A VB method indium phosphide crystal growth furnace and crystal growth method

Abstract

This invention discloses a VB method indium phosphide crystal growth furnace and crystal growth method. The apparatus includes a support frame, a pressure chamber, a double-layer crystal growth furnace assembly, a heating and temperature control assembly, and a lifting and rotating assembly. The pressure chamber is fixed to the top of the support frame and has a pressure chamber inside that matches the double-layer crystal growth furnace assembly. The lifting and rotating assembly includes a furnace body lifting unit and an inner furnace lifting and rotating unit. This invention, by setting up a double-layer furnace chamber and the spacing between the two quartz furnace chambers, ensures smooth displacement between the two quartz tubes. The upper part of the inner furnace chamber is sealed, and the lower part is inverted on the rotating support platform, forming a closed space between the inner and outer furnace chambers to reduce strong convection during crystal growth. The lower part of the inner chamber is a thermal field structure, and the upper part is the crystal growth space, promoting crystal growth in a stable environment and reducing defects caused by strong convection.

Description

Technical Field

[0001] This invention belongs to the technical field of crystal growth equipment, specifically relating to a VB method indium phosphide crystal growth furnace and crystal growth method. Background Technology

[0002] Indium phosphide possesses characteristics such as high saturated electron drift velocity, emission wavelength matching the low-loss communication band of optical fibers, strong radiation resistance, excellent thermal conductivity, high photoelectric conversion efficiency, and a large bandgap. It is not only a core substrate material in cutting-edge fields such as optical communication and interconnection, high-performance sensors, and high-end RF devices, but also an irreplaceable strategic core material in the AI ​​era.

[0003] In current technologies, crystal growth technology is weak, with numerous crystal defects and poor uniformity. Wafer processing capabilities are not yet mature, and the mainstream remains at the 2-3 inch process stage. High costs severely restrict the large-scale development of downstream industries. Large-size indium phosphide substrate materials still rely on imports, making supply chain security a bottleneck. At the equipment level, existing equipment is insufficient in terms of temperature field uniformity, pressure control precision, and automation level. In terms of crystal growth, mainstream products remain at the 2-3 inch wafer stage, and stable mass production of 4-inch and larger substrates has not yet been achieved. Furthermore, dislocation densities are generally high, and twinning and microtube defects occur frequently.

[0004] Currently, the growth of indium phosphide crystals mainly uses the VGF single crystal furnace and its method. This method keeps the relative position of the material and the heating zone constant, changes the heating power of the zone, forms an axial temperature gradient, and gradually cools down to solidify the melt into a crystal. The disadvantages are that the VGF method cannot promote crystal growth by precisely controlling the temperature of the furnace in different zones, the cooling rate of each stage of growth needs to be precisely optimized, the radial doping uniformity is low during crystal growth, twinning is easy to occur, resulting in very low utilization rate of the entire crystal or scrapping, and it is relatively difficult to grow a single crystal. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a VB method indium phosphide crystal growth furnace and crystal growth method to solve the technical problems of poor temperature field uniformity, high crystal dislocation density, numerous twin defects, and low doping uniformity in the growth of large-size indium phosphide crystals.

[0006] To achieve the above objectives, the specific technical solution of the present invention is as follows: In one aspect, there is a VB method indium phosphide crystal growth furnace, comprising a support frame, a pressure chamber, a double-layer crystal growth furnace assembly, a heating and temperature control assembly, and a lifting and rotating assembly.

[0007] The pressure chamber is fixed to the top of the support frame and has a pressure chamber inside that matches the double-layer crystal growth furnace assembly, which is used to provide the required pressure environment during crystal growth.

[0008] The lifting and rotating assembly includes a furnace body lifting unit and an inner furnace lifting and rotating unit. The double-layer crystal growth furnace assembly is installed on the lifting end of the furnace body lifting unit and can extend into or away from the pressure chamber under the drive of the furnace body lifting unit.

[0009] The inner furnace lifting and rotating unit is connected to the inner layer of the double-layer crystal growth furnace assembly, and can drive the inner layer of the double-layer crystal growth furnace assembly to rotate circumferentially and lift axially.

[0010] The heating and temperature control component is installed on the outer layer of the double-layer crystal growth furnace assembly and is used to supply heat to the inner layer.

[0011] Furthermore, the double-layer crystal growth furnace assembly includes a growth furnace body, an outer furnace chamber, an inner furnace chamber, a lower flange cover, a rotating support platform, a crucible, insulating filler, and multiple support pipes. The bottom of the growth furnace body is fixedly connected to the lifting end of the furnace body lifting unit via the lower flange cover. The outer furnace chamber and the inner furnace chamber are sequentially arranged within the inner cavity of the growth furnace body, spaced apart from each other. The outer furnace chamber is fixedly connected to the growth furnace body. The bottom of the inner furnace chamber is fixedly connected to the drive end of the inner furnace lifting and rotating unit via the rotating support platform, enabling it to be lifted, lowered, and rotated relative to the outer furnace chamber under the drive of the inner furnace lifting and rotating unit. Each support pipe is sequentially and spaced apart within the inner cavity of the inner furnace chamber. The crucible is coaxially mounted on the top of each support pipe. The insulating filler fills the gap between the outer and inner furnace chambers, as well as the inner cavity of the inner furnace chamber.

[0012] Furthermore, the inner furnace lifting and rotating unit includes a drive shaft, a lifting drive unit, and a rotating transmission unit. A clearance hole for the drive shaft is provided in the center of the lower flange cover. The drive shaft passes through the clearance hole on the lower flange cover, and its top end is fixedly connected to the bottom of the inner furnace chamber. The drive end of the lifting drive unit is threadedly connected to the power input end of the rotating transmission unit, enabling it to rotate while lifting. The power output end of the rotating transmission unit is rotatably connected to the drive shaft, enabling it to drive the inner furnace chamber to complete a circumferential rotation, while simultaneously cooperating with the lifting drive unit to achieve synchronous lifting of the drive shaft.

[0013] Furthermore, the lifting drive unit includes a second drive motor and a second ball screw. The second drive motor is fixed to the bottom surface of the lower flange cover by a bracket. The output shaft of the second drive motor is connected to the second ball screw, enabling it to drive the second ball screw synchronously during rotation. One end of the rotary transmission unit is threadedly connected to the second ball screw, and the other end is rotatably connected to the transmission shaft.

[0014] Furthermore, the rotary transmission unit includes a support transmission frame, a synchronous belt, and two synchronous pulleys. One end of the support transmission frame is threadedly connected to the second ball screw, and the other end is rotatably connected to the bottom of the transmission shaft. The two synchronous pulleys are rotatably connected to both ends of the support transmission frame, one of which is coaxially arranged with and threadedly connected to the second ball screw, and the inner ring of the other synchronous pulley is drivenly connected to the transmission shaft.

[0015] Furthermore, the insulating filler includes aluminum silicate blocks, graphite blocks, and quartz rods. The quartz rods are vertically positioned in the central region of the inner furnace chamber. The graphite blocks fill the bottom periphery of the quartz rods. The aluminum silicate blocks fill the space above the graphite blocks and the side gaps between the outer and inner furnace chambers.

[0016] Furthermore, the furnace body lifting unit includes a first drive motor and two first ball screws. The two first ball screws are vertically rotatably connected to the side of the support frame. The output shaft of the first drive motor is connected to the two first ball screws via a transmission synchronous belt assembly. Both ends of the lower flange cover are threadedly connected to the two ball screws respectively.

[0017] Furthermore, the pressure chamber includes an upper flange cover, a pressure gauge, and a chamber body. The chamber body is a cylindrical structure with both ends open. The upper flange cover is sealed to the upper opening of the chamber body by fixing bolts and nuts. The pressure gauge is mounted on the upper flange cover, and its sensing end extends into the pressure chamber.

[0018] Secondly, a crystal growth method for an indium phosphide crystal growth furnace using the VB method includes the following steps: Step S1: Furnace body assembly. Lower the lower flange cover to its lower limit position. Install the drive shaft, support pipe, inner furnace chamber, and outer furnace chamber sequentially within the main body of the growth furnace, and fill the designated positions with insulation filler in sequence.

[0019] Step S2: Material loading. A crucible containing indium phosphide crystal growth material is placed above the support tube. Then, the lower flange cover is moved towards the pressure chamber via the furnace lifting unit. When the lower flange cover rises to its upper limit position and abuts against the bottom of the pressure chamber, the second motor stops, and the sealing nut between the lower flange cover and the pressure chamber is tightened.

[0020] Step S3: Heat the furnace body. Heat the main body of the growth furnace according to the heating program to 300°C. Inert gas is introduced into the pressure chamber to raise the temperature of the main body of the growth furnace to between 1062 and 1080°C. The pressure during the material melting and growth process is maintained at 2.75-3 MPa.

[0021] Step S4, temperature-controlled growth: After the material melts, different temperatures are set for the high-temperature zone, gradient zone, and low-temperature zone. After maintaining a constant temperature for 2-8 hours, the inner furnace chamber and the crucible containing the crystals are synchronously rotated and lowered by the inner furnace lifting and rotating unit. The constant-diameter portion of the crystal gradually moves from the high-temperature zone to the low-temperature zone. During the crystal-leading stage, the rotation speed is 1-3 revolutions per minute, and the descent rate is 0.2-0.5 mm per hour; during the constant-diameter finishing stage, the rotation speed is 5-15 revolutions per minute, and the descent rate is 0.5-1.5 mm per hour; thus achieving slow crystallization of the indium phosphide melt, and finally the entire melt solidifies into crystals.

[0022] Step S5: Cooling and Demolding. Once all the crystals have descended to the low-temperature zone, the inner furnace lifting and rotating unit stops driving the crystals to rotate and descend. Start the cooling program and, after cooling is complete, vent the nitrogen from the furnace. Remove the sealing nut between the lower flange cover and the pressure chamber. Lower the double-layer crystal growth furnace assembly to a suitable height using the furnace lifting unit, remove the crucible from above, and then remove the crystals after opening the tubes.

[0023] Furthermore, in step S4, the temperature of the high-temperature zone is between 1065℃ and 1080℃, and the length is greater than 300mm; the temperature of the low-temperature zone is controlled between 1020℃ and 1050℃, and the length of the low-temperature zone is greater than 400mm; the length of the gradient zone is about 100mm, and the temperature gradually transitions from the high-temperature zone to the low-temperature zone, with the temperature gradient maintained at 0.2-0.8℃ / mm.

[0024] Compared with the prior art, the present invention has the following advantages: 1. This invention employs a double-layered furnace design, placing the outer furnace chamber close to the heating wire and filling the gap between them with high-purity alumina or quartz powder. This ensures uniform heat transfer to the furnace chamber. The spacing between the two quartz furnace layers ensures smooth displacement between the two quartz tubes. The upper part of the inner furnace chamber is sealed, while the lower part is inverted on a rotating support platform, forming a closed space that reduces intense convection during crystal growth. The lower part of the interior forms a thermal field structure, while the upper part serves as the crystal growth space, promoting crystal growth in a stable environment and minimizing defects caused by intense convection.

[0025] 2. By setting up an inner furnace lifting and rotating unit, the inner furnace chamber and crucible can be driven to rotate and descend synchronously, so that the crystal is heated more evenly during the crystallization process, effectively improving the radial doping uniformity, reducing the crystal dislocation density, and improving the overall quality of the crystal.

[0026] 3. The thermal insulation filler in this invention optimizes the thermal field structure for indium phosphide crystal growth through a thermal insulation structure combining graphite and aluminum silicate blocks. By adding a trapezoidal graphite of appropriate length to the center of the furnace core, the matching between the graphite blocks and the aluminum silicate blocks is adjusted. The temperature gradient of the seed crystal and the shoulder expansion position is adjusted according to the growth requirements, thereby reducing the generation of twins during the shoulder expansion process.

[0027] 4. By setting up a furnace body lifting unit and an inner furnace lifting and rotating unit, this invention can keep the position of the heating and temperature control components fixed throughout the entire crystal growth process. This eliminates the need for repeated disassembly and reassembly of the heating components and position adjustments, simplifying the loading and unloading operations and ensuring the consistency of the temperature field. This avoids the impact of temperature fluctuations on the stability of crystal growth. Combined with the rotating and descending action of the inner furnace chamber, it can more accurately control the crystal crystallization process, adapting to the stable growth requirements of large-size indium phosphide crystals of 4 inches and above. It effectively reduces the probability of defects such as twins and microtubes, and improves the yield and quality uniformity of the finished crystals. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the pressure cavity in this invention; Figure 3 This is a schematic diagram of the structure of the double-layer crystal growth furnace assembly in this invention; Figure 4 This is a schematic diagram of the furnace body lifting unit in this invention; Figure 5 This is a schematic diagram showing the relative positions of the lower flange cover and the inner furnace lifting and rotating unit in this invention. Figure 4 (Enlarged view of part A in the middle) Figure 6 This is a schematic diagram of the structure of the inner furnace lifting and rotating unit in this invention. Figure 5 (Enlarged view of part B in the middle section) Figure 7 This is a schematic diagram of the mechanical seal unit in this invention. Figure 5 (Enlarged view of part C in the middle) Figure 8 This is a schematic diagram of the structure of the double-layer crystal growth furnace assembly in the detached state in this invention.

[0029] Reference numerals: 1. Support frame; 2. Pressure chamber; 2-1. Upper flange cover; 2-2. Pressure gauge; 2-3. Chamber body; 3. Double-layer crystal growth furnace assembly; 4. Heating and temperature control assembly; 5. Furnace body lifting unit; 5-1. First drive motor; 5-2. First ball screw; 6. Inner furnace lifting and rotating unit; 6-1. Transmission shaft; 6-2. Lifting drive unit; 6-2-1. Second drive motor; 6-2-2. Second ball screw; 6-3. Rotation transmission unit; 7. Growth 8. Furnace body; 9. Outer furnace chamber; 10. Inner furnace chamber; 11. Lower flange cover; 12. Power cord terminal; 13. Thermocouple compensation wire terminal; 14. Rotating support platform; 15. Crucible; 16. Support tube; 17. Alumina silicate block; 18. Graphite block; 19. Quartz rod; 10. Mechanical seal unit; 11. Sealing mounting seat; 12. Sealing ring; 13. Bellows sealing sleeve; 14. Static graphite ring; 15. Dynamic graphite ring; 16. Conductive slip ring. Detailed Implementation

[0030] In the description of this invention, it should be understood that the terms "one end", "the other end", "outer side", "upper side", "inner side", "horizontal", "coaxial", "center", "end", "length", "outer end", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0031] The invention will now be further described with reference to the accompanying drawings.

[0032] like Figure 1 and 8 As shown, a VB method indium phosphide crystal growth furnace includes a support frame 1, a pressure chamber 2, a double-layer crystal growth furnace assembly 3, a heating and temperature control assembly 4, and a lifting and rotating assembly. The pressure chamber 2 is fixed to the top of the support frame 1 and has an internal pressure chamber that matches the double-layer crystal growth furnace assembly 3, providing the required pressure environment during crystal growth.

[0033] The lifting and rotating assembly includes a furnace body lifting unit 5 and an inner furnace lifting and rotating unit 6. The double-layer crystal growth furnace assembly 3 is mounted on the lifting end of the furnace body lifting unit 5 and can extend into or away from the pressure chamber under the drive of the furnace body lifting unit 5, and move up and down axially along the pressure chamber. The inner furnace lifting and rotating unit 6 is connected to the inner layer of the double-layer crystal growth furnace assembly 3 and can drive the inner layer of the double-layer crystal growth furnace assembly 3 to rotate circumferentially and move up and down axially.

[0034] The heating and temperature control component 4 is installed on the outer layer of the double-layer crystal growth furnace component 3 and is used to supply heat to the inner layer.

[0035] like Figure 2 As shown, the pressure chamber 2 includes an upper flange cover 2-1, a pressure gauge 2-2, and a chamber body 2-3. The chamber body 2-3 is a cylindrical structure with open ends. The upper flange cover 2-1 is sealed to the upper opening of the chamber body 2-3 by fixing bolts and nuts. The pressure gauge 2-2 is mounted on the upper flange cover 2-1, with its sensing end extending into the pressure chamber for real-time pressure monitoring.

[0036] like Figure 3 As shown, the double-layer crystal growth furnace assembly 3 includes a growth furnace body 7, an outer furnace chamber 8, an inner furnace chamber 9, a lower flange cover 10, a rotating support platform 11, a crucible 12, insulating filler, and multiple support pipes 13. The bottom of the growth furnace body 7 is fixedly connected to the lifting end of the furnace body lifting unit 5 via the lower flange cover 10, allowing it to extend into or away from the pressure chamber under the drive of the furnace body lifting unit 5. The outer furnace chamber 8 and the inner furnace chamber 9 are coaxially arranged in the inner cavity of the growth furnace body 7 from the outside in, with intervals between them. The outer furnace chamber 8 is fixedly connected to the growth furnace body 7. The bottom of the inner furnace chamber 9 is fixedly connected to the driving end of the inner furnace lifting and rotating unit 6 via the rotating support platform 11, allowing it to be lifted, lowered, and rotated relative to the outer furnace chamber 8 under the drive of the inner furnace lifting and rotating unit 6. The support pipes 13 are arranged in the inner cavity of the inner furnace chamber 9 with intervals between them. The crucible 12 is coaxially mounted on top of each support pipe 13 and is used to hold the indium phosphide raw material to be grown. Insulating filler is used to fill the gap between the outer furnace chamber 8 and the inner furnace chamber 9, as well as the inner cavity of the inner furnace chamber 9.

[0037] In this embodiment, the insulation filler includes aluminum silicate blocks 14, graphite blocks 15, and quartz rods 16. The quartz rods 16 are vertically positioned in the central region of the inner furnace chamber 9. The graphite blocks 15 fill the bottom periphery of the quartz rods 16, arranged in a stepped pattern with decreasing density from bottom to top. The aluminum silicate blocks 14 fill the space above the graphite blocks 15 and the side gaps between the outer furnace chamber 8 and the inner furnace chamber 9. Through the gradient arrangement of different insulation materials and the filling structure, the axial temperature gradient distribution inside the inner furnace chamber 9 is stably maintained, meeting the temperature field requirements for indium phosphide crystal growth.

[0038] In this embodiment, the gap between the outer furnace chamber 8 and the inner furnace chamber 9 is 0.5-1.5mm; the rotating support platform 11 is made of aluminum alloy.

[0039] like Figure 1 and 4As shown, the furnace body lifting unit 5 includes a first drive motor 5-1 and two first ball screws 5-2. The two first ball screws 5-2 are vertically rotatably connected to the side of the support frame 1. The output shaft of the first drive motor 5-1 is connected to the two first ball screws 5-2 via a transmission synchronous belt assembly, achieving synchronous rotation of the two ball screws. The two ends of the lower flange cover 10 are threadedly connected to the two ball screws, enabling the lower flange cover 10 to move up and down when the two ball screws rotate, thereby closing or opening the bottom opening of the pressure chamber 2.

[0040] like Figure 5 and 6 As shown, the inner furnace lifting and rotating unit 6 includes a drive shaft 6-1, a lifting drive unit 6-2, and a rotating transmission unit 6-3. A clearance hole for the drive shaft 6-1 is provided in the center of the lower flange cover 10. The drive shaft 6-1 passes through the clearance hole on the lower flange cover 10, and its top end is fixedly connected to the bottom of the inner furnace chamber 9. The drive end of the lifting drive unit 6-2 is threadedly connected to the power input end of the rotating transmission unit 6-3, enabling it to rotate while lifting. The power output end of the rotating transmission unit 6-3 is rotatably connected to the drive shaft 6-1, enabling the inner furnace chamber 9 to rotate circumferentially via the drive shaft 6-1, while simultaneously cooperating with the lifting drive unit 6-2 to achieve synchronous lifting of the drive shaft 6-1.

[0041] In this embodiment, the lifting drive unit 6-2 includes a second drive motor 6-2-1 and a second ball screw 6-2-2. The second drive motor 6-2-1 is fixed to the bottom surface of the lower flange cover 10 by a bracket. The output shaft of the second drive motor 6-2-1 is connected to the second ball screw 6-2-2, enabling it to drive the second ball screw 6-2-2 synchronously when rotating. One end of the rotary transmission unit 6-3 is threadedly connected to the second ball screw 6-2-2, and the other end is rotatably connected to the transmission shaft 6-1. When the output shaft of the second drive motor 6-2-1 rotates, it drives the second ball screw 6-2-2 to rotate. Through the rotary transmission unit 6-3, the transmission shaft 6-1 is driven to lift synchronously, thereby realizing the axial position adjustment of the inner furnace 9. At the same time, the rotary transmission unit 6-3 can drive the transmission shaft 6-1 to rotate, thereby driving the inner furnace 9 to rotate synchronously circumferentially. Combined with the stepped axial temperature distribution of the heating and temperature control component 4, the indium phosphide melt slowly cools and crystallizes, and finally the entire melt solidifies into crystals.

[0042] Furthermore, the rotary transmission unit 6-3 includes a support transmission frame, a synchronous belt, and two synchronous pulleys. One end of the support transmission frame is threadedly connected to the second ball screw 6-2-2, and the other end is rotatably connected to the bottom of the transmission shaft 6-1. The two synchronous pulleys are rotatably connected to both ends of the support transmission frame. One synchronous pulley is coaxially arranged with and threadedly connected to the second ball screw 6-2-2, while the inner ring of the other synchronous pulley is drively connected to the transmission shaft 6-1, enabling it to drive the transmission shaft 6-1 to rotate synchronously during rotation. The two synchronous pulleys are connected by a synchronous belt.

[0043] In this embodiment, the present invention provides a non-essential technical feature: a vertical mounting groove is provided on the inner ring of the synchronous pulley that is connected to the drive shaft 6-1. A drive pin is fixedly engaged in the mounting groove. A vertical slot is provided on the drive shaft 6-1 to cooperate with the drive pin, and the drive pin extends into the vertical slot.

[0044] Furthermore, the heating and temperature control component 4 includes a furnace heating wire and temperature-sensing thermocouples. The furnace heating wire is positioned in the gap between the outer furnace chamber 8 and the inner wall of the growth furnace body 7, providing stable heat to the inner furnace chamber 9. The temperature on the furnace heating wire decreases progressively from top to bottom, creating a high-temperature zone, a gradient zone, and a low-temperature zone sequentially on the outer furnace chamber 8. This provides a stable axial temperature gradient for the indium phosphide crystal growth process, meeting the requirements for gradual crystal growth. The temperature-sensing thermocouples are spaced axially at the bottom of the inner furnace chamber 9, with their sensing ends extending into the inner furnace chamber 9. This allows for real-time acquisition of temperature data at different locations within the inner furnace chamber 9, facilitating precise temperature control laterally.

[0045] In this embodiment, graphite heating wire is used for the furnace body. High-purity alumina powder or quartz powder is filled between the outer furnace chamber 8 and the furnace body heating wire to ensure uniform heat transfer to the furnace chamber.

[0046] Furthermore, a conductive slip ring 18 is provided between the furnace heating wire and the lower flange cover 10 to provide a stable power and signal transmission path for the wiring of the heating wire and thermocouple, while preventing the wiring from becoming tangled or pulled during the raising and lowering of the lower flange cover 10. Specifically, the conductive slip ring 18 is sleeved on the outer ring of the drive shaft 6-1, and the inner ring of the conductive slip ring 18 is fixedly connected to the drive shaft 6-1, while the outer ring is fixedly connected to the lower flange cover 10. One end of the conductive slip ring 18 is connected to the temperature-sensing thermocouple via a wire, and the other end is connected to an external signal receiver via a wire, stably transmitting the temperature signal to the control system.

[0047] In this embodiment, the lower flange cover 10 has a gas connection connector, a power supply terminal 10-1, and a thermocouple compensation terminal 10-2 at its edge. The gas connection connector connects to the pressure chamber and is used to fill the pressure chamber with protective gas to maintain the pressure environment required for the crystal growth process. The power supply terminal 10-1 provides power to the furnace heating wire to ensure stable heating operation. The thermocouple compensation terminal 10-2 is connected to the conductive slip ring 18 via a wire and is used to transmit the temperature signal collected by the thermocouple to the external control system to achieve precise temperature control of the growth process.

[0048] Furthermore, such as Figure 7 As shown, a mechanical seal unit 17 is provided between the drive shaft 6-1 and the lower flange cover 10 to achieve an integrated seal between the drive shaft 6-1 and the lower flange cover 10. Specifically, the mechanical seal unit 17 includes a sealing mounting seat 17-1, sealing rings 17-2, a bellows sealing sleeve 17-3, a static graphite ring 17-4, and a dynamic graphite ring 17-5. The sealing mounting seat 17-1 is fixed in the clearance hole of the lower flange cover 10. Multiple sealing rings 17-2 are disposed between the sealing mounting seat 17-1 and the lower flange cover 10, and between the sealing mounting seat 17-1 and the drive shaft 6-1. The bellows sealing sleeve 17-3 is fitted onto the outer ring of the drive shaft 6-1, and its two ends abut against the static graphite ring 17-4 and the dynamic graphite ring 17-5, respectively. The elastic deformation of the bellows sealing sleeve 17-3 compensates for the gap during the rotation and lifting process of the drive shaft 6-1, thereby preventing pressure leakage during vertical movement and rotation under high pressure.

[0049] A method for growing indium phosphide crystals using the VB method includes the following steps: Step S1: Furnace body assembly. Lower the lower flange cover 10 to its lower limit position. Within the main body 7 of the growth furnace, sequentially install the drive shaft 6-1, support pipe 13, inner furnace chamber 9, and outer furnace chamber 8, and then sequentially fill the designated positions with insulation filler. Specific steps are as follows: In step S1-1, insert the drive shaft 6-1 into the clearance hole of the lower flange cover 10, and pass it through the conductive slip ring. Its top end is fixedly connected to the rotating support platform 11 fixed to the bottom of the inner furnace chamber 9, and its bottom end is connected to the inner furnace lifting and rotating unit 6. Then, install the outer conductive slip ring 18 onto the drive shaft 6-1. Fix the inner ring of the conductive slip ring 18 to the drive shaft 6-1, and fix the outer ring to the lower flange cover 10.

[0050] Step S1-2: Insert each support tube 13, inner furnace chamber 9, and outer furnace chamber 8 into the main body 7 of the growth furnace in sequence.

[0051] Steps S1-3: Graphite blocks 15 and aluminum silicate blocks are sequentially inserted into the inner cavities of each support tube 13 from the inside out.

[0052] Step S2: Material loading. A crucible 12 containing indium phosphide crystal growth material is placed above the support tube 13. The inner furnace chamber 9 and the rotating support platform 11 form a sealed enclosure for the graphite block 15, quartz rod 16, support tube 13, aluminum silicate block, and crucible 12 containing the material. This prevents external gas convection from affecting the internal crystal growth.

[0053] Subsequently, after completing the wiring of the temperature measuring thermocouple and checking that the second motor is operating normally, the first motor is started. The first motor drives the lower flange cover 10 to move towards the pressure chamber 2. When the lower flange cover 10 rises to its upper limit position and abuts against the bottom of the pressure chamber 2, the second motor is stopped, the sealing nut between the lower flange cover 10 and the pressure chamber 2 is tightened, and the connection is checked for any abnormalities. This ensures that there are no abnormalities in the temperature signal, power line connection, or sealing in the double-layer crystal growth furnace assembly 3.

[0054] In this embodiment, the crucible 12 containing the material is installed into the inner furnace 9, which has a sealed end, from top to bottom. Step S3: Heat the furnace body according to the heating program. When the temperature reaches 300°C, fill the cavity with inert gas and heat it to above the melting point of indium phosphide to promote the complete melting of the crystal growth material. The temperature of the melting part above the seed crystal is between 1062 and 1080°C, which can be finely adjusted according to the process. The pressure during the material melting and growth process is maintained at 2.75-3 MPa.

[0055] Step S4, temperature-controlled growth: After the material melts, different temperatures are set for the high-temperature zone, gradient zone, and low-temperature zone. Initially, the high-temperature zone is located above the constant-diameter portion of the crystal (the entire crystal growth process begins as a small cylindrical rod of about 1cm. One end of the rod gradually cools, transforming from liquid to solid, and the diameter of one end of the 1cm rod gradually expands to about 12cm. During subsequent cooling, the diameter no longer expands and remains at 12cm. The 1cm portion is called the seed crystal portion, the diameter-expanding portion is called the shoulder portion, and the 12cm portion is called the constant-diameter portion). The low-temperature zone is located below the seed crystal portion. The gradient zone is located between the high-temperature zone and the low-temperature zone, serving as a transition between the two zones, and the temperature of each zone is adjusted accordingly.

[0056] Following the pre-set gradient, after maintaining a constant temperature for 2-8 hours, the second motor is activated. The second motor drives the transmission shaft 6-1 to slowly rotate and descend, simultaneously driving the rotating support platform 11, the inner furnace chamber 9 on the rotating support platform 11, and the crucible 12 containing the crystal to rotate and descend synchronously. The constant-diameter portion of the crystal gradually moves from the high-temperature zone to the low-temperature zone. During the crystal-leading stage, the rotation speed is 1-3 revolutions per minute, and the descent rate is 0.2-0.5 mm per hour; during the constant-diameter finishing stage, the rotation speed is 5-15 revolutions per minute, and the descent rate is 0.5-1.5 mm per hour; thus achieving the slow crystallization of the indium phosphide melt, and finally the entire melt solidifies into crystals.

[0057] In this embodiment, the crucible 12 has a conical structure that is larger at the top and smaller at the bottom. The upper part of the container is a large-diameter cavity, the lower part of the crucible 12 is a small-diameter cavity, and the middle part gradually expands into a larger cavity. In actual operation, a relatively small indium phosphide single crystal rod is first placed in the small cavity at the bottom of the crucible 12. Then, indium phosphide material is placed in the middle and upper parts of the crucible 12. The temperature is raised to melt the indium phosphide material, and the upper half of the lower indium phosphide single crystal rod melts. The molten indium phosphide material comes into contact with the single crystal rod to form a solid-liquid interface. The temperature at the bottom gradually decreases, and the material at the solid-liquid interface gradually solidifies into a solid single crystal. As the temperature gradually decreases, the solid-liquid interface gradually moves upward. During the movement, the diameter of the single crystal gradually increases. The solidification stage in the small cavity is called the crystal-initiating stage, the stage of gradually increasing diameter is called the shoulder-expanding stage, the stage where the diameter reaches its maximum and remains constant is called the constant-diameter stage, and the stage where all the material solidifies into a solid is called the finishing stage.

[0058] In this embodiment, the temperature of the high-temperature zone is between 1065℃ and 1080℃, and the length is greater than 300mm. The temperature of the low-temperature zone is controlled between 1020℃ and 1050℃, and the length of the low-temperature zone is greater than 400mm. The length of the gradient zone is about 100mm, and the temperature gradually transitions from the temperature of the high-temperature zone to the temperature of the low-temperature zone, with the temperature gradient maintained at (0.2-0.8)℃ / mm.

[0059] Step S5: Cooling and Demolding. Once all the crystals have descended to the low-temperature zone, the second motor stops driving the crystals to rotate and descend. The cooling program is started, and after a cooling process of 15-25℃, the crystal temperature drops below 100℃. The nitrogen gas in the furnace is vented, the sealing nut between the lower flange cover 10 and the pressure chamber 2 is removed, the first motor is started, and the double-layer crystal growth furnace assembly 3 descends to a suitable height. The crucible 12 is then removed from above, and the crystals are taken out after the tube is opened.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A VB method indium phosphide crystal growth furnace, characterized in that: Includes a support frame, pressure chamber, double-layer crystal growth furnace assembly, heating and temperature control assembly, and lifting and rotating assembly; The pressure chamber is fixed to the top of the support frame and has a pressure chamber inside that matches the double-layer crystal growth furnace assembly, which is used to provide the required pressure environment during crystal growth. The lifting and rotating assembly includes a furnace body lifting unit and an inner furnace lifting and rotating unit; the double-layer crystal growth furnace assembly is installed on the lifting end of the furnace body lifting unit and can extend into or away from the pressure chamber under the drive of the furnace body lifting unit. The inner furnace lifting and rotating unit is connected to the inner layer of the double-layer crystal growth furnace assembly, and can drive the inner layer of the double-layer crystal growth furnace assembly to rotate circumferentially and lift axially. The heating and temperature control component is installed on the outer layer of the double-layer crystal growth furnace assembly and is used to supply heat to the inner layer.

2. The indium phosphide crystal growth furnace according to claim 1, characterized in that: The double-layer crystal growth furnace assembly includes a growth furnace body, an outer furnace chamber, an inner furnace chamber, a lower flange cover, a rotating support platform, a crucible, insulating filler, and multiple support pipes. The bottom of the growth furnace body is fixedly connected to the lifting end of the furnace body lifting unit via the lower flange cover. The outer furnace chamber and the inner furnace chamber are sequentially arranged in the inner cavity of the growth furnace body, with intervals between them. The outer furnace chamber is fixedly connected to the growth furnace body. The bottom of the inner furnace chamber is fixedly connected to the drive end of the inner furnace lifting and rotating unit via the rotating support platform, enabling it to be lifted, lowered, and rotated relative to the outer furnace chamber under the drive of the inner furnace lifting and rotating unit. Each support pipe is sequentially and spaced apart in the inner cavity of the inner furnace chamber. The crucible is coaxially mounted on the top of each support pipe. The insulating filler fills the gap between the outer furnace chamber and the inner furnace chamber, as well as the inner cavity of the inner furnace chamber.

3. The indium phosphide crystal growth furnace according to claim 2, characterized in that: The inner furnace lifting and rotating unit includes a drive shaft, a lifting drive unit, and a rotating transmission unit. A clearance hole is provided in the center of the lower flange cover to mate with the drive shaft. The drive shaft passes through the clearance hole on the lower flange cover, and its top end is fixedly connected to the bottom of the inner furnace chamber. The drive end of the lifting drive unit is threadedly connected to the power input end of the rotating transmission unit, enabling it to rotate while being lifted. The power output end of the rotating transmission unit is rotatably connected to the drive shaft, enabling it to drive the inner furnace chamber to complete a circumferential rotation, while simultaneously cooperating with the lifting drive unit to achieve synchronous lifting of the drive shaft.

4. The VB method indium phosphide crystal growth furnace according to claim 3, characterized in that: The lifting drive unit includes a second drive motor and a second ball screw; the second drive motor is fixed to the bottom surface of the lower flange cover by a bracket; the output shaft of the second drive motor is connected to the second ball screw, and can drive the second ball screw to connect synchronously when rotating; one end of the rotary transmission unit is threadedly connected to the second ball screw, and the other end is rotatably connected to the transmission shaft.

5. The indium phosphide crystal growth furnace according to claim 3, characterized in that: The rotary transmission unit includes a support transmission frame, a synchronous belt, and two synchronous pulleys; one end of the support transmission frame is threadedly connected to the second ball screw, and the other end is rotatably connected to the bottom of the transmission shaft; the two synchronous pulleys are rotatably connected to the two ends of the support transmission frame, one of which is coaxially arranged with the second ball screw and threadedly connected to it, and the inner ring of the other synchronous pulley is connected to the transmission shaft.

6. The indium phosphide crystal growth furnace according to claim 2, characterized in that: The insulation filler includes aluminum silicate blocks, graphite blocks, and quartz rods; the quartz rods are vertically arranged in the central area of ​​the inner furnace chamber; the graphite blocks are filled around the bottom of the quartz rods; the aluminum silicate blocks are filled above the graphite blocks and in the side gaps between the outer and inner furnace chambers.

7. The indium phosphide crystal growth furnace according to claim 1, characterized in that: The furnace body lifting unit includes a first drive motor and two first ball screws; the two first ball screws are vertically rotatably connected to the side of the support frame; the output shaft of the first drive motor is connected to the two first ball screws through a transmission synchronous belt assembly; the two ends of the lower flange cover are threadedly connected to the two ball screws respectively.

8. The indium phosphide crystal growth furnace according to claim 1, characterized in that: The pressure chamber includes an upper flange cover, a pressure gauge, and a chamber body. The chamber body is a cylindrical structure with both ends open. The upper flange cover is sealed to the upper opening of the chamber body by fixing bolts and nuts. The pressure gauge is installed on the upper flange cover, and the detection end extends into the pressure chamber.

9. The crystal growth method of the indium phosphide crystal growth furnace according to claim 2, characterized in that: Includes the following steps: Step S1: Furnace body assembly. Lower the lower flange cover to the lower limit position. Install the drive shaft, support pipe, inner furnace chamber and outer furnace chamber in sequence inside the growth furnace body, and fill the insulation filler into the designated position in sequence. Step S2: Material loading into the furnace. A crucible containing indium phosphide crystal growth material is placed above the support tube. Then, the lower flange cover is driven to move towards the pressure chamber via the furnace body lifting unit. When the lower flange cover rises to the upper limit position and abuts against the bottom of the pressure chamber, the second motor is stopped, and the sealing nut between the lower flange cover and the pressure chamber is locked. Step S3: Heat the furnace body. Heat the main body of the growth furnace according to the heating program to 300°C. Inert gas is introduced into the pressure chamber to raise the temperature of the main body of the growth furnace to between 1062 and 1080°C. The pressure during the material melting and growth process is maintained at 2.75-3 MPa. Step S4, temperature-controlled growth: After the material melts, different temperatures are set according to the high-temperature zone, gradient zone, and low-temperature zone. After maintaining the temperature for 2-8 hours, the inner furnace chamber and the crucible containing the crystals are synchronously rotated and lowered by the inner furnace lifting and rotating unit. The constant-diameter portion of the crystal gradually moves from the high-temperature zone to the low-temperature zone. During the crystal-leading stage, the rotation speed is 1-3 revolutions per minute, and the descent rate is 0.2-0.5 mm per hour. During the constant-diameter finishing stage, the rotation speed is 5-15 revolutions per minute, and the descent rate is 0.5-1.5 mm per hour. This achieves the slow crystallization of the indium phosphide melt, and finally the entire melt solidifies into crystals. Step S5, cooling and demolding: After all the crystals have descended to the low temperature zone, the inner furnace lifting and rotating unit stops driving the crystals to rotate and descend; the cooling program is started, and after cooling is completed, the nitrogen in the furnace is vented, and the sealing nut between the lower flange cover and the pressure chamber is removed; the double-layer crystal growth furnace assembly is lowered to a suitable height through the furnace lifting unit, the crucible is taken out from the top, and the crystal is taken out after the tube is opened.

10. The crystal growth method of the indium phosphide crystal growth furnace according to claim 9, characterized in that: In step S4, the temperature of the high-temperature zone is between 1065℃ and 1080℃, and the length is greater than 300mm. The temperature of the low-temperature zone is controlled between 1020℃ and 1050℃, and the length of the low-temperature zone is greater than 400mm. The length of the gradient zone is about 100mm, and the temperature gradually transitions from the high-temperature zone to the low-temperature zone, with the temperature gradient maintained at 0.2-0.8℃ / mm.

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