Czochralski single crystal growth interface central axis track monitoring system and method based on machine vision

Abstract

The invention discloses a Czochralski single crystal growth interface central axis track monitoring system and method based on machine vision, and belongs to the field of semiconductor material growth. The system comprises a double-view-angle upper furnace cover, an X-view-angle camera, a Y-view-angle camera, a camera clamping device, a filtering-dimming glass interlayer and an image acquisition and analysis system. Wherein the camera is fixed on a corresponding visual angle window of the double-visual-angle upper furnace cover through an angle-adjustable clamp, light in the furnace enters the camera after being processed by the filtering-dimming glass interlayer, and feature point calculation is carried out on images perpendicular to the two visual angles. The system is used for monitoring the central axis position of the single crystal growth interface, can adapt to various thermal field arrangements, and can quickly obtain the central axis position of the single crystal growth interface at each moment, so that the movement track of the single growth interface in a crucible at each moment is accurately reflected, the production efficiency is improved, and the production cost is reduced. And the axis motion trail in the single crystal growth interface can be identified possibly and accurately.

Description

Technical Field

[0001] The invention relates to a machine vision-based central axis trajectory monitoring system and method for a Czochralski single crystal growth interface, belonging to the field of semiconductor material growth. Background Art

[0002] The Czochralski method for producing single crystal silicon is to first melt all the polycrystalline silicon in a quartz crucible, and then contact the rotating seed crystal with the molten polycrystalline silicon liquid surface. A growth interface is formed where the single crystal contacts the silicon melt. A bright energy release ring can be observed in the outermost circle, which looks like a crescent moon in a single perspective and is also called a meniscus. Under a suitable temperature gradient, the seed crystal is pulled upward. During the upward pulling process, both the crystal and the crucible are in a rotating state. The entire thermal field is purged with protective gas. Under the action of the seed crystal, the polycrystalline silicon liquid rearranges the crystals and grows a single crystal on the seed crystal. The single crystals grown by the Czochralski method are generally cylindrical pencil-shaped.

[0003] On the one hand, inert gas is needed to purge the particles volatilized from the melt, and on the other hand, forced convection is generated by the stirring of crucible rotation and crystal rotation, so that the dopant in the melt is evenly distributed. The temperature difference and concentration difference in the melt itself cause natural convection. Therefore, under the joint action of the above multiple factors, during the growth of the crystal, the crystal growth interface is always accompanied by complex movement in the crucible. The main causes are thermal field convection, protective airflow disturbance, vibration of the single crystal pulling mechanism, crystal rotation, crucible rotation system drive, external vibration interference and other factors. The existing technology reduces the amplitude of crystal shaking by pulling the crystal with a soft shaft, building a good shock-absorbing base, reducing the disturbance of the protective purge airflow, and matching the appropriate crystal rotation-crucible rotation growth process. The academic community studies the deterioration conditions of crystal shaking resonance by modeling the single crystal pendulum dynamics model and the rope system modeling, and reduces the amplitude of crystal shaking by introducing magnetic field pulling to reduce natural convection. Studies have shown that when the working speed of the soft shaft crystal pulling system reaches 12-14r / min, obvious resonance will occur, and the resonance point is related to the length of the soft shaft and the mass of the pendulum. Although various fields of industry, academia and research have tried to reduce crystal shaking by optimizing mechanical structures to reduce resonance points, restraints, clamping and other external force conditions, in the complex system of single crystal growth by the Czochralski method, the movement of the growth interface relative to the crucible is inevitable and its movement trajectory is difficult to measure accurately.

[0004] On the one hand, the movement of the crystal growth interface relative to the melt surface will affect the diameter control of the single crystal furnace, and the pulling speed control signal in the single crystal furnace control loop will fluctuate abnormally with the crystal shaking; on the other hand, the movement of the crystal growth interface makes the growth interface at each moment in a different position relative to the crucible, which will cause the transient microscopic diffusion layer of the growth interface to change, thereby causing radial inhomogeneity of the dopant concentration distribution due to the change in the effective segregation coefficient; in addition, the crystal shaking will further intensify the melt convection, causing the solid-liquid interface supercooling to change. Therefore, the movement of the crystal growth interface relative to the melt surface will have an adverse effect on the intrinsic quality of the crystal such as the electrical properties and physical parameters of the single crystal; the process stability such as the single crystal one-time crystallization rate and the single crystal morphology, which is an important factor in the difference between the computer simulation modeling results of the crystal pulling process and the actual production.

[0005] In the process of detecting the single crystal diameter, major manufacturers can only detect the left and right shaking of the crystal parallel to the viewing angle by extracting the left and right vertical contours of the single crystal to calculate the single crystal shaking. Since the water-cooling screen will be added during the crystal pulling process, the viewing angle is narrow and the effective left and right contours of the single crystal cannot be captured. The contour calculation is large, the actual crystal shaking process is highly random, the crystal shaking trajectory cannot be captured under a single viewing angle, and the movement of the single crystal toward the CCD normal direction cannot be captured. The existing technology cannot accurately quantify the instantaneous position of the crystal growth interface in the crucible. It is very important to accurately measure and monitor the crystal growth interface position trajectory, a production phenomenon that seriously affects the quality of single crystals, so as to feed back the accurate crystal growth interface central axis position data to the crystal pulling process modeling, and to provide accurate position parameters for studying the mechanical resonance characteristics of the single crystal furnace and the transient microscopic diffusion layer changes. Summary of the invention

[0006] In view of the above problems existing in the prior art, the purpose of the present invention is to propose a machine vision-based central axis trajectory monitoring system for the CZ single crystal growth interface, which can be used to obtain and analyze images in two perpendicular viewing directions of the crystal pulling process online in real time.

[0007] Another object of the present invention is to provide a method for identifying the center axis position of a single crystal growth interface based on machine vision. By acquiring real-time images in the X and Y directions, the position of the meniscus tip is found to obtain the movement vector of the center in the X and Y directions, and the center point position is mapped to a Cartesian coordinate system, thereby accurately quantifying the center axis trajectory of the single crystal growth interface.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A machine vision-based central axis trajectory system for a CZ single crystal growth interface, the system comprises: a dual-view upper furnace cover, an X-view camera, a Y-view camera, a camera clamping device, a filter-light-reducing glass interlayer, and an image acquisition and analysis system; wherein:

[0010] The double-view upper furnace cover is arranged with two viewing windows, and the side walls of each viewing window are respectively provided with a clamping device installation port and an interlayer installation port. The interlayer installation port is used to install the filter-light-reducing glass interlayer, and the clamping device installation port is used to install the camera clamping device;

[0011] The camera clamping device includes a rotating bracket, an angle marking support plate, and a positioning pin. The X and Y viewing angle cameras are installed on the corresponding rotating brackets. The rotating bracket is movably connected to the angle marking support plate. The angle marking support plate is provided with a movable slot for the rotating bracket to adjust the angle. The angle marking support plate is engraved with degree marks. After adjusting the appropriate camera angle, the rotating bracket is fixed to the angle marking support plate by the positioning pin.

[0012] The light filter-light reduction glass interlayer is installed on the viewing window, between the double-view upper furnace cover and the camera clamping device, and forms an airtight connection with the single crystal furnace chamber; the light filter-light reduction glass interlayer includes a light filter layer and a light reduction layer, the light reduction layer is arranged on the inner side, and the light filter layer is arranged on the outer side; the light filter layer and the light reduction layer are parallel and sealed to form a hollow interlayer;

[0013] The image acquisition and analysis system receives the signal images from the X and Y viewing angle cameras installed on the dual-view upper furnace cover through the signal cables, processes the received images and outputs the results.

[0014] Preferably, the normal directions of the two viewing windows are 90 degrees to each other, and the intersection of the normal lines of the two viewing windows intersects with the three lines of the central axis of the upper furnace cover flange.

[0015] Preferably, a flowing cooling medium is introduced into the hollow interlayer of the light-filtering and light-reducing glass interlayer to cool the light-reducing layer and the light-filtering layer.

[0016] Preferably, the filter-dimming glass sandwich is made of filter glass and dimming glass arranged in parallel with sealant applied all around, the filter layer and the dimming layer are spaced 1-10 mm apart, the filter layer is used to filter out stray light of a specific wavelength, and the dimming layer is used to reduce the intensity of incident light.

[0017] Preferably, the effective pixel value of the photoelectric sensors of the X-viewing angle camera and the Y-viewing angle camera is greater than 5 million pixels.

[0018] Preferably, the lower part of the rotating bracket is movably connected to the movable groove on the angle marking support plate by a roller, and the upper part of the rotating bracket is mechanically connected to the top of the angle marking support plate by a positioning pin. The camera is installed on the rotating bracket and can be adjusted left and right. The camera can follow the rotating bracket to slide in a circle on the angle marking support plate. When it is adjusted to a suitable angle, the positioning pin can be tightened, and the camera viewing angle remains unchanged.

[0019] A method for monitoring the central axis position of a single crystal growth interface using the system comprises the following steps:

[0020] (1) When the material is being processed, adjust the rotating bracket to the appropriate scale and record the data on the angle mark support plate, start the image acquisition and analysis system and input the viewing angle position data into the system;

[0021] (2) Continuously collect X and Y dual-view images in the CZ single crystal furnace, and transmit the collected real-time images in the single crystal furnace to the computer to complete the collection of X and Y dual-view images;

[0022] (3) grayscale the image and select the region of interest (ROI) whose center part covers the meniscus;

[0023] (4) Calculate the maximum value of the gradient in the region of interest and use maximum value suppression to reduce the number of sample points;

[0024] (5) Using the central axis of the ROI area to determine the leftmost and rightmost points with the largest Y value, the unique positions of the left and right corners of the meniscus (Xxl, Xyl), (Xxr, Xyr), (Yxl, Yyl), (Yxr, Yyr) are selected.

[0025] (6) Obtain the center of the left and right vertices of the two viewing angles based on the calculation formula Xo=(Xxl+Xxr)22, Yo=(Yx1+Yxr) / 2; project the center to Cartesian coordinates to obtain the position of the central axis of the single crystal growth interface at that moment as (Xo, Yo).

[0026] Preferably, in step (2), the collected real-time images of the single crystal furnace are transmitted to the computer at a rate of >7FPS.

[0027] The advantages of the present invention are:

[0028] The system for monitoring the central axis of the single crystal growth interface of the present invention is specially designed with a dual-viewing angle monitoring system. The camera is fixed on the dual-viewing angle window by a clamp with an adjustable angle. The light in the furnace enters the camera after being processed by the filter-light-reducing glass interlayer, and the characteristic points of the images of the two vertical viewing angles are calculated. The system of the present invention is used to monitor the central axis position of the single crystal growth interface, which can adapt to various thermal field arrangements, such as the limited viewing angle caused by the arrangement of the water cooling screen, and can very quickly obtain the central axis position of the single crystal growth interface at each moment, thereby accurately reflecting the motion trajectory of the single growth interface in the crucible at each moment, improving production efficiency, and identifying the motion trajectory of the central axis of the single crystal growth interface becomes possible and accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a top view of a dual-view upper furnace cover in the present invention.

[0030] Figure 2 It is a schematic structural diagram of the camera clamping device in the present invention.

[0031] Figure 3 It is a front view of the camera clamping device in the present invention.

[0032] Figure 4 It is a three-dimensional diagram of the double-view upper furnace cover in the present invention.

[0033] Figure 5 The present invention is a flow chart of a method for monitoring the central axis position of a crystal growth interface using the system of the present invention.

[0034] Figure 6 The schematic diagram of the dual-view camera of the present invention for detecting the corner points of the meniscus.

[0035] Figure 7 Schematic diagram of the positions of the left and right corner points of the meniscus obtained from the image viewed from a single camera perspective.

[0036] Figure 8 It is the center point position obtained from the X viewing angle.

[0037] Fig. 9 It is the center point position obtained from the Y perspective.

[0038] Fig.10 It is the trajectory of the central axis of the single crystal growth interface mapped in Cartesian coordinates during the crystal pulling process. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but this does not limit the protection scope of the present invention.

[0040] like Figure 1 As shown, an X-viewing window 2 and a Y-viewing window 3 are arranged on the double-viewing upper furnace cover 1, and a clamping device installation port and an interlayer installation port are respectively provided on the side wall of each viewing window. The interlayer installation port is used to install the filter-light-reducing glass interlayer, and the clamping device installation port is used to install the camera clamping device 4. The X-viewing window 2 and the Y-viewing window 3 are used to observe the furnace from the X and Y directions. The normals of the two viewing windows are 90 degrees to each other, and the intersection of the normals of the two viewing windows intersects with the three lines of the central axis of the upper furnace cover flange.

[0041] In the system of the present invention, the camera clamping devices installed on the X viewing window and the Y viewing window have the same structure, and each camera clamping device clamps two cameras for monitoring the crystal pulling process in the furnace, and the effective pixel value of the photoelectric sensor of the camera is more than 5 million pixels. The camera clamping device includes a rotating bracket, an angle marking support plate, and a positioning pin. The two cameras are installed on the rotating bracket and the relative position between the two cameras can be adjusted left and right; the rotating bracket is movably connected to the angle marking support plate, and the angle marking support plate is provided with a movable slot for the rotating bracket to adjust the angle. The angle marking support plate is engraved with degree marks. After adjusting the appropriate camera angle, the rotating bracket is fixed to the angle marking support plate by the positioning pin.

[0042] As a specific structural example of the camera holding device 4, Figure 2 , 3 As shown, the camera clamping device 4 mainly includes a rotating bracket 41, an angle marking support plate 42, a positioning pin 43, and a mounting plate 44. The angle marking support plate 42 is fixed on the mounting plate 44. The mounting plate 44 is used to install the camera clamping device 4 on the mounting opening of the clamping device on the viewing window. Two cameras 45 are installed on the rotating bracket 41 on the left and right. The rotating bracket 41 is a rectangular frame. The camera 45 can be installed at any position on the long arm of the rotating bracket 41, so that the relative position of the two cameras can be adjusted. A semicircular movable groove is provided on the angle marking support plate 42. The middle part of the lower long arm of the rotating bracket 41 is installed in the movable groove 46 of the angle marking support plate 42 and can slide along the movable groove 46, so that the rotating bracket 41 drives the camera to rotate on the angle marking support plate 42, and the rotation angle range is 0-180°. A positioning pin 43 is provided in the middle of the upper long arm. When the rotating bracket 41 is rotated to a suitable angle, the positioning pin 43 is tightened, and the rotating bracket 41 is fixedly connected to the angle marking support plate 42, thereby realizing free adjustment of the camera angle.

[0043] The filter-light-reducing glass interlayer is installed at the interlayer installation port of the viewing window, between the dual-view upper furnace cover and the camera clamping device, and forms an airtight connection with the single crystal furnace chamber, forming a closed structure to isolate the single crystal furnace from the internal and external environments. The filter-light-reducing glass interlayer is composed of high-temperature resistant polarizing film and coated glass, which are used to filter the light of specific wavelengths in the furnace and reduce the light intensity entering the camera. The selection of polarizing film and light-reducing film matches the spectral response range and peak corresponding wavelength parameters of the camera. Due to the spectral response curve characteristics of the camera itself, and the purpose of acquiring the image is to obtain the meniscus profile, it is preferred that the filter-light-reducing glass interlayer is set according to the wavelength with the best quantum efficiency of the camera so that the light of the wavelength band with the best quantum efficiency can pass with minimal loss while suppressing the light of other wavelength bands, thereby reducing the noise of the collected image and enhancing the area of ​​interest.

[0044] The filter-light-reducing glass sandwich can be made of filter glass and light-reducing glass arranged in parallel and sealed around. The filter layer and the light-reducing layer are spaced 1-10mm apart. The filter layer is used to filter out stray light of a specific wavelength, and the light-reducing layer is used to reduce the intensity of incident light. A flowing cooling medium can also be passed into the hollow interlayer of the filter-light-reducing glass sandwich to cool the light-reducing layer and the filter layer.

[0045] The image acquisition and analysis system consists of a signal cable, a computer, and a computer vision application stored in a readable storage medium. The computer receives the signal image from the X and Y viewing angle cameras installed on the dual-view upper furnace cover through the signal cable. The computer vision application processes the received image and outputs the result.

[0046] In the present invention, X, Y, x, y, l, r, Xx1, Xy1, Xxr, Xyr, Yx1, Yy1, Yxr, Yyr, Xo, and Yo have the following meanings:

[0047] X: X-view image.

[0048] Y: Y perspective image.

[0049] x: Cartesian coordinate system x-axis.

[0050] y: Cartesian coordinate system y-axis.

[0051] 1: represents the abbreviation of the left corner point of the view image (Left).

[0052] r: represents the abbreviation of the right corner point of the viewing angle image (Right).

[0053] Xxl: The x-axis position of the left corner of the meniscus in the X-view camera image.

[0054] Xyl: The y-axis position of the left corner of the meniscus in the X-view camera image.

[0055] Xxr: The x-axis position of the right corner of the meniscus in the X-view camera image.

[0056] Xyr: The y-axis position of the right corner of the meniscus in the X-view camera image.

[0057] Yxl: The x-axis position of the left corner of the meniscus in the Y-view camera image.

[0058] Yyl: Y-axis position of the left corner of the meniscus in the Y-view camera image.

[0059] Yxr: The x-axis position of the right corner of the meniscus in the Y-view camera image.

[0060] Yyr: Y-axis position of the right corner of the meniscus in the Y-view camera image.

[0061] Xo: The x-axis position of the center point in the Cartesian coordinate system obtained by the X-viewing angle.

[0062] Yo: The y-axis position of the center point in the Cartesian coordinate system obtained from the Y perspective.

[0063] like Figure 5 As shown in FIG. 1 , it is a flow chart of a method for monitoring the central axis position of a crystal growth interface using the system of the present invention, as shown in FIG. Figure 6 As shown, it is a principle diagram of the dual-view camera detecting the corner points of the meniscus, wherein the X direction is the X-view camera responsible for collecting the X-direction image signal, and the Y direction is the Y-view camera responsible for collecting the Y-direction image signal. The method for monitoring the central axis position of the crystal growth interface of the present invention comprises the following steps:

[0064] (1) When the material is being processed, adjust the rotating bracket to the appropriate scale and record the data on the angle mark support plate, start the image acquisition and analysis system and input the viewing angle position data into the system.

[0065] (2) Continuously collect X and Y dual-view images in the CZ single crystal furnace, and transmit the collected real-time images in the single crystal furnace to the computer at a rate of >7FPS to complete the collection of X and Y dual-view images.

[0066] (3) graying the image and selecting a region of interest (ROI) whose center part covers the meniscus. The program instructions stored in the computer capture the ROI region of the meniscus at each viewing angle by analyzing the images from the X and Y viewing directions.

[0067] (4) The program instructions stored in the computer calculate the maximum value of the gradient in the region of interest and use maximum value suppression to reduce the number of sample points;

[0068] (5) Using the central axis of the ROI area to determine the leftmost and rightmost points with the largest Y value as a strategy to select the unique left and right corner points of the meniscus; the left corner point of the meniscus is obtained by finding the sample point "extreme left-extreme top", and the right corner point of the meniscus is obtained by finding the sample point "extreme right-extreme top". The positions of the left and right corner points are (Xxl, Xyl), (Xxr, Xyr), (Yx1, Yyl), and (Yxr, Yyr);

[0069] (6) Obtain the center of the two left and right vertices of the two viewing angles based on the calculation formula Xo=(Xxl+Xxr)22, Yo=(Yxl+Yxr) / 2; project the center to Cartesian coordinates to obtain the position of the central axis of the single crystal growth interface at that moment as (Xo, Yo).

[0070] The following is an example of the actual operation process of using this system to monitor the central axis of a crystal growth interface:

[0071] Fix the X and Y viewing angle cameras on the dual-view upper furnace cover, record the viewing angle parameters of the camera on the rotating bracket and the angle mark support plate at this time, start the image acquisition and analysis system, and input the camera viewing angle parameters into the image acquisition and analysis system. At this time, the X and Y viewing angle cameras send the real-time images in the furnace to the image acquisition and analysis system at a frequency of >7FPS. When the meniscus appears after entering the single crystal furnace to complete the seeding, the analysis system starts to process the meniscus images under dual viewing angles in a programmed manner. The program instructions stored in the computer capture the left and right corner points of the meniscus (Xxl, Xyl), (Xxr, Xyr), (Yx1, Yyl), (Yxr, Yyr) through the designed computer image analysis instructions, and then according to the vertex center calculation formula Xo=(Xxl+Xxr) / 2, Yo=(Yx1+Yxr) / 2, the position of the central axis of the single crystal growth interface at this moment is obtained as (Xo, Yo), and refreshed on the display in real time.

[0072] The present invention can accurately measure and monitor the real-time trajectory of the center axis of the CZ single crystal growth interface, meeting the requirements of exploring crystal pulling process modeling, studying the mechanical resonance characteristics of single crystal furnaces, and transient microscopic diffusion layer changes, which need to provide accurate growth interface position parameters.

Claims

1. A central axis trajectory system for the Czochralski single crystal growth interface based on machine vision, characterized in that: The system is equipped with: dual-view upper furnace cover, X-view camera, Y-view camera, camera clamping device, filter-light-reducing glass interlayer, image acquisition and analysis system; The double-view upper furnace cover is arranged with two viewing windows, and the side walls of each viewing window are respectively provided with a clamping device installation port and an interlayer installation port. The interlayer installation port is used to install the filter-light-reducing glass interlayer, and the clamping device installation port is used to install the camera clamping device; The camera clamping device includes a rotating bracket, an angle marking support plate, and a positioning pin. The X and Y viewing angle cameras are installed on the corresponding rotating brackets. The rotating bracket is movably connected to the angle marking support plate. The angle marking support plate is provided with a movable slot for the rotating bracket to adjust the angle. The angle marking support plate is engraved with degree marks. After adjusting the appropriate camera angle, the rotating bracket is fixed to the angle marking support plate by the positioning pin. The light filter-light reduction glass interlayer is installed on the viewing window, between the double-view upper furnace cover and the camera clamping device, and forms an airtight connection with the single crystal furnace chamber; the light filter-light reduction glass interlayer includes a light filter layer and a light reduction layer, the light reduction layer is arranged on the inner side, and the light filter layer is arranged on the outer side; the light filter layer and the light reduction layer are parallel and sealed to form a hollow interlayer; The image acquisition and analysis system receives the signal images from the X and Y viewing angle cameras installed on the dual-view upper furnace cover through the signal cables, processes the received images and outputs the results.

2. The machine vision-based central axis trajectory system for Czochralski single crystal growth interface according to claim 1, characterized in that: The normal directions of the two viewing windows are 90 degrees to each other, and the intersection of the normal lines of the two viewing windows intersects with the three lines of the central axis of the upper furnace cover flange.

3. The machine vision-based central axis trajectory system for Czochralski single crystal growth interface according to claim 1, characterized in that: A flowing cooling medium is introduced into the hollow interlayer of the light filtering-light reducing glass interlayer to cool the light reducing layer and the light filtering layer.

4. The machine vision-based central axis trajectory system for Czochralski single crystal growth interface according to claim 3, characterized in that: The filter-light-reducing glass sandwich is made of filter glass and light-reducing glass arranged in parallel with sealant applied all around. The filter layer and the light-reducing layer are spaced 1-10 mm apart. The filter layer is used to filter out stray light of a specific wavelength, and the light-reducing layer is used to reduce the intensity of incident light.

5. The machine vision-based central axis trajectory system for Czochralski single crystal growth interface according to claim 1, characterized in that: The effective pixel value of the photoelectric sensors of the X-viewing angle camera and the Y-viewing angle camera is more than 5 million pixels.

6. The machine vision-based central axis trajectory system for Czochralski single crystal growth interface according to claim 1, characterized in that: The lower part of the rotating bracket is movably connected to the movable groove on the angle marking support plate by a roller, and the upper part of the rotating bracket is mechanically connected to the top of the angle marking support plate by a positioning pin. The camera is installed on the rotating bracket and can be adjusted left and right. The camera can follow the rotating bracket to slide in a circle on the angle marking support plate. When it is adjusted to a suitable angle, the positioning pin can be tightened, and the camera viewing angle remains unchanged.

7. A method for monitoring the central axis position of a single crystal growth interface using the system according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) When the material is being processed, adjust the rotating bracket to the appropriate scale and record the data on the angle mark support plate, start the image acquisition and analysis system and input the viewing angle position data into the system; (2) Continuously collect X and Y dual-view images in the CZ single crystal furnace, and transmit the collected real-time images in the single crystal furnace to the computer to complete the collection of X and Y dual-view images; (3) grayscale the image and select the region of interest whose center covers the meniscus; (4) Calculate the maximum value of the gradient in the region of interest and use maximum value suppression to reduce the number of sample points; (5) Using the central axis of the region of interest to determine the leftmost and rightmost points with the largest Y value, the unique positions of the left and right corners of the meniscus (Xxl, Xyl), (Xxr, Xyr), (Yxl, Yyl), (Yxr, Yyr) are selected. (6) Obtain the center of the left and right vertices of the two viewing angles based on the calculation formula Xo=(Xxl+Xxr)22, Yo=(Yx1+Yxr) / 2; project the center to Cartesian coordinates to obtain the position of the central axis of the single crystal growth interface at that moment as (Xo, Yo).

8. The method according to claim 7, characterized in that In the step (2), the collected real-time images in the single crystal furnace are transmitted to the computer at a rate of >7FPS.

Images