A method for online detection of a crystal solid-liquid interface

Abstract

This application provides a method for online detection of the solid-liquid interface of a crystal, relating to the technical field of crystal growth. The method discloses that after an incident laser is emitted by a laser emitting module, the reflected laser is received by a laser receiving module. Then, based on the phase difference between the emitted and incident lasers, the optical path length of the laser, and finally the calculated optical path length and the incident angle of the incident laser, the distance between the reflection point on the solid-liquid interface and a preset reference position is determined. Thus, based on the distance between the reflection point on the solid-liquid interface and the preset reference position, the morphology of the solid-liquid interface is determined, achieving the detection of the solid-liquid interface morphology and solving the problem of how to monitor the morphology of the solid-liquid interface of a crystal in real time.

Description

Technical Field

[0001] This application relates to the technical field of crystal growth, and in particular to a method for online detection of the solid-liquid interface in crystals. Background Technology

[0002] Crystal growth is influenced by numerous factors, and the yield rate directly impacts economic benefits. While the Czochralski method allows direct observation of the crystal growth process, the internal quality of the crystal can often only be tested and graded after it exits the furnace. Only then can the parameters for the next batch of crystals be adjusted based on the growth results, a process that is often delayed. Furthermore, according to crystal growth theory, reducing the radial temperature gradient in the melt to create a flat solid-liquid interface leads to the growth of high-quality crystals. Therefore, real-time monitoring of the solid-liquid interface morphology is crucial for crystal growth. Summary of the Invention

[0003] The purpose of this application is to provide a method for online detection of the solid-liquid interface in crystals, thereby solving the problem of how to monitor the morphology of the solid-liquid interface in real time. The specific technical solution is as follows: This application provides a method for online detection of crystal solid-liquid interfaces, the method comprising: Step S1: An incident laser is emitted at a preset incident angle towards the top of the cavity of the seed crystal rod through the laser emission module, so that the incident laser passes through the cavity and is conducted to the crystal to be grown. The seed crystal rod has the cavity arranged along the axial direction, and a pre-made seed crystal is fixed at the bottom end of the seed crystal rod. The crystal to be grown is located below the pre-made seed crystal. Step S2: Receive the reflected laser through the laser receiving module. The reflected laser is obtained by the incident laser being conducted to a reflection point on the solid-liquid interface and then reflected. The solid-liquid interface is the interface between the crystal to be grown and the liquid crystal material. Step S3: Identify the phase difference between the incident laser and the reflected laser; calculate the current optical path using the phase method based on the identified phase difference; calculate the distance between the preset reference position and the reflection point on the solid-liquid interface based on the calculated current optical path, the preset incident angle, and the predetermined conversion relationship, wherein the predetermined conversion relationship is a pre-calibrated relationship between the optical path and the distance between the reflection point on the solid-liquid interface and the preset reference position for different incident angles; Step S4: Adjust the preset incident angle and return to step S1 to continue execution until the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set is obtained; determine the shape of the solid-liquid interface based on the calculated distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set.

[0004] In one possible implementation, identifying the phase difference between the incident laser and the reflected laser, and calculating the current optical path using a phase method based on the identified phase difference, includes: Identify the first phase of the incident laser at the emission time; identify the second phase of the reflected laser at the reception time; Calculate the phase difference between the first phase and the second phase; The current optical path is obtained by calculating the product of the phase difference and the wavelength of light using the phase method, and then dividing it by 2π.

[0005] In one possible implementation, the predetermined conversion relationship includes: the optical path length corresponding to different distances between the reflection point on the solid-liquid interface and the preset reference position at any preset incident angle; The method for determining the predetermined transformation relationship includes: When the incident angle of the incident laser is any preset incident angle in the preset angle set, the distance between the reflection point on the solid-liquid interface and the preset reference position is set to different distances, and the optical path corresponding to different distances is collected. The optical path length is the distance between the reflection point on the solid-liquid interface and the preset reference position when the incident angle of the incident laser is any preset incident angle in the preset angle set.

[0006] In one possible implementation, determining the morphology of the solid-liquid interface based on the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the calculated preset angle set includes: For any preset incident angle in the preset angle set, calculate the coordinates of the reflection point on the solid-liquid interface in the preset coordinate system based on the preset incident angle, the distance between the reflection point on the solid-liquid interface and the preset reference position; Based on the coordinates of the reflection point on the solid-liquid interface in the preset coordinate system corresponding to each preset incident angle in the preset angle set, a three-dimensional geometric model of the crystal to be grown is created. The morphology of the solid-liquid interface is determined based on the three-dimensional geometric model of the crystal to be grown.

[0007] In one possible implementation, determining the morphology of the solid-liquid interface based on the three-dimensional geometric model of the crystal to be grown includes: Based on the three-dimensional geometric model of the crystal to be grown, identify the first diameter at the middle position along the axial direction and the second diameter at both ends along the axial direction of the crystal. Compare the size of the first diameter and the second diameter, and determine whether the solid-liquid interface is concave or convex based on the comparison result.

[0008] In one possible implementation, a prism is disposed between the top end of the cavity of the laser emitting module and the seed crystal rod; The step of emitting incident laser light at a preset incident angle towards the top of the cavity of the seed crystal rod via the laser emission module includes: The laser emission module emits an incident laser beam at the preset incident angle toward the prism; the prism refracts the incident laser beam toward the top of the cavity of the seed crystal rod. Before calculating the distance between the preset reference position and the reflection point on the solid-liquid interface based on the calculated current optical path, the preset incident angle, and the predetermined conversion relationship, the method further includes: Obtain the current rotation angle of the prism; Calculate the preset incident angle based on the current rotation angle.

[0009] In one possible implementation, after calculating the coordinates of the reflection point on the solid-liquid interface in a preset coordinate system based on the preset incident angle, the distance between the reflection point on the solid-liquid interface and a preset reference position, for any preset incident angle in the preset angle set, the method further includes: Obtain the coordinates of the reflection points on the solid-liquid interface in a preset coordinate system at multiple time points; Identify the positions of reflection points on the solid-liquid interface at multiple times in a preset coordinate system, where the coordinates do not change with time, and mark them as defects.

[0010] In one possible implementation, during the growth of the crystal to be grown, the seed crystal rod drives the crystal to be grown to rotate.

[0011] In one possible implementation, a narrow-band filter is disposed between the top of the cavity of the laser receiving module and the seed crystal rod.

[0012] In one possible implementation, the light source of the laser emitting module is a YAG laser with a wavelength of 1064 nm. The narrowband filter is a 1064nm narrowband filter.

[0013] Beneficial effects of the embodiments in this application: This application provides a method for online detection of a crystal solid-liquid interface. The method includes: Step S1, emitting an incident laser at a preset incident angle towards the top of a cavity of a seed crystal rod using a laser emitting module, so that the incident laser passes through the cavity and is conducted to the crystal to be grown, wherein the seed crystal rod has the cavity arranged axially, a pre-made seed crystal is fixed at the bottom end of the seed crystal rod, and the crystal to be grown is located below the pre-made seed crystal; Step S2, receiving a reflected laser using a laser receiving module, wherein the reflected laser is obtained by the incident laser being conducted to a reflection point on the solid-liquid interface and reflected, the solid-liquid interface being the interface between the crystal to be grown and the liquid crystal material; Step S3, identifying the phase difference between the incident laser and the reflected laser; and based on the identified phase difference... The phase difference is calculated using the phase method to obtain the current optical path. Based on the calculated current optical path, the preset incident angle, and the predetermined conversion relationship, the distance between the preset reference position and the reflection point on the solid-liquid interface is calculated. The predetermined conversion relationship is a pre-calibrated relationship between the optical path and the distance between the reflection point on the solid-liquid interface and the preset reference position for different incident angles. In step S4, the preset incident angle is adjusted, and the process returns to step S1 to continue until the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set is obtained. Based on the calculated distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set, the shape of the solid-liquid interface is determined. The present application discloses a method in which an incident laser is emitted by a laser emitting module, and a reflected laser is received by a laser receiving module. Then, the optical path of the laser is calculated based on the phase difference between the emitted and incident lasers. Finally, the distance between the reflection point on the solid-liquid interface and a preset reference position is determined based on the calculated optical path and the incident angle of the incident laser. Thus, the morphology of the solid-liquid interface is determined based on the distance between the reflection point on the solid-liquid interface and the preset reference position, thereby realizing the detection of the morphology of the solid-liquid interface and solving the problem of how to monitor the morphology of the solid-liquid interface of a crystal in real time.

[0014] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0016] Figure 1 A schematic flowchart of a method for online detection of crystal solid-liquid interface provided in an embodiment of this application; Figure 2a A schematic diagram of a detection system corresponding to the online detection method for crystal solid-liquid interface provided in the embodiments of this application; Figure 2b A schematic diagram of another detection system corresponding to the online detection method for crystal solid-liquid interface provided in the embodiments of this application; Figure 3 This application provides a schematic flowchart for calculating the current optical path length in an embodiment of the present application. Figure 4 A schematic flowchart illustrating the process of determining the morphology of the solid-liquid interface, provided in an embodiment of this application. Figure 5 Another flowchart illustrating the determination of the morphology of the solid-liquid interface provided in this application embodiment; Figure 6 A schematic diagram of another detection system corresponding to the online detection method for crystal solid-liquid interface provided in the embodiments of this application; Figure 7 This is a schematic diagram of a process for marking defects provided in an embodiment of this application. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0018] To address the problem of real-time monitoring of the solid-liquid interface morphology of crystals in existing technologies, this application provides a method for online detection of the solid-liquid interface of crystals. The method includes: Step S1, emitting an incident laser at a preset incident angle towards the top of a cavity of a seed crystal rod using a laser emitting module, so that the incident laser passes through the cavity and is conducted to the crystal to be grown. The seed crystal rod has the cavity arranged axially, and a pre-formed seed crystal is fixed at its bottom end. The crystal to be grown is located below the pre-formed seed crystal. Step S2, receiving reflected laser light using a laser receiving module, wherein the reflected laser light is obtained by the incident laser light being conducted to a reflection point on the solid-liquid interface and then reflected. The solid-liquid interface is the interface between the crystal to be grown and the liquid crystal material. Step S3, identifying the phase difference between the incident laser light and the reflected laser light; and based on the identified phase difference... The position difference is calculated using the phase method to obtain the current optical path. Based on the calculated current optical path, the preset incident angle, and the predetermined conversion relationship, the distance between the preset reference position and the reflection point on the solid-liquid interface is calculated. The predetermined conversion relationship is a pre-calibrated relationship between the optical path and the distance between the reflection point on the solid-liquid interface and the preset reference position for different incident angles. In step S4, the preset incident angle is adjusted, and the process returns to step S1 to continue until the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set is obtained. Based on the calculated distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set, the shape of the solid-liquid interface is determined.

[0019] The present application discloses a method in which an incident laser is emitted by a laser emitting module, and a reflected laser is received by a laser receiving module. Then, the optical path of the laser is calculated based on the phase difference between the emitted and incident lasers. Finally, the distance between the reflection point on the solid-liquid interface and a preset reference position is determined based on the calculated optical path and the incident angle of the incident laser. Thus, the morphology of the solid-liquid interface is determined based on the distance between the reflection point on the solid-liquid interface and the preset reference position, thereby realizing the detection of the morphology of the solid-liquid interface and solving the problem of how to monitor the morphology of the solid-liquid interface of a crystal in real time.

[0020] Specifically, this application first provides a method for online detection of the solid-liquid interface of a crystal, see [link to relevant documentation]. Figure 1 , Figure 1 A schematic flowchart of a method for online detection of crystal solid-liquid interface provided in an embodiment of this application, the method comprising: Step S1: An incident laser is emitted at a preset incident angle towards the top of the cavity of the seed crystal rod through the laser emission module, so that the incident laser passes through the cavity and is conducted to the crystal to be grown. The seed crystal rod has the cavity arranged along the axial direction, and a pre-made seed crystal is fixed at the bottom end of the seed crystal rod. The crystal to be grown is located below the pre-made seed crystal. Step S2: Receive the reflected laser through the laser receiving module. The reflected laser is obtained by the incident laser being conducted to a reflection point on the solid-liquid interface and then reflected. The solid-liquid interface is the interface between the crystal to be grown and the liquid crystal material. Step S3: Identify the phase difference between the incident laser and the reflected laser; calculate the current optical path using the phase method based on the identified phase difference; calculate the distance between the preset reference position and the reflection point on the solid-liquid interface based on the calculated current optical path, the preset incident angle, and the predetermined conversion relationship, wherein the predetermined conversion relationship is a pre-calibrated relationship between the optical path and the distance between the reflection point on the solid-liquid interface and the preset reference position for different incident angles; Step S4: Adjust the preset incident angle and return to step S1 to continue execution until the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set is obtained; determine the shape of the solid-liquid interface based on the calculated distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set.

[0021] Corresponding to step S1 above, the seed crystal rod has a cavity along its axial direction, and a pre-made seed crystal is fixed at the bottom end of the seed crystal rod. The crystal to be grown is located below the pre-made seed crystal. In actual use, before loading the furnace, the top of the pre-made seed crystal is optically polished and coated with an anti-reflection film, and then fixed to the bottom of the seed crystal rod, so as to facilitate the laser entering the pre-made seed crystal during subsequent detection. It should be noted that the solution of this application is applied to the process of manufacturing crystals by the Czochralski method, also known as the Chuklaski method, which can pull high-quality single crystals from the melt and can be used to grow colorless sapphire, ruby, yttrium aluminum garnet, gadolinium gallium garnet, alexandrite, and spinel. When growing crystals, the raw materials constituting the crystal can be placed in a crucible and heated to melt. The pre-made seed crystal is attached to the surface of the melt and the melt is pulled up. Under controlled conditions, the seed crystal and the melt are continuously rearranged at the interface, and the crystal is gradually grown as the temperature drops and solidifies, which is the crystal to be grown mentioned in this application.

[0022] See Figure 2a , Figure 2aThis is a schematic diagram of a detection system corresponding to the online detection method for the solid-liquid interface of a crystal provided in this application embodiment. The detection system includes a laser emitting module, a laser receiving module, and a pre-formed seed crystal and a crystal to be grown at the bottom of a seed crystal rod. The pre-formed seed crystal can be T-shaped, and the seed crystal rod is a hollow tubular structure that matches the size of the pre-formed seed crystal, thereby fixing the pre-formed seed crystal. In a preferred embodiment, a circular light guide rod, made of quartz material, can be disposed above the pre-formed seed crystal inside the seed crystal rod. This light guide rod guides the laser emitted by the laser emitting module located outside the furnace to the seed crystal. It should be noted that the preset incident angles in this application are multiple predetermined angles. In one possible implementation, the light source of the laser emitting module is a YAG (yttrium aluminum garnet) laser with a wavelength of 1064 nm.

[0023] Corresponding to step S2 above, the reflected laser is obtained by the incident laser being conducted to a reflection point on the solid-liquid interface and then reflected. The solid-liquid interface is the interface between the crystal to be grown and the liquid crystal material. The incident laser irradiates the pre-made seed crystal through the hollow seed crystal rod. Since the pre-made seed crystal and the crystal to be grown are integrated, the laser will enter the crystal to be grown. At the same time, because the optical crystal of the crystal to be grown has good light transmittance, the laser loss inside the crystal to be grown is small. During the laser's propagation, it will be reflected when it encounters impurities, defects, and the solid-liquid interface. When impurities are involved, the intensity of the reflection is also related to the defect level. In one example, when the reflected laser is received by a laser receiving module, the laser receiving module may include an optical receiving module, a photodetector, and a signal amplifier. The laser receiving module can receive the laser signal and convert it into an electrical signal, thereby facilitating the acquisition and analysis of phase and other characteristics based on the electrical signal.

[0024] Corresponding to step S3 above, the predetermined conversion relationship is a pre-calibrated conversion relationship between the optical path length and the distance between the reflection point on the solid-liquid interface and the preset reference position at different incident angles. In one possible implementation, the predetermined conversion relationship includes: the optical path length corresponding to different distances between the reflection point on the solid-liquid interface and the preset reference position at any preset incident angle; the method for determining the predetermined conversion relationship includes: when the incident angle of the incident laser is any preset incident angle in the preset angle set, setting the distance between the reflection point on the solid-liquid interface and the preset reference position to different distances respectively, and collecting the optical path length corresponding to different distances; based on the collected optical path length corresponding to different distances between the reflection point on the solid-liquid interface and the preset reference position when the incident angle of the incident laser is any preset incident angle in the preset angle set. In practical applications, due to the small cavity of the seed crystal rod, the selectable incident angles are limited. Therefore, this application employs a method of creating a preset angle set. First, multiple selectable incident angles are set, and then calibration is performed for each incident angle to determine the conversion relationship through an exhaustive method. Specifically, during the calibration process, for each incident angle, the optical path of the laser is detected at different distances between the reflection point on the solid-liquid interface and the preset reference position. In practical applications, after determining the optical path corresponding to different distances between the reflection point on the solid-liquid interface and the preset reference position at any preset incident angle, a corresponding relationship can be fitted. The fitting method can be found in existing technologies, which will not be elaborated upon here. When identifying the phase difference between the incident laser and the reflected laser, the phase of the incident laser and the phase of the reflected laser can be acquired to calculate the phase difference. In one example, when emitting a laser, the phase of the modulated laser is the same; therefore, only the phase of the reflected laser needs to be acquired to calculate the phase difference. After calculating the current optical path using the phase method based on the identified phase difference, the distance between the preset reference position and the reflection point on the solid-liquid interface can be calculated based on the calculated current optical path, the preset incident angle, and the pre-determined transformation relationship. Specifically, the distance between the preset reference position and the reflection point on the solid-liquid interface can be determined by searching based on the current optical path, the preset incident angle, and the pre-determined transformation relationship. If the reference position does not exist, the closest one can be selected as the current search result. See the example below. Figure 2b , Figure 2bThis diagram illustrates another detection system corresponding to the online detection method for the solid-liquid interface of a crystal provided in this application. Before crystal growth, when the seed crystal is above the liquid, light can be incident perpendicularly. The distance to the bottom of the seed crystal can then be measured based on the reflected wave. Since the seed crystal is intact at this point, its actual position is known, allowing for initial calibration. After the initial calibration, the laser can be tilted at multiple angles. Different angles will result in different distance values ​​at the bottom of the seed crystal, which is essentially a result of optical path extension. During calibration, the data from each angle can be calibrated and verified separately. In practical use, the laser receiving module should have a sufficient detection range to detect reflected laser light from multiple angles.

[0025] Corresponding to step S4 above, the preset incident angle is adjusted, and the process returns to step S1 to continue until the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set is obtained. This step is an iterative process, calculating the distance for each preset incident angle to obtain the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to all incident angles. This facilitates determining the shape of the solid-liquid interface based on the calculated distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set. In this application, the preset reference position can be the emission port of the laser emission module or other preset positions. In one example, the distance between the reflection point on the solid-liquid interface and the preset reference position can be the straight-line distance between the reflection point on the solid-liquid interface and the emission port of the laser emission module, or the broken-line distance after reflection. For details, please refer to the description of the following embodiments. Specifically, after obtaining multiple distances, a three-dimensional model can be created to determine the shape of the solid-liquid interface based on the model. Specifically, the shape can refer to a concave shape or a convex shape. It should be noted that during the actual testing process, temperature will affect the refractive index. This effect can be corrected by algorithms. For specific correction methods, please refer to the prior art. This application will not elaborate on this.

[0026] As can be seen, the solution disclosed in this application involves emitting an incident laser through a laser emitting module, receiving the reflected laser through a laser receiving module, calculating the optical path of the laser based on the phase difference between the emitted and incident lasers, and finally determining the distance between the reflection point on the solid-liquid interface and a preset reference position based on the calculated optical path and the incident angle of the incident laser. Thus, the morphology of the solid-liquid interface is determined based on the distance between the reflection point on the solid-liquid interface and the preset reference position, thereby realizing the detection of the morphology of the solid-liquid interface and solving the problem of how to monitor the morphology of the solid-liquid interface of a crystal in real time.

[0027] In one possible implementation, the phase difference between the incident laser and the reflected laser is identified; the current optical path is calculated based on the identified phase difference using a phase method, see [link to relevant documentation]. Figure 3 , Figure 3 A flowchart illustrating the calculation of the current optical path provided in this application embodiment includes: Step S21: Identify the first phase of the incident laser at the emission time; identify the second phase of the reflected laser at the reception time; Step S22: Calculate the phase difference between the first phase and the second phase; Step S23: Calculate the ratio of the product of the phase difference and the wavelength of light to 2π using the phase method to obtain the current optical path.

[0028] In practical applications, the phase of the incident laser can be modulated to match the phase of the emitted laser. Therefore, only the phase of the reflected laser needs to be detected to determine the phase difference based on the predetermined phase of the incident laser. Alternatively, phase modulation can be omitted, and the phase of the incident laser at the time of emission can be directly detected to obtain the first phase. To identify the second phase of the reflected laser at the moment of reception, an optical receiving module can receive the reflected laser, followed by photoelectric conversion using a photodetector, amplification by a signal amplifier, and phase detection using an oscilloscope or similar device to obtain the second phase. In one example, the laser emitting module and laser receiving module in this application are sub-modules in a laser ranging device.

[0029] In one example, the current optical path is obtained by calculating the product of the phase difference and the wavelength of light using the phase method, and then dividing it by 2π. Specifically, this can be achieved using the formula: The calculation is performed, where Δ represents the optical path length, with units consistent with the wavelength, in meters or nanometers, and λ represents the wavelength of light in a vacuum. This indicates the phase difference, expressed in radians (rad).

[0030] In one possible implementation, the morphology of the solid-liquid interface is determined by the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the calculated preset angle set. (See also...) Figure 4 , Figure 4 A flowchart illustrating the determination of the morphology of the solid-liquid interface provided in this application embodiment includes: Step S31: For any preset incident angle in the preset angle set, calculate the coordinates of the reflection point on the solid-liquid interface in the preset coordinate system based on the preset incident angle, the distance between the reflection point on the solid-liquid interface and the preset reference position; Step S32: Based on the coordinates of the reflection point on the solid-liquid interface in the preset coordinate system corresponding to each preset incident angle in the preset angle set, create a three-dimensional geometric model of the crystal to be grown. Step S33: Determine the morphology of the solid-liquid interface based on the three-dimensional geometric model of the crystal to be grown.

[0031] Specifically, for any preset incident angle in the preset angle set, based on the preset incident angle and the distance between the reflection point on the solid-liquid interface and the preset reference position, the coordinates of the reflection point on the solid-liquid interface in the preset coordinate system can be calculated. This allows for the calculation of the coordinates of the reflection point on the solid-liquid interface in a coordinate system with the laser emitter as the origin, thereby constructing a three-dimensional geometric model based on the calculated coordinates. In one example, the distance between the reflection point on the solid-liquid interface and the preset reference position can be the straight-line distance between the reflection point on the solid-liquid interface and the emission port of the laser emission module. Specifically, based on the coordinates of the reflection point on the solid-liquid interface in the preset coordinate system corresponding to each preset incident angle in the preset angle set, a spherical coordinate system can be created. This spherical coordinate system can represent the coordinate system position of the reflection point on the solid-liquid interface. Then, through the transformation relationship between the spherical coordinate system and the Cartesian coordinate system, the coordinates of the reflection point on the solid-liquid interface in the Cartesian coordinate system are calculated. Based on the coordinates of the reflection points on the solid-liquid interface in a preset coordinate system corresponding to each preset incident angle in the preset angle set, a three-dimensional geometric model of the crystal to be grown is created. This can be achieved using the principle of coordinate point imaging to create the solid-liquid interface model. Since this interface represents the boundary of the crystal to be grown, its three-dimensional geometric structure can be determined. In one example, when creating the three-dimensional geometric model of the crystal to be grown, any two adjacent reflection points can be connected to fit the solid-liquid interface, thereby determining the three-dimensional geometric structure of the crystal.

[0032] In one possible implementation, the morphology of the solid-liquid interface is determined based on the three-dimensional geometric model of the crystal to be grown, see [reference needed]. Figure 5 , Figure 5 Another flowchart illustrating the determination of the morphology of the solid-liquid interface provided in this application embodiment includes: Step S41: Based on the three-dimensional geometric model of the crystal to be grown, identify the first diameter at the middle position along the axial direction and the second diameter at both ends along the axial direction of the crystal to be grown. Step S42: Compare the size of the first diameter and the second diameter, and determine whether the solid-liquid interface is concave or convex based on the comparison result.

[0033] Specifically, the convex morphology refers to a solid-liquid interface where the center bulges towards the liquid phase (i.e., the interface appears "bulge" when viewed from inside the crystal). This morphology is common in growth environments with large radial temperature gradients, leading to a relatively slow growth rate at the crystal center, resulting in high impurity concentration at the center and low concentration at the edges, and potentially increased dislocation density at the center. The concave morphology refers to a solid-liquid interface where the center is recessed towards the solid phase (i.e., the interface appears "bowl-shaped" when viewed from inside the crystal). In this morphology, the crystal edge grows relatively quickly, easily leading to high impurity concentration at the edges and low concentration at the center. If the curvature is too large, it can easily cause inclusion defects. Therefore, in this application, the interface during crystal growth is detected. Specifically, based on the three-dimensional geometric model of the crystal to be grown, the first diameter at the middle position along the axial direction and the second diameter at both ends along the axial direction are identified. Then, the sizes of the first and second diameters are compared, and the morphology of the solid-liquid interface is determined to be either concave or convex based on the comparison result. That is, when the first diameter is smaller than the second diameter, it is a concave morphology; when the first diameter is larger than the second diameter, it is a convex morphology. In practical applications, when a convex shape is determined, the difference between the first and second diameters can be calculated to further determine whether the solid-liquid interface is slightly convex or excessively convex. If the difference exceeds a preset threshold, it is determined to be excessively convex. Since excessive convexity can also affect crystal growth, it also needs to be detected.

[0034] In one possible implementation, a prism is disposed between the laser emitting module and the top of the cavity of the seed crystal rod; the emission of incident laser light at a preset incident angle through the laser emitting module includes: emitting incident laser light at the prism through the laser emitting module at the preset incident angle; refracting the incident laser light towards the top of the cavity of the seed crystal rod through the prism; before calculating the distance between the preset reference position and the reflection point on the solid-liquid interface based on the calculated current optical path, the preset incident angle, and a predetermined conversion relationship, the method further includes: obtaining the current rotation angle of the prism; and calculating the preset incident angle based on the current rotation angle. Specifically, the prism allows for further control of the laser's incident angle, and the laser's incident angle can be calculated and adjusted based on the current rotation angle of the prism. In practical use, the angle at which the laser emitter emits laser light can be fixed, and the incident angle can be adjusted only by adjusting the rotation angle of the prism, and the incident angle can be determined based on the rotation angle. In practical use, the laser incident angle can be pre-calibrated by measuring the laser's incident angle under different prism rotation angles. This establishes a correspondence between the prism rotation angle and the laser incident angle. Further, when calculations are needed, the laser incident angle can be calculated based on this correspondence and the prism rotation angle. However, it should be noted that in this application, before calculating the distance between the preset reference position and the reflection point on the solid-liquid interface based on the calculated current optical path, the preset incident angle, and the predetermined conversion relationship, the preset incident angle and the predetermined conversion relationship are used. In practical applications, the prism rotation angle can be directly selected, and a prism rotation angle and the predetermined conversion relationship can be created. Then, in later calculations, the distance between the preset reference position and the reflection point on the solid-liquid interface can be calculated using this prism rotation angle. Further, see... Figure 6 , Figure 6This is a schematic diagram of another detection system corresponding to the online detection method for the solid-liquid interface of a crystal provided in the embodiments of this application. The system includes a laser emitting module, a laser receiving module, a seed crystal rod, and the crystal to be grown, as well as a prism. In the scheme of this application, the laser is located outside the crystal furnace. To measure more information, the incident angle is adjustable. In one example, the light path undergoes total internal reflection via a light guide rod, allowing leakage-free transmission into the seed crystal. Furthermore, by adjusting the reflection angle, the light reaches more locations, and the distance traveled by the light path is extended. When calculating the distance between the preset reference position and the reflection point on the solid-liquid interface, multiple selectable incident angles can still be set, and then calibrated for each incident angle. This exhaustive method determines the conversion relationship, and based on the calculated current optical path, the preset incident angle, and the predetermined conversion relationship, the distance between the preset reference position and the reflection point on the solid-liquid interface is calculated. Since this conversion relationship is obtained through calibration, the distance between the reflection point on the solid-liquid interface and the emission port of the laser emitting module can also be used as the preset reference position and the solid-liquid interface. Specifically, during calibration, calibration can be performed for different preset incident angles, given the known distance between a preset reference position and the solid-liquid interface. Finally, for any preset incident angle from the preset angle set, when calculating the coordinates of the reflection point on the solid-liquid interface in a preset coordinate system based on the preset incident angle, the distance between the reflection point on the solid-liquid interface and the preset reference position, a pre-calibration method can be used to pre-determine the correspondence between the preset incident angle, the distance between the reflection point on the solid-liquid interface and the preset reference position, and the coordinates of the reflection point on the solid-liquid interface in the preset coordinate system. This determines the coordinates of the reflection point on the solid-liquid interface to be calculated in the preset coordinate system, thus facilitating the determination of the solid-liquid interface morphology using the scheme described in the above embodiments.

[0035] In one possible implementation, after calculating the coordinates of the reflection point on the solid-liquid interface in a preset coordinate system based on the preset incident angle, the distance between the reflection point on the solid-liquid interface and a preset reference position, for any preset incident angle in the preset angle set, see [link to relevant documentation]. Figure 7 , Figure 7 This application provides a flowchart illustrating a method for marking defects, which further includes: Step S51: Obtain the coordinates of the reflection points on the solid-liquid interface in a preset coordinate system at multiple time points; Step S52: Identify the positions of the reflection points on the solid-liquid interface at multiple times in a preset coordinate system, where the coordinates do not change with time, and mark them as defects.

[0036] In one example, the solution of this application is based on a phase-type laser rangefinder, which can achieve micron-level measurement accuracy over short distances. The rangefinder is located outside the crystal growth furnace. Under normal circumstances, the crystal quality is good, and the light path only reflects when it reaches the solid-liquid interface. A typical solid-liquid interface is not flat at the microscopic level but has slight undulations, causing the laser to reflect in various directions, with some of the laser returning along its original path. After receiving the reflected laser, the distance value of the reflection point is output, and the position data is continuously input into the computer, thereby achieving continuous distance measurement. Since the coordinates of the reflection point on the solid-liquid interface change with the crystal growth process, while the coordinates of impurities and other defects in the crystal do not change, the position of the reflection point on the solid-liquid interface at multiple moments in a preset coordinate system, where the coordinates do not change with time, can be identified and marked as a defect. In one example, during the crystal growth stage, the pre-formed seed crystal has been submerged in the liquid crystal, and the main echo of the laser reflection will be the solid-liquid interface. Multi-angle measurements can be performed, and the position of the light path reaching the solid-liquid surface will be different at different angles, thus obtaining more information about the solid-liquid interface. Then, the measurement information is processed to plot the actual position of the solid-liquid interface. Specifically, when collecting reflection signals caused by crystal defects and filtering data, in addition to the solid-liquid interface, large defects within the crystal can also cause laser reflection. As the crystal grows, the position of the defects within the crystal remains unchanged, while the position of the solid-liquid interface continuously changes, and its distance is close to the length of the crystal growth. Thus, the two can be distinguished. Through the scheme of this application, a computer can be used to reconstruct the crystal situation after collecting laser ranging information. For the same defect, the output value of the laser rangefinder will differ due to the different optical paths when measured at different angles. The position information can be integrated using an algorithm. During integration, the calibration values ​​calibrated at each angle can be used. At the same laser angle, the optical path is the same, so the measurement values ​​at different angles can be normalized. Secondly, the position of the defect within the crystal remains unchanged during integration, thus allowing for verification of the normalized data. In one possible implementation, during the growth process of the crystal to be grown, the seed crystal rod drives the crystal to be grown to rotate. This facilitates the identification of defects in different orientations of the crystal. It is also important to note that the rotation of the crystal to be grown will affect the optical path. Excessive rotation speed may lead to optical path instability; typically, the rotation speed is 5-60 rpm. In the scheme of this application, the rotation speed can be reduced within this range to minimize the impact on optical path stability. In one possible implementation, a narrow-band filter is provided between the laser receiving module and the top of the cavity of the seed crystal rod. In actual use, the optical path experiences partial light reflection at each interface it passes through, such as the interface between the light guide rod and air, the interface between air and the seed crystal, the solid-liquid interface of the crystal, and the light reflected back from the bottom of the crucible after the laser strikes it.In this application, the reflected light from the solid-liquid interface needs to be collected. To improve the signal-to-noise ratio, a filter matching the laser wavelength is installed in the optical path of the system. This filter can significantly reduce light pollution caused by high temperatures in the crystal furnace, while having minimal attenuation of laser light at specific frequencies. In this application, antireflection films matching the laser wavelength can also be deposited at both ends of the light guide rod and on the top of the seed crystal. In one example, the narrowband filter is a 1064nm filter. Narrowband filters are optical elements subdivided from bandpass filters. They allow light signals to pass through in a specific wavelength band while suppressing interference light deviating from the band. Their passband width is generally less than 5% of the center wavelength value, and can be as low as 2nm. Therefore, the filter can filter light, prevent interference, and improve the detection efficiency of the crystal. It should be noted that in actual detection, the marked defects may not cover all defects, but the solution in this application does achieve defect detection, which has important reference value for actual production.

[0037] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0038] The various embodiments in this specification are described in a related manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments. For related parts, please refer to the description of the method embodiment.

[0039] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A method for in-line detection of a crystal solid-liquid interface, characterized in that, The method includes: Step S1: An incident laser is emitted at a preset incident angle towards the top of the cavity of the seed crystal rod through the laser emission module, so that the incident laser passes through the cavity and is conducted to the crystal to be grown. The seed crystal rod has the cavity arranged along the axial direction, and a pre-made seed crystal is fixed at the bottom end of the seed crystal rod. The crystal to be grown is located below the pre-made seed crystal. Step S2: Receive the reflected laser through the laser receiving module. The reflected laser is obtained by the incident laser being conducted to a reflection point on the solid-liquid interface and then reflected. The solid-liquid interface is the interface between the crystal to be grown and the liquid crystal material. Step S3: Identify the phase difference between the incident laser and the reflected laser; calculate the current optical path using the phase method based on the identified phase difference; calculate the distance between the preset reference position and the reflection point on the solid-liquid interface based on the calculated current optical path, the preset incident angle, and the predetermined conversion relationship, wherein the predetermined conversion relationship is a pre-calibrated relationship between the optical path and the distance between the reflection point on the solid-liquid interface and the preset reference position for different incident angles; Step S4: Adjust the preset incident angle and return to step S1 to continue execution until the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set is obtained; determine the shape of the solid-liquid interface based on the calculated distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the preset angle set.

2. The method of claim 1, wherein, The process of identifying the phase difference between the incident laser and the reflected laser, and calculating the current optical path using the phase method based on the identified phase difference, includes: Identify the first phase of the incident laser at the emission time; identify the second phase of the reflected laser at the reception time; Calculate the phase difference between the first phase and the second phase; The current optical path is obtained by calculating the product of the phase difference and the wavelength of light using the phase method, and then dividing it by 2π.

3. The method of claim 1, wherein, The predetermined conversion relationship includes: the optical path length corresponding to different distances between the reflection point on the solid-liquid interface and the preset reference position at any preset incident angle; The method for determining the predetermined transformation relationship includes: When the incident angle of the incident laser is any preset incident angle in the preset angle set, the distance between the reflection point on the solid-liquid interface and the preset reference position is set to different distances, and the optical path corresponding to different distances is collected. The optical path length is the distance between the reflection point on the solid-liquid interface and the preset reference position when the incident angle of the incident laser is any preset incident angle in the preset angle set.

4. The method according to claim 1, characterized in that, The step of determining the morphology of the solid-liquid interface based on the distance between the reflection point on the solid-liquid interface and the preset reference position corresponding to each preset incident angle in the calculated preset angle set includes: For any preset incident angle in the preset angle set, calculate the coordinates of the reflection point on the solid-liquid interface in the preset coordinate system based on the preset incident angle, the distance between the reflection point on the solid-liquid interface and the preset reference position; Based on the coordinates of the reflection point on the solid-liquid interface in the preset coordinate system corresponding to each preset incident angle in the preset angle set, a three-dimensional geometric model of the crystal to be grown is created. The morphology of the solid-liquid interface is determined based on the three-dimensional geometric model of the crystal to be grown.

5. The method according to claim 1, characterized in that, Determining the morphology of the solid-liquid interface based on the three-dimensional geometric model of the crystal to be grown includes: Based on the three-dimensional geometric model of the crystal to be grown, identify the first diameter at the middle position along the axial direction and the second diameter at both ends along the axial direction of the crystal. Compare the size of the first diameter and the second diameter, and determine whether the solid-liquid interface is concave or convex based on the comparison result.

6. The method according to claim 3, characterized in that, A prism is provided between the top of the cavity of the laser emitting module and the seed crystal rod; The step of emitting incident laser light at a preset incident angle to the top of the cavity of the seed crystal rod via the laser emitting module includes: The laser emission module emits an incident laser beam at the preset incident angle toward the prism; the prism refracts the incident laser beam toward the top of the cavity of the seed crystal rod. Before calculating the distance between the preset reference position and the reflection point on the solid-liquid interface based on the calculated current optical path, the preset incident angle, and the predetermined conversion relationship, the method further includes: Obtain the current rotation angle of the prism; Calculate the preset incident angle based on the current rotation angle.

7. The method according to claim 4, characterized in that, After calculating the coordinates of the reflection point on the solid-liquid interface in a preset coordinate system based on the preset incident angle, the distance between the reflection point on the solid-liquid interface and the preset reference position, for any preset incident angle in the preset angle set, the method further includes: Obtain the coordinates of the reflection points on the solid-liquid interface in a preset coordinate system at multiple time points; Identify the positions of reflection points on the solid-liquid interface at multiple times in a preset coordinate system, where the coordinates do not change with time, and mark them as defects.

8. The method according to claim 1, characterized in that, During the growth of the crystal to be grown, the seed crystal rod drives the crystal to be grown to rotate.

9. The method according to claim 1, characterized in that, A narrow-band filter is provided between the top of the cavity of the laser receiving module and the seed crystal rod.

10. The method according to claim 9, characterized in that, The light source of the laser emitting module is a YAG laser, and the wavelength of the YAG laser is 1064nm; The narrowband filter is a 1064nm narrowband filter.

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