Automatic temperature control method for crystal growth device, system, and device

Abstract

An automatic temperature control method for a crystal growth device, a system, and a device. The method is used for a crystal growth device. The crystal growth device comprises a main control heating body and an auxiliary control heating body, wherein the main control heating body is used for controlling a high-temperature interval of the growth device, and the auxiliary control heating body is used for controlling a low-temperature interval of the growth device. The automatic temperature control method comprises: acquiring a growth parameter of a crystal growth solid-liquid interface, wherein the growth parameter is used for representing the growth state of a crystal; calculating a temperature adjustment amount for the main control heating body on the basis of the offset of the growth parameter by using a first multi-stage automatic temperature control algorithm, and calculating a temperature difference adjustment amount for the auxiliary control heating body and the main control heating body on the basis of the offset of the growth parameter by using a second multi-stage automatic temperature control algorithm; and adjusting the main control heating body on the basis of the temperature adjustment amount for the main control heating body, and adjusting the auxiliary control heating body on the basis of the temperature adjustment amount for the main control heating body and the temperature difference adjustment amount for the auxiliary control heating body and the main control heating body.

Description

Automatic temperature control methods, systems, and apparatus for crystal growth apparatus Technical Field

[0001] This invention relates to the field of single crystal growth technology, specifically to an automatic temperature control method, system, and apparatus for crystal growth devices, and particularly to the growth and preparation of large-size fluoride crystals using a crucible descent method. Background Technology

[0002] In the melt growth process of crystals, the success and quality of crystal growth are determined by the ideality of the solid-liquid interface, which in turn is determined by the temperature distribution of the growth zone, i.e., the thermal field. For example, in the preparation of large-size fluoride optical crystals using the crucible lowering method, the key to the crystal growth result lies in the control of the solid-liquid interface. Ideally, the solid-liquid interface should be located within the temperature gradient range and maintain a slightly convex morphology (observed from the crystal towards the melt). Therefore, real-time acquisition of information about the solid-liquid interface and adjustment of crystal growth control parameters based on the interface's state feedback are crucial for crystal growth. However, contamination from water, oxygen, and other components in the growth atmosphere must be strictly avoided during fluoride crystal growth to prevent the adverse effects of oxygen-containing impurities. Therefore, when preparing large-size fluoride optical crystals using the crucible lowering method, the entire crystal growth process must be carried out in a high-vacuum furnace, typically made of stainless steel. Because the fluoride melt is sealed inside a graphite crucible, and the graphite crucible and surrounding insulation material are sealed within a stainless steel cavity, the growth process of the fluoride optical crystal is actually completed in an unobservable "black box." Therefore, when using the crucible lowering method to prepare large-size fluoride optical crystals, the position and shape information of the solid-liquid interface during crystal growth inside the crucible are completely lost. This makes it impossible to provide feedback for process optimization, and also makes it difficult to control parameters such as temperature in real time during the preparation process.

[0003] Due to the lack of information regarding the location and shape of the solid-liquid interface during crystal growth, the optimization of existing fluoride optical crystal fabrication processes heavily relies on the experience of crystal growth personnel, largely depending on continuous trial and error to gradually optimize parameters such as temperature control. However, as the size of fluoride optical crystals increases, the difficulty of this process exploration increases dramatically. More importantly, with the increase in crystal aperture, it is necessary to use multiple heating elements for independent temperature control to construct the temperature field required for large-size crystal growth. This significantly increases the variables controlling crystal growth, further increasing the economic and time costs of the trial-and-error method. Therefore, achieving automatic temperature control at the solid-liquid interface during crystal growth is crucial for breakthroughs in the fabrication technology of large-size fluoride optical crystals. Summary of the Invention

[0004] A first aspect of the present invention provides an automatic temperature control method for a crystal growth apparatus, the automatic temperature control method comprising: acquiring growth parameters of a solid-liquid interface for crystal growth, the growth parameters being used to characterize the growth state of the crystal, the growth parameters including interface position parameters and interface curvature parameters, the interface position parameter being the position of the vertex of the solid-liquid interface in the crystal growth direction, and the interface curvature parameter being the quotient of the height difference between the vertex and the edge of the solid-liquid interface in the crystal growth direction and the crystal diameter; calculating a temperature adjustment amount of a main control heating element based on the offset of the interface position parameters using a first multi-segment PID algorithm, and calculating a temperature difference adjustment amount between an auxiliary control heating element and the main control heating element based on the offset of the interface curvature parameters using a second multi-segment PID algorithm, wherein the main control heating element and the auxiliary control heating element are used to control the temperature environment for crystal growth; adjusting the heating power of the main control heating element based on the temperature adjustment amount of the main control heating element, and adjusting the heating power of the auxiliary control heating element based on the temperature adjustment amount of the main control heating element and the temperature difference adjustment amount between the auxiliary control heating element and the main control heating element.

[0005] Optionally, in some embodiments of the present invention, the temperature adjustment of the main control heating element is calculated based on the offset of the interface position parameter using a first multi-segment PID algorithm, including the following steps: calculating the offset of the interface position parameter based on the ideal vertical position of the crystal growth solid-liquid interface in the crystal growth direction; and calculating the temperature adjustment of the main control heating element based on the offset of the interface position parameter.

[0006] Optionally, in some embodiments of the present invention, the temperature difference adjustment between the auxiliary heating element and the main heating element is calculated using a second multi-segment PID algorithm based on the offset of the interface curvature parameter, including the following steps: calculating the offset of the interface curvature parameter based on the interface curvature parameter of the ideal micro-convex interface of the crystal growth solid-liquid interface; and calculating the temperature difference adjustment between the auxiliary heating element and the main heating element based on the offset of the interface curvature parameter.

[0007] Optionally, in some embodiments of the present invention, the periods of the main heating element and the auxiliary heating element are adjusted independently, wherein the initial adjustment of the periods of the main heating element and the auxiliary heating element is an integer multiple of the minimum period obtained from the growth parameters of the crystal growth solid-liquid interface.

[0008] Optionally, in some embodiments of the present invention, the interface position parameter is obtained based on an image generated after X-ray identification of the solid-liquid interface of the crystal growth.

[0009] Optionally, in some embodiments of the present invention, the crystal is a fluoride crystal grown using a crucible lowering method, a heat exchange crucible lowering method, or a vertical gradient condensation method.

[0010] A second aspect of the present invention provides an automatic temperature control device for a crystal growth apparatus, comprising a processor, a memory, and a computer program stored in the memory and capable of running on the processor, wherein the computer program, when executed by the processor, implements the automatic temperature control method for a crystal growth apparatus as described in the first aspect of the present invention.

[0011] In a third aspect, the present invention provides a crystal growth system, comprising a crystal growth apparatus and an automatic temperature control device for the crystal growth apparatus as described in the second aspect of the present invention. The crystal growth apparatus comprises: an operating chamber for providing a high vacuum or high-purity atmosphere required for crystal growth; a temperature field with a downward opening, the temperature field being fixedly disposed within the operating chamber, and an insulating plate on the inner wall of the temperature field for dividing the temperature field into different intervals; a heating element comprising a main heating element and an auxiliary heating element disposed on the inner wall of the temperature field, the main heating element being disposed above the insulating plate and the auxiliary heating element being disposed below the insulating plate, the main heating element and the auxiliary heating element being used to adjust the temperature of different intervals of the temperature field; a crucible for holding materials required for crystal growth; a seed crystal rod for driving the crucible to move within different intervals of the temperature field; and an observation component for generating a crystal growth solid-liquid interface; wherein the automatic temperature control device for the crystal growth apparatus is electrically connected to the heating element and the observation component, and is used to automatically adjust the main heating element and the auxiliary heating element.

[0012] Optionally, in some embodiments of the present invention, the operating cavity includes a sealed furnace body, an X-ray window, and a bellows. The bottom of the furnace body is sealed to the bellows, and the X-ray window is sealed to the side wall of the furnace body to facilitate the passage of X-rays through the operating cavity. The observation assembly includes an X-ray source for emitting X-rays and a detector for receiving X-rays passing through the operating cavity. An X-ray source is disposed on one side of the operating cavity, and a detector is disposed on the other side. The positions of the X-ray source and the detector are matched with those of the X-ray window.

[0013] Optionally, in some embodiments of the present invention, the automatic temperature control device for the crystal growth apparatus is electrically connected to the seed crystal rod, and is used to control the solid-liquid interface of the crystal growth to be within the temperature field range corresponding to the insulation plate through the seed crystal rod.

[0014] The beneficial effects of this invention are as follows: The automatic temperature control method effectively solves the problem in existing technologies where crystal growth solid-liquid interface control cannot be achieved by adjusting the temperature control of the crystal growth device. Specifically, by utilizing the obtained interface position parameter z and interface curvature parameter δ to perform feedback correction on the temperature control of the main and auxiliary heating elements, automatic control of the crystal growth solid-liquid interface can be achieved. Furthermore, by selecting the interface position parameter z and interface curvature parameter δ as growth parameters characterizing the crystal growth state, the crystal growth state can be comprehensively reflected, simplifying the calculation process and achieving precise control of the main and auxiliary heating elements. The interface position is mainly determined by the temperature in the high-temperature range; therefore, the position parameter z is primarily controlled by adjusting the temperature control of the main heating element. Achieving a good interface curvature requires both that the interface be located within a temperature gradient range and that an appropriate temperature difference be maintained between the high-temperature and low-temperature ranges. Therefore, the interface curvature parameter δ is mainly controlled by adjusting the temperature difference between the auxiliary heating element and the main heating element. Since the temperature control of the main heating element and its adjustment amount are determined by the position parameter z, the temperature difference adjustment between the auxiliary and main heating elements can be controlled by adjusting the temperature control of the auxiliary heating element. By selecting the first multi-segment PID algorithm and the second multi-segment PID algorithm, precise adjustment of the temperature adjustment amounts of the main and auxiliary heating elements can be achieved. When multi-segment adjustment is required, it is only necessary to set the derivative and integral coefficients in the multi-segment PID algorithm to 0 to achieve multi-segment adjustment, which is convenient for different application scenarios. In addition to calculating the correction amount of the temperature control of the main heating element and the auxiliary heating element, the automatic temperature control method of the crystal growth device also calculates the adjustment period required before the next correction. The length of the adjustment period is determined by the absolute value of the offset Δz of the interface position parameter |Δz| and the absolute value of the offset Δδ of the curvature parameter |Δδ| during the previous feedback adjustment. This achieves the effect that the larger the deviation, the longer the adjustment period is required, which helps to avoid the adverse effects caused by excessive correction. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 is a schematic diagram of a growth furnace for a crystal growth apparatus provided by the present invention; Figure 2 is a flowchart of an automatic temperature control method for a crystal growth apparatus provided by the present invention.

[0017] Figure reference numerals: 101, temperature field; 102, main heating element; 103, crucible; 104, X-ray window; 105, solid-liquid interface for crystal growth; 106, insulation plate; 107, auxiliary heating element; 108, furnace body; 109, seed crystal rod; 110, bellows; 111, heating electrode of the main heating element; 112, heating electrode of the auxiliary heating element; 113, detector; 114, workstation; 115, control system; 116, temperature controller of the main heating element; 117, temperature controller of the auxiliary heating element; 118, power supply of the main heating element; 119, power supply of the auxiliary heating element. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention. In the present invention, unless otherwise stated, directional terms such as "up," "down," "left," "right," "front," and "back" generally refer to up, down, left, and right in the actual use or working state of the device, specifically the drawing directions in the accompanying drawings.

[0019] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments of the present invention. Furthermore, the descriptions of each embodiment in the following embodiments have their own emphasis; for parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0020] Please refer to Figure 1. This invention provides a crystal growth apparatus to facilitate understanding and implementation of the automatic temperature control method for a crystal growth apparatus mentioned in this invention. It is understood that Figure 1 provides an exemplary preferred embodiment for the crystal growth apparatus to facilitate understanding and implementation of the solution by those skilled in the art. Many other embodiments exist for the crystal growth apparatus, and this invention does not limit the crystal growth apparatus, as long as it can be used to implement the solution of this application. For example, in an alternative embodiment, Chinese Patent CN2023118372050 discloses a crystal growth observation device with a visual interface. This invention can implement the automatic temperature control method for a crystal growth apparatus based on the visual interface crystal growth observation device mentioned in that patent.

[0021] Referring to Figure 1, fluoride optical crystals can be grown using the crystal growth apparatus provided by this invention via a crucible lowering method. The growth apparatus includes an operating cavity, a temperature field 101, a heating element, a crucible 103, a seed crystal rod 109, and an observation element. The temperature field is located within the operating cavity and is a downward-opening cavity. The heating element is located within the cavity of the temperature field. Together, the temperature field and the heating element constitute the temperature environment required for crystal growth.

[0022] Specifically, the X-ray window 104, the furnace body 108, and the bellows 110 enclose and form an operating cavity. The X-ray window 104 is sealed and fixedly installed on the side wall of the furnace body 108 to facilitate the passage of X-rays through the operating cavity. The bellows 110 is located below the furnace body 108 to facilitate the partial placement of the seed crystal rod 109 within the operating cavity and its movement along the crystal growth direction within the operating cavity.

[0023] The crucible 103 is placed on the seed crystal rod 109 and surrounded by the temperature field 101. The crucible can be made of high-temperature resistant and corrosion-resistant materials such as graphite, glassy carbon, and molybdenum. A temperature insulation plate 106 is installed on the inner wall of the temperature field 101 to divide the temperature field into three temperature zones: an upper high-temperature zone, a lower low-temperature zone, and a temperature gradient region in the middle. The temperature field 101 and the temperature insulation plate 106 together construct the temperature distribution required for crystal growth. The temperature field 101 is made of high-temperature resistant materials with moderate thermal conductivity, such as graphite and molybdenum. The temperature insulation plate 106 is made of low-thermal-conductivity materials such as alumina, carbon felt, and porous graphite. It can be understood that in some specific application scenarios, the high-temperature zone, the low-temperature zone, and the temperature gradient region are interconnected. For example, in the crucible lowering method, the crucible can freely pass through the high-temperature zone to the low-temperature zone.

[0024] In the process of preparing crystals using the crucible descent method, the solid-liquid interface 105 of crystal growth is the boundary between the melt located at the top of the crucible and the crystal located at the bottom of the crucible. Ideally, it should be located in the temperature gradient region between the high-temperature range and the low-temperature range.

[0025] The heating element includes a main heating element 102 and an auxiliary heating element 107. The main heating element 102 and the auxiliary heating element 107 are located in the upper high-temperature zone and the lower low-temperature zone, respectively, responsible for providing heat to the two spaces and regulating the temperature within their respective zones. The main heating element 102 is connected to the main heating element power supply 118 via the main heating element heating electrode 111, and the auxiliary heating element 107 is connected to the auxiliary heating element power supply 119 via the auxiliary heating element heating electrode 112. The main heating element heating electrode 111 and the auxiliary heating element heating electrode 112 pass through the cavity of the furnace body 108 via a vacuum flange to ensure that the cavity of the furnace body 108 is in a highly sealed state, meeting the requirements of high vacuum or high-purity atmosphere for fluoride crystal growth.

[0026] The observation assembly includes a detector 113 and an X-ray source (not shown in the figure). An emitter is used to emit X-ray signals. The X-ray source is located on the opposite side of the detector 113 from the furnace body 108. The detector 113 receives the X-ray signal emitted by the X-ray source (not shown in the figure), which sequentially passes through the furnace cavity, temperature field, crucible, melt / crystal on one side of the X-ray source, and then through the crucible, temperature field, and furnace cavity on the other side of the detector. The Z-axis height of the detector and the X-ray source is the same as the height of the X-ray window 104. The X-ray window is preferably made of magnesium-aluminum alloy or titanium alloy, which combines the advantages of high strength, good corrosion resistance, and low density. This allows it to adapt to the high vacuum and highly corrosive environment required for fluoride crystal growth, while also reducing X-ray absorption and increasing the intensity of the X-ray signal reaching the detector after passing through the furnace cavity, temperature field, crucible, and melt / crystal.

[0027] After the detector 113 transmits the acquired projection signal to the workstation 114, the data processing software on the workstation 114 identifies the abrupt changes in X-ray signal caused by the density changes of the fluoride crystals and fluoride melt on both sides of the solid-liquid interface of the crystal growth, thus achieving two-dimensional imaging of the projection of the solid-liquid interface of the fluoride crystal growth in the observation direction. Furthermore, by rotating the crucible and the melt and crystals within it, X-ray projection imaging information is acquired during the rotation process, and the imaging data is reconstructed to achieve three-dimensional tomographic imaging of the solid-liquid interface of the fluoride crystal growth.

[0028] Therefore, by using a crystal growth apparatus, especially by observing the density difference between fluoride crystals in the crystalline and molten states using X-ray signals, and thus imaging the solid-liquid growth interface, it is possible to effectively observe the crystal state during the crystal growth process.

[0029] However, even if observation of the crystal growth process can be achieved through crystal growth equipment, it still cannot solve the crystal growth problem. In particular, the preparation of large-size fluoride optical crystals relies heavily on the experience of crystal growth personnel, and the growth control process is mostly based on continuous "trial and error" to gradually optimize parameters such as temperature control.

[0030] Therefore, the automatic temperature control method for a crystal growth apparatus provided in this application selects appropriate growth parameters and uses a multi-terminal automatic temperature control algorithm to adjust the temperature of the main heating element and the auxiliary heating element. Then, the main heating element and the auxiliary heating element are adjusted based on the temperature adjustment of the main heating element and the auxiliary heating element.

[0031] It is understandable that during the crystal growth process, the main heating element and the auxiliary heating element can adjust their respective power under the control of the control system to create an ideal temperature distribution in the crystal growth range.

[0032] Regarding the type of heating element and auxiliary heating element, this invention is not limited to this. They can have the same or different heating power, temperature control adjustment accuracy, etc., as long as they can meet the relevant requirements for crystal growth. This invention does not impose any restrictions on this.

[0033] Figure 2 shows a flowchart of an automatic temperature control method for crystal growth. The method selects appropriate growth parameters and uses a multi-terminal automatic temperature control algorithm to adjust the temperature of the main heating element and the auxiliary heating element. Then, the main heating element and the auxiliary heating element are adjusted based on the temperature adjustment of the main heating element and the auxiliary heating element.

[0034] S100: Obtain the growth parameters of the solid-liquid interface of the crystal growth, the growth parameters being used to characterize the growth state of the crystal.

[0035] S200: The first multi-segment automatic temperature control algorithm is used to calculate the temperature adjustment amount of the main control heating element based on the offset of the growth parameters, and the second multi-segment automatic temperature control algorithm is used to calculate the temperature difference adjustment amount between the auxiliary control heating element and the auxiliary control heating element based on the offset of the growth parameters.

[0036] S300: Adjust the main heating element based on the temperature adjustment amount of the main heating element, and adjust the auxiliary heating element based on the temperature adjustment amount of the main heating element and the temperature difference adjustment amount between the auxiliary heating element and the main heating element.

[0037] Therefore, the automatic temperature control method for crystal growth provided in this application can effectively achieve automatic temperature control during the crystal growth process. This avoids the problems in the prior art where the preparation of large-size fluoride optical crystals relies heavily on the experience of crystal growth personnel and mostly depends on continuous "trial and error" to gradually optimize parameters such as temperature control. This results in the inability to quantify operations during crystal growth, large operational errors, and a high failure rate.

[0038] It should be noted that the solid-liquid interface of crystal growth can be regarded as an isotherm with a temperature equal to the melting point of the crystal. Since the high-temperature range controlled by the main heating element plays a dominant role in the overall temperature of the crystal growth range, the temperature of the main heating element plays a major role in the vertical movement of the solid-liquid interface of crystal growth, i.e., the isotherm with a temperature equal to the melting point of the crystal. Therefore, the position of the solid-liquid interface can be adjusted by adjusting the temperature of the main heating element.

[0039] It should also be noted that the curvature (i.e., the degree of concavity and convexity) of the solid-liquid interface of crystal growth, which is the isotherm equivalent to the melting point of the crystal, depends on the axial and radial temperature gradients in the space where it is located; usually, the solid-liquid interface of crystal growth must be stabilized in the temperature gradient range and the temperature difference between the high-temperature range and the low-temperature range must be maintained at an appropriate value to obtain an ideal slightly convex solid-liquid interface for crystal growth. Therefore, on the premise of keeping the position of the solid-liquid interface optimized, the temperature difference between the high-temperature range and the low-temperature range can be constructed by adjusting the temperature controlled by the auxiliary control heating element, and then the curvature of the solid-liquid interface can be adjusted.

[0040] Please continue to refer to Figure 2. The following further elaborates on each step: S100: Obtain the growth parameters of the solid-liquid interface of crystal growth. The growth parameters are used to characterize the growth state of the crystal. The growth parameters include an interface position parameter and an interface curvature parameter. The interface position parameter is the position of the vertex of the solid-liquid interface of crystal growth in the crystal growth direction. The interface curvature parameter is the quotient of the height difference between the vertex and the edge of the solid-liquid interface of crystal growth in the crystal growth direction and the crystal diameter.

[0041] It can be understood that there are multiple choices when selecting the growth parameters for feedback on the crystal growth situation. The present invention preferably selects the interface position parameter z and the interface curvature parameter δ to reflect the crystal growth situation. The interface position parameter z is the position of the vertex of the solid-liquid interface of crystal growth in the crystal growth direction, generally the up-down (vertical) direction. The interface curvature parameter δ is the quotient of the height difference Δh between the vertex and the edge of the solid-liquid interface of crystal growth in the crystal growth direction and the crystal diameter D, that is, δ = Δh / D.

[0042] The purpose and advantage of such a setting are that, compared with other growth parameters, the combination of the interface position parameter z and the interface curvature parameter δ can better reflect the crystal growth state. For example, when δ > 0, the vertex of the solid-liquid interface of crystal growth is higher than the edge, and at this time, it corresponds to convex interface growth; when δ = 0, it corresponds to flat interface growth; when δ < 0, it corresponds to concave interface growth. Through the interface curvature parameter, the interface growth morphology can be better reflected, and then the morphology of the solid-liquid interface of crystal growth can be adjusted by adjusting the temperatures of the main control heating element and the auxiliary control heating element.

[0043] In some embodiments of the present invention, ideally, the solid-liquid interface of crystal growth should be located at the central position of the temperature gradient range, that is, ideally, the height of the vertex of the solid-liquid interface of crystal growth in the vertical direction is the same as the center of the heat insulation plate. Define this interface position parameter as the ideal value z0. z > z0 means that the vertex of the solid-liquid interface is higher than the central area position of the temperature gradient range, and it is necessary to appropriately increase the temperature controlled by the main control heating element; when z < z0, it means that the vertex of the solid-liquid interface is lower than the central area position of the temperature gradient range, and it is necessary to appropriately decrease the temperature controlled by the main control heating element.

[0044] In some embodiments of the present invention, the solid-liquid interface during crystal growth should maintain a slightly convex state, i.e., δ should remain positive and have a small absolute value. Preferably, the ideal value of δ can be defined as δ0 = 0.02. δ > δ0 means that the solid-liquid interface is too convex, and the temperature difference between the high-temperature and low-temperature ranges needs to be appropriately reduced; δ < δ0 means that the solid-liquid interface is too convex or even has a concave interface, and the temperature difference between the high-temperature and low-temperature ranges needs to be appropriately increased.

[0045] It should be noted that, in obtaining crystal growth parameters, as long as the interface position parameter z and interface curvature parameter δ can be obtained, there are no restrictions on the device used to obtain the parameters. Preferably, one embodiment of the present invention utilizes the density abrupt change at the solid-liquid interface of crystal growth (for example, for calcium fluoride crystals, the density difference between the solid and the melt is greater than 8%). Using the principle of X-ray projection imaging, the X-ray signal reaching the detector is detected after passing through the furnace cavity, temperature field, crucible, melt / crystal on one side of the X-ray source, and the crucible, temperature field, and furnace cavity on the other side of the detector. By identifying the abrupt change in X-ray signal caused by the density change of the fluoride crystal and fluoride melt on both sides of the solid-liquid interface of crystal growth, two-dimensional imaging of the projection of the solid-liquid interface of fluoride crystal growth in the observation direction is achieved. Based on this, the obtained X-ray projection imaging information is processed to identify the position of the vertex of the solid-liquid interface of crystal growth, the height difference Δh between the vertex and the edge of the solid-liquid interface in the crystal growth direction, and the crystal diameter D. This is relatively simple and fast, and does not require a lot of computational programs and hardware support. Naturally, it is easier to obtain the interface position parameter z and interface curvature parameter δ.

[0046] It should be noted that, in some embodiments of the present invention, the data acquisition, analysis, and processing of the interface position parameter z and interface curvature parameter δ in stage S100 are all completed in the workstation to reduce the computational burden on the control system. The workstation then sends the position parameter z and interface curvature parameter δ data to the control system. That is, the control system directly obtains the crystal growth solid-liquid interface growth parameters processed by the workstation and completes other steps accordingly. Of course, the control system can also obtain the interface position parameter z and interface curvature parameter δ of S100 and perform data acquisition, analysis, and processing; this application does not limit this approach.

[0047] S200: The temperature adjustment amount of the main control heating element is calculated based on the offset of the interface position parameter using a first multi-segment PID algorithm, and the temperature difference adjustment amount between the auxiliary control heating element and the main control heating element is calculated based on the offset of the interface curvature parameter using a second multi-segment PID algorithm, wherein the main control heating element and the auxiliary control heating element are used to control the temperature environment for crystal growth.

[0048] After obtaining the interface position parameter z and the interface curvature parameter δ, the control logic and concept for the main control heating element and the auxiliary control heating element can be realized based on the interface position parameter z and the interface curvature parameter δ as follows: (1) Based on the interface position parameter z, change the temperature control temperature of the main control heating element located in the high-temperature range.

[0049] When z > z0, the position of the crystal growth solid-liquid interface is relatively high, that is, the high-temperature range in the upper part deviates, which means that the overall temperature of the crystal growth space is relatively low at this time; at this time, increase the temperature control temperature of the main control heating element, and the isotherm of the crystal growth space moves down as a whole, and the crystal growth solid-liquid interface moves down. When z < z0, the position of the crystal growth solid-liquid interface is relatively low, that is, the low-temperature range in the lower part deviates, which means that the overall temperature of the crystal growth space is relatively high at this time; at this time, reduce the temperature control temperature of the main control heating element, and the isotherm of the crystal growth space moves up as a whole, and the crystal growth solid-liquid interface moves up.

[0050] (2) Based on the interface curvature parameter δ, change the temperature difference between the auxiliary control heating element located in the low-temperature range and the main control heating element located in the high-temperature range.

[0051] Since the temperature control temperature of the main control heating element has been adjusted based on the position parameter z, the temperature control temperature of the auxiliary control heating element can be adjusted on this basis to change the temperature difference between the auxiliary control heating element and the main control heating element located in the high-temperature range. Specifically, when δ > δ0, the convexity degree of the crystal growth solid-liquid interface is greater than the critical value δ0, which means that the temperature difference between the high-temperature range and the low-temperature range is too large at this time; at this time, by changing the temperature control temperature of the auxiliary control heating element, reduce the temperature difference between the high-temperature range and the low-temperature range, and reduce the convexity degree of the crystal growth solid-liquid interface. When δ < δ0, the convexity degree of the crystal growth solid-liquid interface is too small or even there is a concave interface, which means that the temperature difference between the high-temperature range and the low-temperature range is too small at this time; at this time, change the temperature control temperature of the auxiliary control heating element located in the low-temperature range, increase the temperature difference between the high-temperature range and the low-temperature range, and realize the transformation of the crystal growth solid-liquid interface from a concave interface to a flat interface and even a convex interface.

[0052] Specifically, after obtaining the interface position parameter z and the interface curvature parameter δ, in order to more accurately control the main control heating element and the auxiliary control heating element, the present invention realizes the precise control of the temperature of the crystal growth environment by introducing the first multi-segment automatic temperature control algorithm and the second multi-segment automatic temperature control algorithm. That is, use the first multi-segment automatic temperature control algorithm to calculate the temperature adjustment amount of the main control heating element based on the offset of the growth parameter, and use the second multi-segment automatic temperature control algorithm to calculate the temperature difference adjustment amount between the auxiliary control heating element and the main control heating element based on the offset of the growth parameter.

[0053] Specifically, in some embodiments of the present invention, the temperature adjustment amount of the main heating element is calculated based on the offset of the growth parameters using a first multi-segment automatic temperature control algorithm, including the following steps: First, calculate the offset Δz of the interface position parameter, Δz = z - z0, where z0 is the ideal perpendicular position of the crystal growth direction at the solid-liquid interface of the crystal growth; Second, calculate the temperature adjustment amount ΔT of the main heating element according to the numerical range of the absolute value |Δz| of the offset Δz of the interface position parameter. z .

[0054] Optionally, in some embodiments of the present invention, the temperature adjustment amount ΔT of the main control heating element is calculated based on the absolute value |Δz| of the offset of the interface position parameter. z The calculation is performed using the first multi-segment PID algorithm, and the calculation method is as follows: Wherein, coefficient K pzx K izx K dzx (x = 1, 2, 3, ...) is related to the absolute value of the offset Δz, |Δz|.

[0055] Preferably, in some embodiments of the present invention, the coefficient can be set as: K pz1 =50, K iz1 =100, K dz1 =1 (0≤|Δz|<5mm) K pz2 =25, K iz2 =200, K dz2 =1 (5mm≤|Δz|<10mm) K pz3 =25, K iz3 =250, K dz3 =1 (10mm≤|Δz|<20mm) K pz4 =50, K iz4 =250, K dz4 =1 (20mm≤|Δz|) Therefore, by employing a multi-segment PID algorithm, when the absolute offset of the interface position parameter |Δz| is small, a set of PID parameters K with a smaller correction strength is used. pz1 K iz1 K dz1 As |Δz| increases, the correction strength of the corresponding PID parameter increases accordingly.

[0056] Optionally, in some embodiments of the present invention, the temperature difference adjustment between the auxiliary heating element and the main heating element is calculated based on the offset of the growth parameters using a second multi-segment automatic temperature control algorithm, including the following steps: First, calculate the offset Δδ of the interface curvature parameter, Δδ = δ - δ0, where δ0 is the interface curvature parameter of the ideal micro-convex interface; Second, calculate the temperature difference adjustment ΔT between the auxiliary heating element and the main heating element based on the numerical range of the absolute value |Δδ| of the offset Δδ of the interface curvature parameter. δ .

[0057] Optionally, in some embodiments of the present invention, the temperature difference adjustment amount ΔT between the auxiliary heating element and the main heating element is calculated based on the absolute value |Δδ| of the offset of the interface curvature parameter. δ The calculation is performed using the second multi-segment PID algorithm, and the calculation method is as follows: Wherein, coefficient K pδx K iδx K dδx (x = 1, 2, 3 ...) is related to the absolute value of the offset Δδ, |Δδ|.

[0058] Preferably, in some embodiments of the present invention, the coefficient can be set as: K pδ1 =25, K iδ1 =100, K dδ1 =1 (0≤|Δδ|<0.02) K pδ2 =15, K iδ2 =150, K dδ2 =0 (0.02≤|Δδ|<0.05) K pδ3 =15, K iδ3 =200, K dδ3 =0 (0.05≤|Δδ|<0.08) K pδ4 =25, K iδ4 =200, K dδ4 =0 (0.08≤|Δδ|) Therefore, by employing a multi-segment PID algorithm, when the absolute offset of the interface position parameter |Δδ| is small, a set of PID parameters K with a smaller correction strength is used. pδ1 K iδ1 K dδ1 As |Δδ| increases, the correction strength of the corresponding PID parameter increases accordingly.

[0059] It should be noted that, in some embodiments of the present invention, the temperature adjustment amount of the main control heating element is ΔT. z The temperature adjustment amount of the auxiliary heating element is ΔT. z +ΔT δ .

[0060] Optionally, in some embodiments of the present invention, the temperature adjustment amount ΔT of the main heating element is used as the basis. z Adjust the temperature T of the main heating element z Specifically, by adjusting the power of the main control heating element, the monitored temperature T of the main control heating element is adjusted. z Adjust to the target temperature control temperature T z +ΔT z Based on the temperature adjustment amount ΔT of the auxiliary heating element. z +ΔT δ Adjust the temperature T of the auxiliary heating element δ And by adjusting the power of the auxiliary heating element, the monitored temperature T of the auxiliary heating element is controlled. δ Adjust to the target temperature control temperature T δ +ΔT z +ΔT δ .

[0061] The present invention provides an automatic temperature control method for a crystal growth apparatus, which further includes: during the crystal growth process, after activating the automatic temperature control function of the crystal growth apparatus, initially controlling the temperature T of the main heating element. z Adjustment and temperature control of auxiliary heating element T δ The adjustment period required is t0.

[0062] t0 is an integer multiple of the minimum period for obtaining growth parameters at the solid-liquid interface of crystal growth.

[0063] In some embodiments of the present invention, the interface position parameter is obtained through image post-processing of the crystal growth solid-liquid interface, wherein the image of the crystal growth solid-liquid interface is formed based on X-ray identification of density abrupt changes on both sides of the crystal growth solid-liquid interface. When the interface position parameter z and the interface curvature parameter δ are obtained through X-ray identification of the crystal growth solid-liquid interface formed by signal abrupt changes due to density abrupt changes on both sides of the crystal growth solid-liquid interface, t0 is equal to the completion period of the crystal growth solid-liquid interface imaging process.

[0064] After this, the temperature T of the main heating element is controlled. z Adjustment and temperature control of auxiliary heating element T δ The adjustments will be made independently.

[0065] Specifically, the current temperature T of the main heating element is adjusted. z During the process, the absolute value of the offset Δz of the interface position parameter, |Δz|, is used as the input parameter to calculate the temperature T of the main heating element for the next operation. z The adjustment period t z .

[0066] Optionally, in some embodiments of the present invention, the period t is updated based on the currently described interface position parameters. z The update standard is obtained through the first cycle algorithm, which is as follows:

[0067] Specifically, the current temperature T of the main heating element is adjusted. δ During the process, the absolute value of the offset Δδ of the interface position parameter, |Δδ|, is used as the input parameter to calculate the temperature T of the main heating element for the next operation. δ The adjustment period t δ .

[0068] Optionally, in some embodiments of the present invention, the period t is updated based on the currently described interface position parameters. δ The update standard is obtained through a second-cycle algorithm, which is as follows:

[0069] It should be noted that, in some embodiments of the present invention, the calculation of the temperature adjustment amount and temperature difference adjustment amount in stage S200 is completed in the processor of the control system. Subsequently, the control system feeds back the target temperature values ​​of the main heating element and the auxiliary heating element to the main heating element temperature controller and the auxiliary heating element temperature controller. At the same time, the control system will determine the next temperature T of the main heating element. z The adjustment period t z The next temperature T of the main heating element will be controlled. δ The adjustment period t δ Feedback is sent to the workstation.

[0070] S300: Adjust the heating power of the main heating element based on the temperature adjustment amount of the main heating element, and adjust the heating power of the auxiliary heating element based on the temperature adjustment amount of the main heating element and the temperature difference adjustment amount between the auxiliary heating element and the main heating element.

[0071] Specifically, the temperature control setting of the main heating element is adjusted based on the temperature adjustment amount of the main heating element, and the monitoring temperature of the main heating element is adjusted to its controlled temperature by adjusting the power of the main heating element. The temperature control setting of the auxiliary heating element is adjusted based on the temperature adjustment amount of the main heating element and the temperature difference adjustment amount between the auxiliary heating element and the main heating element, and the monitoring temperature of the auxiliary heating element is adjusted to its controlled temperature by adjusting the power of the auxiliary heating element.

[0072] Specifically, in one implementation, the control system sends the target temperature value of the main heating element to the main heating element temperature controller. After receiving the target temperature value, the main heating element temperature controller adjusts the power output of the main heating element according to the measured temperature fed back by the thermocouple of the main heating element temperature monitoring system, and adjusts the actual temperature of the main heating element to the set value based on the built-in PID algorithm of the main heating element temperature controller.

[0073] Similarly, the control system sends the target temperature value of the auxiliary heating element to the main heating element temperature controller. After receiving the target temperature value of the main heating element, the auxiliary heating element temperature controller adjusts the power output of the auxiliary heating element according to the measured temperature feedback from the temperature monitoring thermocouple of the auxiliary heating element, and adjusts the actual temperature of the auxiliary heating element to the set value according to the built-in PID algorithm of the auxiliary heating element temperature controller.

[0074] Furthermore, the control system sends the next temperature T for controlling the main heating element. z The adjustment period t z and the next temperature T of the auxiliary heating element. δ The adjustment period t δ The workstation receives the temperature T for the next temperature control of the main heating element. z The adjustment period t z and the next temperature T of the main heating element. δ The adjustment period t δ Afterwards, in t z Then, the interface position parameters are read again, and the adjustment of the main control heating element temperature is fed back; at t δ Then, the curvature parameters of the interface are read here, and the temperature of the auxiliary heating element is adjusted accordingly.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0076] Please refer to Figure 1. After applying the automatic temperature control method for crystal growth apparatus provided in this application in the crystal growth apparatus shown in Figure 1, the control system first obtains the growth parameters of the solid-liquid interface of crystal growth through the detector 113 and the working device, preferably the interface position parameter z and the interface curvature parameter δ.

[0077] Specifically, after workstation 114 obtains the interface position parameter z and interface curvature parameter δ through processing, and calculates the temperature adjustment amount of the main control heating element and the auxiliary control heating element, it sends the target temperature control temperature of the main control heating element and the target temperature control temperature of the auxiliary control heating element to control system 115. Control system 115 is a control system integrating components such as processor, memory, and communication module. The processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., which will not be elaborated further.

[0078] Subsequently, the control system 115 uses a first multi-segment automatic temperature control algorithm to calculate the temperature adjustment of the main control heating element based on the offset of the growth parameters, and uses a second multi-segment automatic temperature control algorithm to calculate the temperature difference adjustment between the auxiliary control heating element and the main control heating element based on the offset of the growth parameters.

[0079] Subsequently, the control system 115 adjusts the main heating element based on the temperature adjustment amount of the main heating element 102, and adjusts the auxiliary heating element based on the temperature adjustment amount of the main heating element 102 and the temperature difference adjustment amount between the auxiliary heating element 107 and the main heating element. Specifically, the control system 115 can convert the output signal generated by the software of the workstation 114 into a control signal that the temperature controller can recognize, thereby driving the main heating element temperature controller 116 and the auxiliary heating element temperature controller 117 to set the temperature. The main heating element temperature controller 116 adjusts the power output of the main heating element 102 according to the temperature setting given by the control system 115 and the measured temperature fed back by the temperature monitoring thermocouple (not marked in the figure) of the main heating element 102, thereby adjusting the actual temperature of the main heating element 102 to the set value. The auxiliary heating element temperature controller 117 adjusts the power output of the auxiliary heating element 107 according to the temperature setting given by the control system 115 and the actual temperature fed back by the temperature monitoring thermocouple (not marked in the figure) of the auxiliary heating element 107, thereby adjusting the actual temperature of the auxiliary heating element to the set value.

[0080] It should be noted that the controller circuits and devices used to control the heating temperatures of the main and auxiliary heating elements include one or more sub-controller circuits and devices. These are at least used to control the heating temperatures of the main and auxiliary heating elements, thereby controlling crystal growth. Of course, they can also be connected to other devices to achieve more control functions, such as controlling the cooling rate of the crystal. The processor, memory, and communication module in the control system are coupled together, allowing the control system to be controlled by the processor to execute corresponding controls. It should be pointed out that although the detailed structure of the control system is not shown in the figure, any two or more devices in the control system—the processor, memory, communication module, and the growth furnace used for crystal growth—can be electrically or mechanically coupled together as needed.

[0081] It should also be noted that the crystal growth method mainly utilizes the melt method, but the present invention is not limited to this in the specific implementation of the melt method. In one specific embodiment provided by the present invention, a crucible lowering method is used to grow fluoride optical crystals; of course, a heat exchange crucible lowering method or a vertical gradient condensation method can also be used to grow fluoride optical crystals.

[0082] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

Claims

1. An automatic temperature control method for a crystal growth apparatus, the method comprising: obtaining growth parameters of a solid-liquid interface of a crystal growth, the growth parameters being used to characterize a growth state of the crystal, the growth parameters comprising an interface position parameter and an interface curvature parameter, the interface position parameter being a position of a vertex of the solid-liquid interface of the crystal growth in a crystal growth direction, the interface curvature parameter being a quotient of a height difference between the vertex and an edge of the solid-liquid interface of the crystal growth in the crystal growth direction and a diameter of the crystal; calculating a temperature adjustment amount of a main heating body based on a deviation of the interface position parameter using a first multi-section PID algorithm and calculating a temperature difference adjustment amount of a secondary heating body and the main heating body based on a deviation of the interface curvature parameter using a second multi-section PID algorithm, wherein the main heating body and the secondary heating body are used to control a temperature environment of the crystal growth; adjusting a heating power of the main heating body based on the temperature adjustment amount of the main heating body and adjusting a heating power of the secondary heating body based on the temperature adjustment amount of the main heating body and the temperature difference adjustment amount of the secondary heating body and the main heating body.

2. The automatic temperature control method for the crystal growth apparatus according to claim 1, the method comprising: calculating the temperature adjustment amount of the main heating body based on the deviation of the interface position parameter using the first multi-section PID algorithm, comprising: calculating the deviation of the interface position parameter based on an ideal vertical position of the solid-liquid interface of the crystal growth in the crystal growth direction; and calculating the temperature adjustment amount of the main heating body based on the deviation of the interface position parameter.

3. The automatic temperature control method for the crystal growth apparatus according to claim 2, the method comprising: calculating the temperature difference adjustment amount of the secondary heating body and the main heating body based on the deviation of the interface curvature parameter using the second multi-section PID algorithm, comprising: calculating the deviation of the interface curvature parameter based on an interface curvature parameter of an ideal micro-convex interface of the solid-liquid interface of the crystal growth; and calculating the temperature difference adjustment amount of the secondary heating body and the main heating body based on the deviation of the interface curvature parameter.

4. The automatic temperature control method for the crystal growth apparatus according to claim 3, wherein: the periods of adjusting the main heating body and the secondary heating body are independent of each other, and wherein: a first period of adjusting the main heating body and the secondary heating body is an integer multiple of a minimum period of obtaining the growth parameters of the solid-liquid interface of the crystal growth.

5. The automatic temperature control method for the crystal growth apparatus according to any one of claims 1-4, wherein: the interface position parameter is obtained based on an image generated after the solid-liquid interface of the crystal growth is identified by X-ray.

6. The automatic temperature control method for the crystal growth apparatus according to any one of claims 1-5, wherein: the crystal is a fluoride crystal grown by a Bridgman method, a heat exchange Bridgman method or a vertical gradient freeze method.

7. An automatic temperature control device for a crystal growth apparatus, the device comprising: a processor, a memory, and a computer program stored on the memory and executable on the processor, the computer program being executed by the processor to implement the automatic temperature control method for the crystal growth apparatus according to any one of claims 1-6.

8. A crystal growth system, the system comprising: a crystal growth apparatus; and an automatic temperature control device for the crystal growth apparatus according to claim 7. ​ ​ ​ ​ ​ ​ ​ ​ 5. The method for automatically controlling temperature for a crystal growing apparatus according to any one of claims 1 to 4, wherein ​ 6. The method for automatically controlling temperature for a crystal growing apparatus according to any one of claims 1 to 4, wherein ​ ​ ​ ​ The crystal growth device comprises a crystal growth device and an automatic temperature control device for the crystal growth device as claimed in claim 7, wherein the crystal growth device comprises: an operation cavity for providing a high vacuum or a high-purity gas atmosphere required for crystal growth; a temperature field with a downward opening, which is fixedly arranged in the operation cavity, and a temperature partition plate arranged on the inner wall of the temperature field for partitioning the temperature field into different zones; a heating assembly comprising a main heating body and an auxiliary heating body arranged on the inner wall of the temperature field, the main heating body being arranged above the temperature partition plate and the auxiliary heating body being arranged below the temperature partition plate, the main heating body and the auxiliary heating body being used for adjusting the temperature of different zones of the temperature field; a crucible for placing materials required for crystal growth; a seed rod for driving the crucible to move in different zones of the temperature field; an observation assembly for generating a crystal growth solid-liquid interface; wherein the automatic temperature control device for the crystal growth device is electrically connected with the heating assembly and the observation assembly, and is used for automatically adjusting the main heating body and the auxiliary heating body.

9. The crystal growth system according to claim 8, wherein the operation cavity comprises a furnace body, an X-ray window and a bellows, the bottom of the furnace body is sealingly connected with the bellows, and the X-ray window is sealingly connected with the side wall of the furnace body for facilitating the passage of X-rays from the operation cavity, wherein the observation assembly comprises an X-ray source for emitting X-rays and a detector for receiving X-rays passing through the operation cavity, one side of the operation cavity is provided with the X-ray source, and the other side is provided with the detector, and the X-ray source and the detector are matched with the position of the X-ray window.

10. The crystal growth system according to claim 8, wherein the automatic temperature control device for the crystal growth device is electrically connected with the seed rod, and is used for controlling the crystal growth solid-liquid interface to be in the temperature field zone corresponding to the temperature partition plate through the seed rod.

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