitor at the crystal growth interface : in, is the solute diffusion coefficient, is the kinematic viscosity of the melt, is the crystal rotation angular velocity; Based on equivalent capacitance value and the thickness of the growth interface capacitor Calculate the crystal growth interface area : in, is the dielectric constant of vacuum, is the relative dielectric constant of the high temperature melt.

10. A system for electrochemical in-situ characterization of crystal growth interface area changes, characterized in that: Including electrochemical characterization acquisition device and simulation calculation device; The electrochemical characterization acquisition device is used to measure the impedance between the seed crystal and the crucible containing the melt in real time during the crystal growth process of the Czochralski method to obtain the electrochemical impedance spectrum at the growth stage; The simulation calculation device is used to fit the electrochemical impedance spectrum, obtain the corresponding equivalent circuit element fitting parameters and calculate the equivalent capacitance of its growth interface; and calculate and output the crystal growth interface area based on the equivalent capacitance value.

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