Method and system for in-situ characterization of crystal state in crystal growth process by Czochralski method
By using an electrochemical workstation to measure the electrochemical impedance spectrum of the crystal during the lifting process, and calculating the crystal length through equivalent circuit fitting, the problem of difficult to achieve high-precision, lossless and real-time measurement in high-temperature environments in the prior art is solved, and high-precision crystal state monitoring is achieved.
Patent Information
- Application Number
- CN202411882577.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-19
- Publication Date
- 2025-05-06
AI Technical Summary
During the process of lifting the method, it is difficult for the prior art to achieve high-precision, lossless, real-time measurement of crystal resistance and length. It is affected by factors such as high-temperature environment, mechanical vibration and external interference, resulting in a decrease in measurement error and accuracy.
An electrochemical workstation was used to measure the impedance between seed crystals and crucibles in real time, and the crystal temperature was recorded through a thermometer to obtain the electrochemical impedance spectrum. Through equivalent circuit fitting, the equivalent resistance and length of the crystal are calculated.
Real-time monitoring of high-precision, lossless and non-hindering crystal growth during the process of growing crystals with lifting method is realized, ensuring crystal quality, optimizing growth process and improving production efficiency.
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Figure CN119934947A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of crystal growth, and more specifically, to a method and system for in-situ characterization of a crystal state during a crystal growth process using a Czochralski method. Background Art
[0002] For decades, the endless emergence of crystal materials has supported the development of the optical and electronic fields. Whenever new crystal materials are developed or new crystal growth technology breaks through, it can always bring huge benefits to the optical, laser, semiconductor, electronic devices, radiation detection and other industries. Among the crystal growth methods, the most widely used is the Czochralski (CZ) method, which can be used to pull out a variety of crystals, such as single crystal silicon, lithium niobate, scheelite, and most oxide crystals such as ruby, sapphire, artificial yttrium aluminum garnet (YAG), artificial gadolinium gallium garnet (GGG), chrysoberyl, spinel, etc.; as well as most scintillating crystals such as bismuth germanate (BGO), cerium fluoride (CeF3), barium fluoride (BaF3), thallium-doped cesium iodide (CsI), lead tungstate (PWO), etc., providing irreplaceable technical support for industrial production and application.
[0003] Although the Czochralski method is widely used in crystal growth and has formed a set of mature theories, the real-time and reliable measurement of the crystal state during the Czochralski method, especially the real-time and reliable measurement of resistance and length, has always troubled crystal growth practitioners. Because during the Czochralski method growth process, the crystal and the melt are in a high temperature environment (usually up to 1200°C or above), excessively high temperatures will cause many measuring devices to fail or degrade in performance, and conventional measuring devices and sensors cannot work properly in this environment. At the same time, the crystal is constantly pulled up and rotated during the growth process, and its shape and position change dynamically over time. It is difficult for the measuring device to have sufficient dynamic response capabilities, and the failure to adjust the measurement position and parameters in time will greatly affect the measurement accuracy. In addition, during the crystal growth process, slight temperature fluctuations, mechanical vibrations, and external interference will lead to measurement errors, and it is difficult to maintain high-precision in-situ measurements.
[0004] In the process of crystal growth by the Czochralski method, traditional methods for measuring crystal resistance and length mainly include optical measurement technology, mechanical measurement technology, resistance measurement technology and applied electric field technology. These methods can monitor the crystal growth process to a certain extent, but there are many limitations. Optical measurement technologies such as laser interferometry, laser reflection method and optical microscopy are widely used in the growth process of semiconductor single crystal silicon, generally using laser or camera technology to monitor the growth length and surface state of the crystal. However, this type of measurement method is affected by factors such as crystal surface reflectivity, transparency and optical interference, and the measurement accuracy is not high; and the optical system is usually complex and expensive, and the universality is poor. Mechanical measurement technology such as mechanical displacement sensor, mechanical probe measurement, etc., the measurement equipment is simple and direct, and the length of the growing crystal can be obtained to a certain extent, but this type of method cannot avoid the measurement error caused by the drop in the liquid level, and the mechanical probe is easy to damage the crystal surface, affecting the crystal quality; mechanical parts are also prone to failure in high temperature environments, requiring regular maintenance and calibration, which increases the complexity of operation. Resistance measurement techniques such as the four-probe method and resistivity meter cannot measure resistance in real time during crystal growth and can only be analyzed after growth is completed. In addition, the arrangement and poor contact of the measuring electrodes can easily affect the measurement results. In high temperature and high vacuum environments, the stability and reliability of resistance measurement equipment are difficult to guarantee. The applied electric field technology usually applies a voltage or current to the Czochralski growth system, measures its response value, and calculates the resistance of the crystal. However, in order to achieve the desired effect, the applied electric field value is usually large, which will greatly interfere with the normal growth of the crystal, causing crystal cracking and uneven distribution of components. The continuous movement and change of the crystal during the growth process also requires complex tracking and dynamic adjustment mechanisms, which increases the complexity of the system. In addition, the resistance calculated by this method includes the internal resistance of the melt and crucible, and there is a large error with the actual crystal internal resistance. In summary, there are many difficulties in measuring the resistance and length of the crystal in situ during the Czochralski crystal growth process. Although the existing technology can provide a certain reference, it faces many technical challenges and limitations in practical applications. The field of crystal growth urgently needs further technological breakthroughs to overcome these problems.
[0005] In summary, in view of the problem that the existing measurement technology is not suitable for the crystal growth environment of the Czochralski method, how to invent a method and system for in-situ characterization of the crystal state during the crystal growth process of the Czochralski method is a technical problem that urgently needs to be solved in this technical field. Summary of the invention
[0006] In order to solve the problem that the existing measurement technology is not suitable for the crystal growth environment of the Czochralski method, the present invention provides a method and system for in-situ characterization of the crystal state during the crystal growth process of the Czochralski method, which has the characteristics of high precision, non-destructive measurement, no hindrance to crystal growth, and strong real-time performance.
[0007] In order to achieve the above-mentioned purpose of the present invention, the technical scheme adopted is as follows: A method for in-situ characterization of a crystal state during a Czochralski method crystal growth process comprises the following specific steps: During the Czochralski crystal growth process, the impedance between the seed crystal and the crucible containing the melt is measured in real time, and the crystal temperature is recorded using a thermometer to obtain the electrochemical impedance spectrum at this growth stage and its corresponding crystal temperature; Several electrochemical impedance spectra were fitted with equivalent circuits to obtain the equivalent resistance of the crystal corresponding to each growth stage; Based on the equivalent resistance and corresponding crystal temperature fitted at each growth stage, the corresponding crystal length is calculated.
[0008] Preferably, during the crystal growth process of the Czochralski method, an electrochemical workstation is used to measure the impedance between the seed crystal and the crucible containing the melt in real time, and a thermometer is used to record the crystal temperature. 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; install the thermocouple of the thermometer on the seed crystal; The Czochralski crystal growth operation is carried out. After the crystal is placed down, the crystal is grown at a constant rotation speed and pulling speed, and the growth diameter of the crystal is monitored in real time. Each time the crystal grows to the set diameter threshold, the impedance spectrum of the growth stage is measured by the electrochemical workstation, and the corresponding crystal temperature is recorded.
[0009] Furthermore, the impedance between the seed crystal and the crucible containing the melt is measured in real time, and the crystal temperature is recorded using a thermometer, specifically: the counter electrode of the electrochemical workstation and the bottom of the crucible are connected via the first wire; the working electrode and the seed crystal are connected via the second wire; the thermometer and the thermocouple are connected via the third wire; the first wire is led out from the bottom of the crucible by the growth furnace where the Czochralski crystal is grown, and connected to the counter electrode of the electrochemical workstation; the second and third wires are led out from the rotating device of the crystal rotating rod along the crystal rotating rod, and are respectively connected to the working electrode and the thermometer of the electrochemical workstation.
[0010] Furthermore, specifically, the connection line of the first wire from the growth furnace to the electrochemical workstation, the connection line of the second wire from the conductive slip ring to the electrochemical workstation, and the connection line of the third wire from the conductive slip ring to the thermometer are all insulated.
[0011] Furthermore, an electrochemical workstation is used to measure the impedance between the seed crystal and the crucible containing the melt in real time. Specifically, either constant current EIS or constant voltage EIS is used, and several measurement scales are selected during the crystal growth stage. The impedance spectrum is measured within a set time period, and the crystal is grown with equal diameter according to the set parameters. The impedance spectrum is measured with the same parameters every time the crystal is pulled for a period of time.
[0012] Furthermore, the electrochemical impedance spectrum is fitted with an equivalent circuit, specifically: the electrochemical impedance spectrum is input into any software such as ZView, ZSimpWin, or CorrView for fitting, thereby extracting the resistance R of the growing crystal. C .
[0013] Furthermore, if the Czochralski crystal growth process does not adopt the flat shoulder form to grow the crystal, the electrochemical impedance spectrum when the shoulder is completed is also measured and obtained, and the electrochemical impedance spectrum is fitted with an equivalent circuit to obtain the crystal resistance when the shoulder is completed.
[0014] Furthermore, based on the equivalent resistance and corresponding crystal temperature obtained by fitting at each growth stage, the corresponding crystal length is calculated, specifically: If the crystal growth process of the Czochralski method does not adopt the flat shoulder form to grow the crystal, then the resistance value of the crystal at each growth stage obtained by fitting is subtracted from the resistance value of the crystal at the stage of shoulder completion to obtain the resistance value of the equal diameter part of the crystal at each growth stage; According to the corresponding temperature of the crystal at each growth stage, the corresponding resistivity formula is found and its resistivity is calculated; based on the crystal diameter corresponding to each growth stage, the cross-sectional area of the crystal is obtained; according to s / , calculate the length of the crystal at each growth stage; is the resistance of the equal diameter part of the crystal, is the crystal resistivity, is the crystal length, s is the cross-sectional area of the crystal.
[0015] Furthermore, based on the equivalent resistance and corresponding crystal temperature obtained by fitting at each growth stage, the corresponding crystal length is calculated, specifically: If the Czochralski method is used to grow crystals in a flat shoulder form, then the corresponding resistivity formula is found and the resistivity is calculated based on the corresponding temperature of the crystal at each growth stage; the cross-sectional area of the crystal is obtained based on the corresponding crystal diameter at each growth stage; according to s / , calculate the length of the crystal at each growth stage; is the crystal resistance, is the crystal resistivity, is the crystal length, s is the cross-sectional area of the crystal.
[0016] A system for in-situ characterization of the crystal state during the crystal growth process by the Czochralski method, comprising an electrochemical characterization collection 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 Czochralski crystal growth process, and use a thermometer to record the crystal temperature to obtain the electrochemical impedance spectrum at the growth stage and the corresponding crystal temperature; The simulation calculation device is used to perform equivalent circuit fitting on several electrochemical impedance spectra to obtain the equivalent resistance of the crystal corresponding to each growth stage; based on the equivalent resistance fitted at each growth stage and the corresponding crystal temperature, the corresponding crystal length is calculated and output.
[0017] The beneficial effects of the present invention are as follows: The present invention discloses a method for in-situ characterization of a crystal state during a Czochralski method crystal growth process. The invention creatively adopts electrochemical impedance spectroscopy to in-situ measure the resistance of the crystal during the Czochralski method crystal growth process and further obtain its corresponding length, thereby realizing real-time, non-destructive and high-precision crystal state monitoring. The real-time measurement of the crystal resistance and length is of great significance for ensuring the quality of the crystal, optimizing the growth process and improving the production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a schematic flow chart of a method for in-situ characterization of crystal state during crystal growth by the Czochralski method of the present invention.
[0019] Figure 2 It is a schematic diagram of the structure of the Czochralski crystal growth system used in Example 1.
[0020] Figure 3 Schematic diagram of the EIS test wiring method of the Czochralski crystal growth system used in Example 1.
[0021] Figure 4 This is a schematic diagram of the crystal during the Czochralski growth process in Example 3.
[0022] Figure 5 This is a schematic diagram of an equivalent circuit for impedance spectrum fitting of the Czochralski crystal growth system in Example 3.
[0023] Figure 6 It is a schematic diagram of the impedance spectrum curve measured and fitted during the seed crystal in Example 3.
[0024] Figure 7 It is a schematic diagram of the impedance spectrum curve measured and fitted when the shoulder release is completed in Example 3.
[0025] Figure 8 It is a schematic diagram of the impedance spectrum curve measured and fitted when the medium diameter growth is performed for 2 hours in Example 3.
[0026] Fig. 9 It is a schematic diagram of the impedance spectrum curve measured and fitted during 4 hours of medium diameter growth in Example 3. DETAILED DESCRIPTION
[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.
[0028] Example 1 like Figure 1 As shown, a method for in-situ characterization of the crystal state during the Czochralski method of growing crystals is suitable for Figure 2 The Czochralski crystal growth system shown in the figure, in which the pulling rod is divided into two sections, one section is a precious metal rod connected to the seed crystal, and the other section 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 fixed by a tripod, and the specific steps are as follows: During the Czochralski crystal growth process, the impedance between the seed crystal and the crucible containing the melt is measured in real time, and the crystal temperature is recorded using a thermometer to obtain the electrochemical impedance spectrum at this growth stage and its corresponding crystal temperature; Several electrochemical impedance spectra were fitted with equivalent circuits to obtain the equivalent resistance of the crystal corresponding to each growth stage; Based on the equivalent resistance and corresponding crystal temperature fitted at each growth stage, the corresponding crystal length is calculated.
[0029] In a specific embodiment, Figure 3 As shown, during the Czochralski crystal growth process, an electrochemical workstation is used to measure the impedance between the seed crystal and the crucible containing the melt in real time, and a thermometer is used to record the crystal temperature. 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; install the thermocouple of the thermometer on the seed crystal; The Czochralski crystal growth operation is carried out. After the crystal is placed down, the crystal is grown at a constant rotation speed and pulling speed, and the growth diameter of the crystal is monitored in real time. Each time the crystal grows to the set diameter threshold, the impedance spectrum of the growth stage is measured by the electrochemical workstation, and the corresponding crystal temperature is recorded.
[0030] In a specific embodiment, the impedance between the seed crystal and the crucible containing the melt is measured in real time, and a thermometer is used to record the crystal temperature, specifically: the counter electrode of the electrochemical workstation and the bottom of the crucible are connected through the first wire; the working electrode and the seed crystal are connected through the second wire; the thermometer and the thermocouple are connected through the third wire; the first wire is led out from the bottom of the crucible by the growth furnace where the Czochralski crystal is grown, and connected to the counter electrode of the electrochemical workstation; the second wire and the third wire are led out from the rotating device of the crystal turning rod along the crystal turning rod, and are respectively connected to the working electrode and the thermometer of the electrochemical workstation.
[0031] In this embodiment, the first conductive wire, the second conductive wire, and the third conductive wire are all made of precious metal wires.
[0032] In a specific embodiment, the connection line of the first wire from the growth furnace to the electrochemical workstation, the connection line of the second wire from the conductive slip ring to the electrochemical workstation, and the connection line of the third wire from the conductive slip ring to the thermometer are all insulated.
[0033] In a specific embodiment, an electrochemical workstation is used to measure the impedance between the seed crystal and the crucible containing the melt in real time. Specifically, either constant current EIS or constant voltage EIS is used, and several measurement scales are selected during the crystal growth stage. The impedance spectrum is measured within a set time period, and the crystal is grown with equal diameter according to the set parameters, and the impedance spectrum is measured with the same parameters every time it is pulled for a period of time.
[0034] In this embodiment, the impedance spectrum of the Czochralski system was measured by constant voltage EIS using an electrochemical workstation, with a scanning frequency range of 100 KHz to 0.1 Hz, an amplitude of 500 mV, a logarithmic scale, a total of 60 points, and a measurement time of 2 to 3 minutes.
[0035] In a specific embodiment, the electrochemical impedance spectrum is fitted with an equivalent circuit, specifically: the electrochemical impedance spectrum is input into any software such as ZView, ZSimpWin, or CorrView for fitting, thereby extracting the resistance R of the growing crystal. C .
[0036] In a specific embodiment, if the Czochralski crystal growth process does not adopt the flat shoulder form to grow the crystal, the electrochemical impedance spectrum when the shoulder is released is also measured and obtained, and the electrochemical impedance spectrum is fitted with an equivalent circuit to obtain the crystal resistance when the shoulder is released.
[0037] In a specific embodiment, based on the equivalent resistance and the corresponding crystal temperature obtained by fitting at each growth stage, the corresponding crystal length is calculated, specifically: The crystal growth process of the Czochralski method does not adopt the flat shoulder form to grow the crystal. The resistance value of the crystal at the shoulder completion stage is subtracted from the crystal resistance value obtained by fitting at each growth stage to obtain the resistance value of the equal diameter part of the crystal at each growth stage. According to the corresponding temperature of the crystal at each growth stage, the corresponding resistivity formula is found and its resistivity is calculated; based on the crystal diameter corresponding to each growth stage, the cross-sectional area of the crystal is obtained; according to s / , calculate the length of the crystal at each growth stage; is the resistance of the equal diameter part of the crystal, is the crystal resistivity, is the crystal length, s is the cross-sectional area of the crystal.
[0038] In this embodiment, the crystal cross-sectional area can be obtained by any method such as estimation based on the growth diameter, real-time estimation, real-time monitoring using a charge coupled device camera CCD, or estimation using a real-time weight sensor.
[0039] Example 2 In this embodiment, during the Czochralski crystal growth process, an electrochemical workstation is used to measure in real time the impedance between the seed crystal and the crucible containing the melt, and a three-electrode system including a reference electrode is used, and the reference electrode is connected by inserting it into the melt.
[0040] In this embodiment, an electrochemical workstation is used to measure the impedance between the seed crystal and the crucible containing the melt in real time. Specifically, a constant current EIS test method is used to measure the impedance spectrum of the Czochralski system, with a scanning frequency range of 100 KHz to 0.1 Hz, an amplitude of 200 mV, and a linear scale.
[0041] In this embodiment, the corresponding crystal length is calculated based on the equivalent resistance and corresponding crystal temperature obtained by fitting at each growth stage. Specifically, if the Czochralski method adopts a flat shoulder form to grow the crystal, then according to the equivalent resistance and corresponding temperature of the crystal at each growth stage, the corresponding resistivity formula is found and the resistivity is calculated; the crystal cross-sectional area is obtained based on the crystal diameter corresponding to each growth stage; according to s / , calculate the length of the crystal at each growth stage; is the crystal resistance, is the crystal resistivity, is the crystal length, s is the cross-sectional area of the crystal.
[0042] Example 3 More specifically, in this embodiment, a method for in-situ characterization of the crystal state during the CZO process of growing a crystal is also used to in-situ measure the crystal resistance and length during the CZO process of growing a lithium niobate crystal.
[0043] In this embodiment, the electrochemical workstation is connected to the Czochralski system, wherein a platinum wire is used as a conductor, the positive electrode (WE) is connected to the seed crystal, and the negative electrode (CE) is connected to the bottom of the crucible; a thermocouple is also connected to the seed crystal to record the temperature of the crystal throughout the growth process.
[0044] In the present embodiment, after the raw material is fully stably melted, the lower crystal operation is performed, and the seed crystal is stably rotated at a speed of 15r / min for 10 minutes after the lower crystal. Immediately after starting the electrochemical workstation, the constant voltage EIS mode is selected, and the electrochemical impedance spectrum under the seed crystal state is measured in a manner of 100KHz~0.1Hz, amplitude 500mV, bias 0V, and logarithmic scale, denoted as EIS-1, and the measurement time is 2~3min, and the temperature of the crystal is T1. Subsequently, the crystal is grown at a pulling speed of 2mm / h and a speed of 15r / min, and the cooling rate is 2°C / h. When the crystal shoulder is grown to a diameter of about 40mm, equal diameter growth is started, and the electrochemical workstation is started at this time, and the constant voltage EIS mode is selected. The electrochemical impedance spectrum when the shoulder is completed is measured with the same parameters, denoted as EIS-2, and the crystal temperature is denoted as T2. After entering the equal diameter stage, the crystal was grown at a constant temperature at a pulling speed of 2 mm / h and a rotation speed of 15 r / min. After 2 hours of growth, the impedance spectrum at this time was measured by an electrochemical workstation with the same parameters, recorded as EIS-3, and the crystal temperature at this time was recorded as T3. After that, the crystal was grown at the same diameter for another 2 hours, and then the impedance spectrum at this time was measured by an electrochemical workstation, recorded as EIS-4, and the crystal temperature at this time was recorded as T4.
[0045] In this experiment, the electrochemical impedance spectroscopy measurement method with small amplitude and short period will not interfere with the normal growth of the crystal, and the crystal quality will not be significantly affected.
[0046] In this embodiment, after all data are measured, the crystal is pulled off to end the crystal growth process. The crystal of the entire growth process is as follows: Figure 4 As shown, combined with the actual Czochralski crystal growth system structure and the measured EIS-1, the equivalent circuit obtained by fitting is as follows Figure 5 As shown, R C Represents the crystal resistance, R S represents the charge transfer resistance of the melt, and CPE represents the equivalent capacitance of the melt double electric layer. Figure 6 As shown, the seed resistance R is obtained by fitting the equivalent circuit based on the EIS-1 data. C1 =70.77Ω, which is highly consistent with the seed crystal resistance of 72.6Ω measured at the same temperature in the muffle furnace, which fully demonstrates the reliability of in-situ measurement of crystal resistance using the EIS method. Subsequently, EIS-2, EIS-3, and EIS-4 were fitted with the equivalent circuit, and the fitting results are shown in the figure. Figure 7 , Figure 8 , Fig. 9 As shown, the crystal resistance R C2 =260.2Ω, crystal resistance R after 2h of equal diameter growth C3 =302.3Ω, crystal resistance R after 4h of equal diameter growth C4=372.5Ω, then compare the measured resistance value with the resistance of a crystal of the same size and good quality at this temperature. If there is a large deviation, it means that the quality of the grown crystal has major defects.
[0047] Subtract the resistance of the crystal when the shoulder is completed from the resistance of the crystal measured after 2h and 4h of equal diameter growth to get the resistance of the equal diameter part of the crystal, that is, the resistance of the 2h equal diameter crystal is 42.1Ω, and the resistance of the 4h equal diameter crystal is 112.3Ω. Based on the law of resistance s / , and the previously measured resistivity distribution formula of lithium niobate crystal in the temperature range of 1293K-1513K: , T is the thermodynamic temperature, and the lengths of the 2h isodiametrically grown crystal and the 4h isodiametrically grown crystal are calculated respectively.
[0048] The lengths of the 2h isodiametric growth crystal and the 4h isodiametric growth crystal are calculated respectively. Specifically, according to the corresponding temperatures T3 (1395K) and T4 (1382K) during the measurements of EIS-3 and EIS-4, it can be calculated that the resistivity of the 2h isodiametric growth crystal and the 4h isodiametric growth crystal are 49.78Ω / m and 66.62Ω / m, respectively. At the same time, the diameter of the crystal is 40mm. Therefore, the lengths of the 2h isodiametric growth crystal and the 4h isodiametric growth crystal are 4.25mm and 8.47mm, respectively. Obviously, this is highly consistent with the pulling speed of 2mm / h. The reason why the pulling height is slightly less than the crystal length is mainly due to the drop in the liquid level. This is also the benefit of the present invention, and the crystal growth part promoted by the drop in the liquid level can be extracted in situ.
[0049] Finally, the crystal length measured in situ by the EIS method is compared with the length of the actual grown crystal. It can be seen that the length of the 4h part of the actual grown crystal is about 8.6mm, which is highly consistent with the in-situ measurement result. This fully demonstrates the accuracy of the in-situ measurement of crystal resistance and length of the present invention. At the same time, the good crystal quality also shows that the in-situ measurement of crystal resistance and length based on the method and device described in the present invention will not affect the quality of the crystal. Obviously, the invention can be applied to a variety of crystal pulling growth processes, providing great help for the in-situ analysis of the corresponding crystal, which will greatly reduce the process optimization cost of large-size, high-quality crystal growth and promote the progress of the industry.
[0050] Example 4 A system for in-situ characterization of the crystal state during the crystal growth process by the Czochralski method, comprising an electrochemical characterization collection 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 Czochralski crystal growth process, and use a thermometer to record the crystal temperature to obtain the electrochemical impedance spectrum at the growth stage and the corresponding crystal temperature; The simulation calculation device is used to perform equivalent circuit fitting on several electrochemical impedance spectra to obtain the equivalent resistance of the crystal corresponding to each growth stage; based on the equivalent resistance fitted at each growth stage and the corresponding crystal temperature, the corresponding crystal length is calculated and output.
[0051] 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 in-situ characterization of the crystal state during the Czochralski crystal growth process, characterized in that: The specific steps include: During the Czochralski crystal growth process, the impedance between the seed crystal and the crucible containing the melt is measured in real time, and the crystal temperature is recorded using a thermometer to obtain the electrochemical impedance spectrum at this growth stage and its corresponding crystal temperature; Several electrochemical impedance spectra were fitted with equivalent circuits to obtain the equivalent resistance of the crystal corresponding to each growth stage; Based on the equivalent resistance and corresponding crystal temperature fitted at each growth stage, the corresponding crystal length is calculated.
2. The method for in-situ characterization of the crystal state during the Czochralski crystal growth process according to claim 1, characterized in that: During the Czochralski crystal growth process, an electrochemical workstation is used to measure the impedance between the seed crystal and the crucible containing the melt in real time, and a thermometer is used to record the crystal temperature. 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; install the thermocouple of the thermometer on the seed crystal; The Czochralski crystal growth operation is carried out. After the crystal is placed down, the crystal is grown at a constant rotation speed and pulling speed, and the growth diameter of the crystal is monitored in real time. Each time the crystal grows to the set diameter threshold, the impedance spectrum of the growth stage is measured by the electrochemical workstation, and the corresponding crystal temperature is recorded.
3. The method for in-situ characterization of the crystal state during the Czochralski crystal growth process according to claim 2, characterized in that: The impedance between the seed crystal and the crucible containing the melt is measured in real time, and the crystal temperature is recorded by a thermometer, specifically: the counter electrode of the electrochemical workstation is connected to the bottom of the crucible through the first wire; the working electrode and the seed crystal are connected through the second wire; the thermometer and the thermocouple are connected through the third wire; the first wire is led out from the bottom of the crucible by the growth furnace where the Czochralski crystal is grown, and connected to the counter electrode of the electrochemical workstation; the second wire and the third wire are led out from the rotating device of the crystal rotating rod along the crystal rotating rod, and are respectively connected to the working electrode and the thermometer of the electrochemical workstation.
4. The method for in-situ characterization of the crystal state during the Czochralski crystal growth process according to claim 2, characterized in that: Specifically, the connection line of the first wire from the growth furnace to the electrochemical workstation, the connection line of the second wire from the conductive slip ring to the electrochemical workstation, and the connection line of the third wire from the conductive slip ring to the thermometer are all insulated.
5. The method for in-situ characterization of the crystal state during the Czochralski crystal growth process according to claim 2, characterized in that: The impedance between the seed crystal and the crucible containing the melt is measured in real time using an electrochemical workstation. Specifically, either constant current EIS or constant voltage EIS is used. Several measurement scales are selected during the crystal growth stage. The impedance spectrum is measured within a set time period. The crystal is grown with equal diameter using the set parameters. The impedance spectrum is measured with the same parameters every time the crystal is pulled for a period of time.
6. The method for in-situ characterization of the crystal state during the Czochralski crystal growth process according to claim 5, characterized in that: The electrochemical impedance spectrum is fitted with an equivalent circuit. Specifically, the electrochemical impedance spectrum is input into any software such as ZView, ZSimpWin, or CorrView for fitting, thereby extracting the resistance R of the growing crystal. C .
7. The method for in-situ characterization of the crystal state during the Czochralski crystal growth process according to claim 2, characterized in that: If the crystal is grown without flat shoulder during the Czochralski method, the electrochemical impedance spectrum when shoulder placement is completed is also measured and obtained, and the electrochemical impedance spectrum is fitted with an equivalent circuit to obtain the crystal resistance when shoulder placement is completed.
8. The method for in-situ characterization of the crystal state during the Czochralski crystal growth process according to claim 7, characterized in that: Based on the equivalent resistance and corresponding crystal temperature obtained by fitting at each growth stage, the corresponding crystal length is calculated, specifically: If the crystal growth process of the Czochralski method does not adopt the flat shoulder form to grow the crystal, then the resistance value of the crystal at each growth stage obtained by fitting is subtracted from the resistance value of the crystal at the stage of shoulder completion to obtain the resistance value of the equal diameter part of the crystal at each growth stage; According to the corresponding temperature of the crystal at each growth stage, the corresponding resistivity formula is found and its resistivity is calculated; based on the crystal diameter corresponding to each growth stage, the cross-sectional area of the crystal is obtained; according to s / , calculate the length of the crystal at each growth stage; is the resistance of the equal diameter part of the crystal, is the crystal resistivity, is the crystal length, s is the cross-sectional area of the crystal.
9. The method for in-situ characterization of the crystal state during the Czochralski crystal growth process according to claim 2, characterized in that: Based on the equivalent resistance and corresponding crystal temperature obtained by fitting at each growth stage, the corresponding crystal length is calculated, specifically: If the Czochralski method is used to grow crystals in a flat shoulder form, then the corresponding resistivity formula is found and the resistivity is calculated based on the equivalent resistance and corresponding temperature of the crystal at each growth stage; the cross-sectional area of the crystal is obtained based on the crystal diameter corresponding to each growth stage; according to s / , calculate the length of the crystal at each growth stage; is the crystal resistance, is the crystal resistivity, is the crystal length, s is the cross-sectional area of the crystal.
10. A system for in-situ characterization of crystal state during the Czochralski method crystal growth process, 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, and use a thermometer to record the crystal temperature to obtain the electrochemical impedance spectrum at the growth stage and the corresponding crystal temperature; The simulation calculation device is used to perform equivalent circuit fitting on several electrochemical impedance spectra to obtain the equivalent resistance of the crystal corresponding to each growth stage; based on the equivalent resistance fitted at each growth stage and the corresponding crystal temperature, the corresponding crystal length is calculated and output.