Closed-loop regulation and control method for crystal growth state through descent method

Abstract

The invention discloses a descent method crystal growth state closed-loop regulation and control method, which comprises the following steps of: acquiring an electric signal of crystal state change in a crucible by utilizing the difference of penetration characteristics of X-rays to substances with different densities, and then analyzing the signal and adjusting the power of a heater in a growth area in real time based on a PID (Proportion Integration Differentiation) control algorithm so as to regulate the crystal growth state. The crystallization rate and the crucible descending speed are ensured to be consistent, and closed-loop regulation and control of the crystal growth state are finally realized. The closed-loop regulation and control method adopted by the invention can directly overcome the problems of temperature field drift, equipment loss, environmental interference and the like, not only realizes the whole-course automatic control of the crystal growth process, but also remarkably improves the quality consistency and yield of different batches of crystals, and has the characteristics of good repeatability and low risk.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal growth, and in particular to a closed-loop control method for crystal growth state using a descending method. Background Art

[0002] In the traditional crystal growth process using the descent method, the raw crystal material and the growing crystal are encapsulated together in an unobservable crucible due to the insulation structure and the heater. This results in the entire crystal growth process, from seeding to completion, being in a completely unobservable "black box" state. This closed nature prevents direct access to key state information such as the position of the solid-liquid interface, crystal growth rate, and defect formation. Process control relies heavily on temperature data indirectly measured by temperature sensors placed outside the crucible. However, this indirect temperature measurement method has inherent hysteresis and errors caused by other structural instabilities, forcing process personnel to establish an empirical correspondence between crystal position and external temperature through a large number of repeated experiments, and accordingly formulate a set of process control parameters for production.

[0003] The fundamental challenge facing the above control method is that it cannot effectively deal with the variables and disturbances inherent in the production process. For example, there are differences in the performance of insulation materials and heater efficiency between different batches. As the equipment is used, the thermal insulation effect of the temperature field will decline due to material aging, and the performance of the heater will also decline due to wear and tear. In addition, the influence of ambient temperature fluctuations will cause the actual temperature field characteristics in the furnace to deviate significantly from the baseline state set in the initial test. As a result, the fixed process parameters set based on the previous empirical model are difficult to stably reproduce the same temperature environment and crystal growth conditions in subsequent mass production.

[0004] Therefore, in actual production, process personnel are forced to rely heavily on their personal experience to subjectively adjust process parameters in an attempt to compensate for temperature field characteristic drift. This experience-based adjustment method, lacking real-time objective process data feedback, not only suffers from poor repeatability and high risk, but also makes it difficult to ensure consistent crystal quality between batches, ultimately posing a significant obstacle to achieving stable and efficient mass production. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for controlling the crystal growth state by the descent method, so as to realize real-time direct monitoring and closed-loop dynamic control of the crystal growth state, and solve the technical problems that the prior art cannot directly monitor the growth state of the crystal, needs to rely on empirical control, has poor repeatability, and is difficult to ensure the consistency of crystal quality in mass production.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: A closed-loop control method for crystal growth state by a descent method comprises the following steps: (1) An X-ray emitter and an X-ray receiver are symmetrically mounted on two outer sides of a crystal growth device, and the positions of the crucible inside the crucible in the initial state and the positions corresponding to the boundaries between the seed crystal and the crystal raw material inside the crucible are marked on the two outer sides of the crystal growth device; the seed crystal and the crystal raw material are sequentially filled into the crucible from bottom to top; (2) The crucible is heated until the temperature reaches 90-99% of the melting point of the crystal raw material, and then the X-ray emitter and X-ray receiver are synchronously moved along the crucible axis at the same speed and direction to scan the entire crucible area; during the movement, the detection signal of the X-ray receiver is continuously read, and the obtained detection signal reflects the basic signal value at different positions of the crucible; then, the signal difference caused by the difference in the crucible structure is eliminated through software compensation, so that the basic signal value at different positions of the crucible is consistent with the basic signal value of the equal diameter section; (3) moving the X-ray emitter and the X-ray receiver to a position facing the bottom of the crystal raw material, continuing to heat the crucible, and processing the detection signal of the X-ray receiver in real time by the software compensation method described in step (2); when the value of the compensated detection signal suddenly changes compared with the value of the basic signal of the equal diameter section and exceeds a preset first threshold value, it is determined that the crystal raw material in the crucible is close to being fully melted; when the fluctuation of the compensated detection signal is lower than a preset second threshold value, it is determined that the crystal raw material has been completely melted, and the compensated detection signal at this time is recorded and recorded as signal one; (4) When all the crystal raw materials are melted, the heating power is kept constant, and the X-ray emitter and the X-ray receiver are moved downward by a distance equal to the diameter of the seed crystal, so that the X-ray emitter and the X-ray receiver are facing the upper end of the seed crystal. The X-ray detection signal of the upper end of the seed crystal is processed in real time by the software compensation method described in step (2), and the obtained signal is recorded as signal 2. When the difference between signal 2 and signal 1 is within the preset third threshold range, it is determined that the seed crystal has begun to melt. At this time, a certain amount of heating power should be reduced to maintain the state of the seed crystal unchanged and prevent the seed crystal from further melting, so as to realize the seeding process; then, the heating power is kept constant until the state of the crystal raw materials reaches a stable state, and the compensated detection signal at this time is recorded as signal 3; (5) Keeping the positions of the X-ray emitter and the X-ray receiver unchanged, the crucible is lowered at the set speed, and the signal values ​​at different positions of the crucible are continuously monitored by the X-ray emitter and the X-ray receiver, and the signal values ​​are processed in real time by the software compensation method described in step (2), and the processed signal values ​​are recorded as signal four, and the difference between signal four and signal three is calculated; a PID control algorithm is used to adjust the heater power of the growth zone in real time based on the difference, to ensure that the difference fluctuates within the set range, so that the crystallization rate is consistent with the crucible descent speed; at the same time, the heater power of the melting zone and the annealing zone is synchronously adjusted according to the preset process parameters, and finally a closed-loop control of the entire crystal growth process is achieved.

[0007] Furthermore, the X-ray output end of the X-ray emitter is provided with a collimating hole for generating a collimated X-ray beam with a reduced beam diameter.

[0008] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention proposes a closed-loop control method for crystal growth by the descent method. This method uses the difference in the penetration characteristics of X-rays for materials of different densities to obtain electrical signals indicating changes in the crystal state in the crucible. These signals are then analyzed and, based on a PID control algorithm, the heater power in the growth zone is adjusted in real time to ensure that the crystallization rate is consistent with the crucible descent speed, ultimately achieving closed-loop control of the crystal growth state. The closed-loop control method adopted by the present invention can directly overcome problems such as temperature field drift, equipment loss, and environmental interference. It not only achieves full automatic control of the crystal growth process, but also significantly improves the quality consistency and yield rate of different batches of crystals, with the characteristics of good repeatability and low risk.

[0009] 2. This invention utilizes a reflective structure within the X-ray emitter (to focus scattered radiation) in conjunction with a collimating aperture at the emitter's exit (to physically filter stray radiation), synergistically creating a directional X-ray stream with high energy density and a small beam diameter. The high energy density effectively enhances X-ray penetration, while the small beam diameter enables precise capture of millimeter-level positional variations at the solid-liquid interface, improving spatial resolution. Furthermore, the collimating aperture eliminates ambient scattering noise, enhancing signal purity and fundamentally guaranteeing the authenticity of growth status feedback. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural schematic diagram of the crystal growth device of the present invention.

[0011] In the figure, there is a crystal growth device 1, a heat-insulating layer 2, a heater 3, a crucible 4, a seed crystal 5, a crystal raw material 6, an X-ray emitter 7, and an X-ray receiver 8. DETAILED DESCRIPTION

[0012] The specific implementation methods of the present invention are further described in detail below with reference to specific examples.

[0013] X-rays have the ability to penetrate most materials, and their penetration varies significantly across materials of varying densities. Based on this characteristic, the present invention symmetrically installs X-ray emitters and receivers on either side of the crystal growth apparatus. The electrical signals generated by the X-ray receivers characterize the changes in the crystal material within the crucible, guiding the adjustment of process parameters and ultimately achieving real-time, direct monitoring and closed-loop dynamic control of the crystal growth state.

[0014] Based on the above research: The present invention provides a closed-loop control method for crystal growth state by descending method, the device used is as follows Figure 1As shown, the crystal growth device 1 includes an insulation layer 2, a heater 3, a crucible 4 installed in the crystal growth device 1, the crucible 4 is filled with seed crystals 5 and crystal raw materials 6 from bottom to top, and X-ray emitters 7 and X-ray receivers 8 are symmetrically installed on both outer sides of the crystal growth device 1, and the X-ray emitters 7 and X-ray receivers 8 can move up and down in the vertical direction.

[0015] The following steps are involved: (1) An X-ray emitter and an X-ray receiver are symmetrically mounted on two outer sides of a crystal growth device, and the positions of the crucible inside the crucible in the initial state and the positions corresponding to the boundaries between the seed crystal and the crystal raw material inside the crucible are marked on the two outer sides of the crystal growth device; the seed crystal and the crystal raw material are sequentially filled into the crucible from bottom to top; (2) The crucible is heated until the temperature reaches 90-99% of the melting point of the crystal raw material, and then the X-ray emitter and X-ray receiver are synchronously moved along the crucible axis at the same speed and direction to scan the entire crucible area; during the movement, the detection signal of the X-ray receiver is continuously read, and the obtained detection signal reflects the basic signal value at different positions of the crucible; then, the signal difference caused by the difference in the crucible structure is eliminated through software compensation, so that the basic signal value at different positions of the crucible is consistent with the basic signal value of the equal diameter section; (3) moving the X-ray emitter and the X-ray receiver to a position facing the bottom of the crystal raw material, continuing to heat the crucible, and processing the detection signal of the X-ray receiver in real time by the software compensation method described in step (2); when the value of the compensated detection signal suddenly changes compared with the value of the basic signal of the equal diameter section and exceeds a preset first threshold value, it is determined that the crystal raw material in the crucible is close to being fully melted; when the fluctuation of the compensated detection signal is lower than a preset second threshold value, it is determined that the crystal raw material has been completely melted, and the compensated detection signal at this time is recorded and recorded as signal one; (4) When all the crystal raw materials are melted, the heating power is kept constant, and the X-ray emitter and the X-ray receiver are moved downward by a distance equal to the diameter of the seed crystal, so that the X-ray emitter and the X-ray receiver are facing the upper end of the seed crystal. The X-ray detection signal of the upper end of the seed crystal is processed in real time by the software compensation method described in step (2), and the obtained signal is recorded as signal 2. When the difference between signal 2 and signal 1 is within the preset third threshold range, it is determined that the seed crystal has begun to melt. At this time, a certain amount of heating power should be reduced to maintain the state of the seed crystal unchanged and prevent the seed crystal from further melting, so as to realize the seeding process; then, the heating power is kept constant until the state of the crystal raw materials reaches a stable state, and the compensated detection signal at this time is recorded as signal 3; (5) Keeping the positions of the X-ray emitter and the X-ray receiver unchanged, the crucible is lowered at the set speed, and the signal values ​​at different positions of the crucible are continuously monitored by the X-ray emitter and the X-ray receiver, and the signal values ​​are processed in real time by the software compensation method described in step (2), and the processed signal values ​​are recorded as signal four, and the difference between signal four and signal three is calculated; a PID control algorithm is used to adjust the heater power of the growth zone in real time based on the difference, to ensure that the difference fluctuates within the set range, so that the crystallization rate is consistent with the crucible descent speed; at the same time, the heater power of the melting zone and the annealing zone is synchronously adjusted according to the preset process parameters, and finally a closed-loop control of the entire crystal growth process is achieved.

[0016] In specific implementations, the X-ray emitter is equipped with an X-ray reflection structure to increase the energy density of the emitted X-rays. A collimating aperture is provided at the X-ray output end of the X-ray emitter to produce a collimated X-ray beam with a reduced beam diameter. This reduces interference and produces an X-ray stream with high energy density and a small beam diameter. High energy density effectively improves the penetration of X-rays, while a small beam diameter enables precise capture of millimeter-level positional changes at the solid-liquid interface, improving spatial resolution. The collimating aperture also eliminates ambient scattering noise, improving signal purity and fundamentally ensuring the authenticity of growth status feedback. The reflective structure is prior art and will not be described in detail.

[0017] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A closed-loop control method for crystal growth state by a descending method, characterized in that: The following steps are involved: (1) An X-ray emitter and an X-ray receiver are symmetrically mounted on two outer sides of a crystal growth device, and the positions of the crucible inside the crucible in the initial state and the positions corresponding to the boundaries between the seed crystal and the crystal raw material inside the crucible are marked on the two outer sides of the crystal growth device; the seed crystal and the crystal raw material are sequentially filled into the crucible from bottom to top; (2) The crucible is heated until the temperature reaches 90-99% of the melting point of the crystal raw material, and then the X-ray emitter and X-ray receiver are moved synchronously along the crucible axis at the same speed and direction to scan the entire crucible area; During the movement, the detection signal of the X-ray receiver is continuously read. The obtained detection signal reflects the basic signal value at different positions of the crucible. Then, through software compensation, the signal difference caused by the difference in the crucible structure is eliminated, so that the basic signal value at different positions of the crucible is consistent with the basic signal value of the equal diameter section. (3) moving the X-ray emitter and the X-ray receiver to a position facing the bottom of the crystal raw material, continuing to heat the crucible, and processing the detection signal of the X-ray receiver in real time by the software compensation method described in step (2); when the value of the compensated detection signal suddenly changes compared with the value of the basic signal of the equal diameter section and exceeds a preset first threshold value, it is determined that the crystal raw material in the crucible is close to being fully melted; when the fluctuation of the compensated detection signal is lower than a preset second threshold value, it is determined that the crystal raw material has been completely melted, and the compensated detection signal at this time is recorded and recorded as signal one; (4) When all the crystal raw materials are melted, the heating power is kept constant, and the X-ray emitter and the X-ray receiver are moved downward by a distance equal to the diameter of the seed crystal, so that the X-ray emitter and the X-ray receiver are facing the upper end of the seed crystal. The X-ray detection signal of the upper end of the seed crystal is processed in real time by the software compensation method described in step (2), and the obtained signal is recorded as signal 2. When the difference between signal 2 and signal 1 is within the preset third threshold range, it is determined that the seed crystal has begun to melt. At this time, a certain amount of heating power should be reduced to maintain the state of the seed crystal unchanged and prevent the seed crystal from further melting, so as to realize the seeding process; then, the heating power is kept constant until the state of the crystal raw materials reaches a stable state, and the compensated detection signal at this time is recorded as signal 3; (5) Keeping the positions of the X-ray emitter and the X-ray receiver unchanged, the crucible is lowered at the set speed, and the signal values ​​at different positions of the crucible are continuously monitored by the X-ray emitter and the X-ray receiver, and the signal values ​​are processed in real time by the software compensation method described in step (2), and the processed signal values ​​are recorded as signal four, and the difference between signal four and signal three is calculated; a PID control algorithm is used to adjust the heater power of the growth zone in real time based on the difference, to ensure that the difference fluctuates within the set range, so that the crystallization rate is consistent with the crucible descent speed; at the same time, the heater power of the melting zone and the annealing zone is synchronously adjusted according to the preset process parameters, and finally a closed-loop control of the entire crystal growth process is achieved.

2. The closed-loop control method for crystal growth state according to claim 1, characterized in that: The X-ray output end of the X-ray emitter is provided with a collimating hole for generating a collimated X-ray beam with a reduced beam diameter.

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