Method for growing curved crystal using edge-defined film-fed growth

Abstract

Disclosed in the present invention is a method for growing a curved crystal using edge-defined film-fed growth, comprising: S1: placing a growth material in a crucible, placing a mold in the crucible, and placing a seed crystal 3-50 mm directly above the mold by means of a seed crystal rod, the mold being provided with a curved cavity; S2: vacuumizing an upper thermal insulation device and a middle thermal insulation device, and filling the upper thermal insulation device and the middle thermal insulation device with an inert gas; S3: performing exhaust treatment; S4: raising the temperature in the crucible to a first temperature to melt the growth material in the crucible; S5: bringing the seed crystal into contact with the mold, raising the temperature to a second temperature, and pulling the seed crystal; S6: necking the seed crystal, pulling same over a length of 5-10 mm, and performing primary cooling; S7: separating a crystal from the mold; and S8: performing annealing treatment after cooling. The growth method provided by the present invention provides a uniform heated space for the growth of the crystal, controls the release of the growth stress and thermal stress of the crystal, and implements exhausting to remove impurities volatilized from the interiors of the thermal insulation devices; and a curved crystal is grown by bringing the seed crystal into contact with the curved cavity of the mold, thereby reducing cutting and rough processing costs.

Description

A Guided Model Method for Growing Curved Crystals

[0001] This application claims priority to Chinese Patent Application No. 202411844095.5, filed on December 15, 2024, entitled "A Guided-Modification Method for Growing Curved Crystals", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of crystal growth technology, and more specifically to a method for growing curved surface crystals using a guided model. Background Technology

[0003] Sapphire is a single crystal of aluminum oxide, a material with excellent physical, chemical, and optical properties. Due to its unique optical and physical properties, sapphire is used as a substrate for light-emitting diodes (LEDs) and sapphire epitaxial wafers (SOS) because of its lattice matching and good thermal properties. Sapphire also possesses advantages such as high thermal conductivity, high melting point, and high mechanical strength, making it suitable for applications in front-end lasers, gravitational wave interferometers, transparent armor, infrared window materials, and other industrial, civilian, and wearable consumer electronics products.

[0004] There are several methods for growing sapphire crystals, including the KY method (Czochralski method), the Cz method (Czochralski method), the EFG method (Fake method), and the HEM method (Heat exchange method). Traditional Fake methods are basically used to grow planar crystals. Since the thickness of the grown planar crystals is thin, usually within 20mm, it is difficult to process curved sapphire crystals.

[0005] While sapphire ingots grown using the Czochralski method can be used for machining curved sapphire crystals, the process presents challenges related to complex cutting and roughing techniques and high costs. For large-sized curved sapphire crystals, ingots prepared using the Czochralski method are currently insufficient for sourcing. Therefore, developing curved sapphire crystals and significantly reducing the costs and risks associated with initial cutting and roughing are key issues that need to be addressed. Summary of the Invention

[0006] To address the above problems, this invention provides a guided-mold method for growing curved crystals, which can directly grow curved sapphire crystals.

[0007] This invention provides a method for growing curved surface crystals using the guided-mode method, comprising:

[0008] S1: Place the growth material into the crucible, place the mold into the crucible, fix the seed crystal at one end of the seed crystal rod, and connect the seed crystal rod to the lifting mechanism; place the seed crystal through the seed crystal rod at a position 3-50mm directly above the mold, and the mold has a curved inner cavity; the crucible is located in the middle heat preservation device, and part or all of the seed crystal and the seed crystal rod are located in the upper heat preservation device.

[0009] S2: Evacuate the upper and middle insulation devices and then fill them with inert gas;

[0010] S3: Perform exhaust treatment;

[0011] S4: Raise the temperature inside the crucible to the first temperature to melt the raw materials growing inside the crucible;

[0012] S5: After the seed crystal is lowered to contact the upper surface of the mold by the seed crystal rod, the temperature inside the crucible is raised to the second temperature again, and then the seed crystal is pulled up by the seed crystal rod.

[0013] S6: When the seed crystal is reduced in diameter and pulled up by 5-10mm, and the reduced diameter of the seed crystal is 1 / 3 to 1 / 2 of the original size of the seed crystal, start the first cooling process. Stop cooling when the width of the grown crystal is the same as the width of the mold, and record the internal temperature T1 of the mold.

[0014] S7: The crystal continues to grow. After the crystal reaches the same diameter, the temperature is adjusted based on the temperature of T1 using data fed back from the sensor. After the crystal growth is completed, the temperature is T2. The entire crystal is then removed from the mold.

[0015] S8: Annealing is performed after cooling.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: by placing the growth raw material and seed crystal into the crucible and placing the mold in the crucible, a uniform heating space is provided for the growth of the crystal, the growth stress and thermal stress of the crystal are controlled, and cracking after the crystal cools down or cracking due to excessive stress during the processing is avoided. Uneven heating of the crystal during the growth process can also be avoided, resulting in deformation of the crystal surface and high flatness of the finished crystal, thus reducing the amount of grinding and polishing required.

[0017] Vacuuming and filling the upper and middle insulation devices with inert gas effectively suppresses the oxidation and volatilization of the heater and insulation materials after heating, preventing contamination of the growth raw materials by oxidation and volatilization. Exhausting the gas removes impurities released from internal components of the insulation devices, thereby improving crystal quality. After the raw material is melted, the seed crystal contacts the curved cavity of the mold, thus growing curved crystals, avoiding complex cutting and rough machining techniques and reducing cost waste.

[0018] By using a mold with a curved inner cavity to control the first temperature, the second temperature, and the internal temperatures T1 and T2 of the mold, and by combining this with a reasonable pulling speed, microbubbles inside the crystal are controlled to be confined to a small portion of the crystal surface, thus improving the growth quality of the crystal.

[0019] When the crystal shoulder is grown to the same width as the mold, constant diameter growth is performed. After constant diameter growth is completed, the crystal is separated from the mold and then annealed. This process can produce curved sapphire crystals with a short growth cycle. Curved crystals that can be directly grown to meet the requirements of direct grinding and polishing can be obtained, which greatly reduces the cost of early cutting and roughing.

[0020] Furthermore, the upper surface of the mold has a V-shaped opening with an angle of 90°-180°. The distance between the lower surface of the mold and the bottom of the crucible is 0-50mm. When the distance between the lower surface of the mold and the bottom of the crucible is 0mm, a through hole connecting the crucible and the interior of the mold is provided on the side of the mold at a position 0-20mm from the lower surface. The present invention does not impose a particular limitation on the number of the aforementioned through holes, which can be adjusted according to actual needs, as long as the purpose of the present invention can be achieved.

[0021] The beneficial effects of adopting the above-mentioned further technical solution are as follows: By setting a V-shaped opening with an angle of 90°-180° on the upper surface of the mold, the temperature of the crystal growing in the middle can be avoided from being lower than that of the crystals growing on both sides, allowing the crystal to grow under uniform heating. The growth material enters the interior of the mold through the gap or through hole between the lower surface of the mold and the bottom surface of the crucible, and is transported to the upper surface of the mold by capillary action. When the distance between the lower surface of the mold and the bottom surface of the crucible is greater than 0, the mold separates from the melt in the crucible after the crystal growth is completed, which helps to extend the life of the crucible.

[0022] Furthermore, the crucible and the first heating device are disposed within the cavity of the middle heat preservation device, with the first heating device located outside the crucible and the second heating device disposed within the cavity of the upper heat preservation device. The crucible, the first heating device, the second heating device, the middle heat preservation device, and the upper heat preservation device all have an arc-shaped structure. The inner surfaces of the crucible cavity, the first heating device cavity, the second heating device cavity, the middle heat preservation device cavity, and the upper heat preservation device cavity are all arc surfaces. The aforementioned inner surfaces refer to the inner sides of the cavities. A lower heat preservation device is connected below the middle heat preservation device, and a power supply device is disposed within the lower heat preservation device. Both the first heating device and the second heating device are electrically connected to the power supply device.

[0023] The beneficial effects of adopting the above-mentioned further technical solution are as follows: by making the crucible, the first heating device, the second heating device, the middle heat preservation device and the upper heat preservation device into arc-shaped structures, and the interior of the cavity into an arc surface, the temperature field of the curved crystal can meet the requirements of crystal growth, avoid uneven crystal temperature leading to local overcooling and crystal growth failure, realize the rapid heat transport direction and heat transport control in crystal growth, grow high-quality crystals with shallow bubble layers and smooth surfaces, reduce the amount of grinding and polishing of finished crystals, and achieve the growth of curved sapphire crystals.

[0024] Furthermore, the growth material in S1 is alumina.

[0025] Furthermore, in step S2, a vacuum is drawn to below 10 Pa, and the inert gas is argon or nitrogen; the flow rate of the inert gas is 0.5-5 L / min.

[0026] The beneficial effects of adopting the above-mentioned further technical solution are as follows: by filling with argon and nitrogen gas at a pressure below 10 Pa, the oxidation and volatilization of the heater and insulation material after heating are effectively suppressed, thus avoiding the pollution of the growth raw materials by oxidation and volatilization.

[0027] Furthermore, the exhaust process in S3 is as follows: exhaust is performed on the upper and lower insulation devices, and exhaust is stopped when the gas pressure is lower than 1kPa-100kPa.

[0028] Furthermore, in step S4, the temperature inside the crucible is raised to a first temperature by the first heating device, the heating time to the first temperature is 4-10 hours, the heating rate is 80-300℃ / h, the first temperature is 2050-2200℃, and the temperature is maintained at 2050-2200℃ for 5-35 minutes; during step S4, the temperature inside the upper heat preservation device is controlled to be 1750-1900℃ by the second heating device.

[0029] Furthermore, in S5, the second temperature is 20-150°C higher than the first temperature. After reaching the second temperature, the temperature is maintained for 5-60 minutes, and then the seed crystal is pulled up by the seed crystal rod at a pulling speed of 5-100 mm / h. During S5, the temperature inside the upper heat preservation device is controlled to be 1800-2000°C by the second heating device.

[0030] The beneficial effects of adopting the above-mentioned further technical solution are as follows: When the temperature reaches the first temperature, the energy provided by the heater melts the alumina raw material in the crucible into a melt. During process S4, the temperature inside the upper holding device is controlled at 1750-1900℃ by the second heating device, which can control the temperature of the seed crystal in the holding device to be close to that of the crucible, while preventing the seed crystal from melting. By raising the temperature by 20-150℃ to reach the second temperature, a liquid film is formed between the melted seed crystal and the melted growth raw material, thereby driving crystal growth. By pulling the seed crystal to reduce its diameter, the risk of introducing defects from the seed crystal into the crystal is reduced, thus improving the growth quality of the crystal. During process S5, the temperature inside the upper holding device is controlled at 1800-2000℃ by the second heating device, making the seed crystal temperature close to the crystal growth temperature, which is beneficial to crystal growth during the pulling process.

[0031] Furthermore, in step S6, the cooling rate for each cooling step is 1-50℃ / h; the internal temperature T1 of the mold is recorded; in step S7, after crystal growth is completed, the temperature is kept at T2+10℃ for 10-20 minutes, and then the crystal is pulled out of the mold at a pulling speed of 900-1100mm / h using a seed crystal rod at the internal temperature T2+10℃. The beneficial effects of adopting the above further technical solution are: by reducing the diameter, the crystal is gradually sized to the same width as the mold for constant-diameter growth. After entering the constant-diameter stage, the growth rate of the crystal is determined by a weight sensor, and the crystal growth process is completed by controlling the growth rate, which helps to improve crystal quality. This invention does not have any particular limitations on the method of controlling the growth rate, as long as it achieves the purpose of this invention. For example, it can be adjusted by adjusting the internal crystal growth temperature of the mold or the pulling speed of the seed crystal during the crystal growth process.

[0032] Furthermore, in step S8, after the crystal detaches from the mold, the temperature of the middle heat-preserving device is lowered by stopping the heating of the first and second heating devices, resulting in a temperature reduction of 180-220°C from the temperature at which the crystal detached from the mold. Similarly, the temperature inside the upper heat-preserving device is lowered by stopping the heating of the first and second heating devices, resulting in a temperature reduction of 160-180°C from the temperature at which the crystal detached from the mold. After cooling and heat preservation for 1-4 hours, annealing is completed. After annealing, the heating power of the first and second heating devices is reduced, and the temperature is lowered at rates of 100-400°C / h and 80-100°C / h, respectively. The crystal is then left to stand for 10-24 hours before being removed. The aforementioned cooling rate can be controlled by adjusting the degree of reduction in heating power; this invention does not impose any particular limitation on this, as long as the objective of this invention is achieved. The beneficial effects of adopting the above-mentioned further technical solution are as follows: after the crystal is pulled out of the mold, the crystal growth is completed and the temperature is lowered. After cooling, the temperature is maintained for a period of time to allow the crystal to enter the annealing state, eliminating the internal stress and growth defects of the crystal. After cooling, the crystal is taken out, which can directly grow crystals that can meet the requirements of direct grinding and polishing, greatly reducing material waste and effectively reducing costs.

[0033] The chord length of the curved crystal obtained by the growth method provided in this invention can be 10-700 mm, and the chord height can be 5-100 mm. The curved inner cavity of the mold in this invention is determined according to the required chord length and chord height of the curved crystal; this invention does not impose any particular limitation on these, as long as the objective of this invention can be achieved. This invention does not impose any particular limitation on the shape of the seed crystal; shapes commonly used in the art can be adopted.

[0034] The sensors described in S7 include a weight sensor and a temperature sensor. The temperature sensor is used to monitor the temperature inside the mold during crystal growth, and the weight sensor is used to monitor the crystal growth rate. This invention does not have any particular limitations on these, as long as the purpose of this invention can be achieved.

[0035] In this invention, the materials of the first heating device, the second heating device, the middle heat preservation device, and the upper heat preservation device can be at least one of graphite, tungsten, molybdenum, zirconium oxide, rhenium, and iridium, and the materials of the mold and the crucible can be at least one of tungsten, molybdenum, rhenium, and iridium. Attached Figure Description

[0036] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0037] Figure 1 shows a cross-sectional view of the growth apparatus for curved surface crystal growth using the guided mold method;

[0038] Figure 2 is a cross-sectional view of the upper heat preservation device, the second heating device, and the crystal along the horizontal direction;

[0039] Figure 3 is a cross-sectional view of the central heat preservation device, the first heating device, the crucible, and the mold along the horizontal direction.

[0040] Reference numerals in the attached drawings: 1. Crucible; 2. Mold; 3. Seed crystal; 4. Crystal; 5. Seed crystal rod; 6. Upper heat preservation device; 61. Second heating device; 7. Middle heat preservation device; 71. First heating device; 8. Lower heat preservation device; 81. Power supply device. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0042] Example

[0043] In embodiments one to three of this invention, the growth apparatus shown in Figure 1 is used to grow curved crystals. A cross-sectional view of the growth apparatus is shown in Figure 1. This growth apparatus includes an upper heat-preserving device 6, a middle heat-preserving device 7, and a lower heat-preserving device 8. A second heating device 61 is located within the cavity of the upper heat-preserving device 6, and a first heating device 71 and a crucible 1 are located within the cavity of the middle heat-preserving device 7. The first heating device 71 is disposed outside the crucible 1. The middle heat-preserving device 7 is connected below the upper heat-preserving device 6, and the lower heat-preserving device 8 is connected below the middle heat-preserving device 7. A power supply device 81 is disposed within the lower heat-preserving device 8. Both the first heating device 71 and the second heating device 61 are electrically connected to the power supply device 81. The mold 2 is located inside the crucible 1, and the seed crystal 3 is fixed to the lower end of the seed crystal rod 5; the seed crystal 3 is positioned directly above the mold 2 via the seed crystal rod 5. The upper heat-preserving device 6, the middle heat-preserving device 7, the first heating device 71, the second heating device 61, the crucible 1, and the mold 2 are coaxially arranged.

[0044] As shown in Figure 2, the crystal 4 has a curved surface, and the second heating device 61 and the upper heat preservation device 6 are arc-shaped structures. As shown in Figure 3, the crucible 1, the mold 2, the middle heat preservation device 7, and the first heating device 71 are all arc-shaped structures.

[0045] Example 1:

[0046] This embodiment provides a method for growing curved crystals using a guided mold method, including: S1: placing the growth material into a crucible 1, placing a mold 2 inside the crucible 1, fixing a seed crystal 3 to one end of a seed crystal rod 5, the seed crystal rod 5 being connected to a lifting mechanism; positioning the seed crystal 3 3-50mm directly above the mold 2 via the seed crystal rod 5, the mold 2 having a curved inner cavity; the crucible 1 being located within a middle heat-insulating device 7, and the seed crystal 3 and part or all of the seed crystal rod 5 being located within an upper heat-insulating device 6; S2: evacuating the upper heat-insulating device 6 and the middle heat-insulating device 7, and then filling them with inert gas; S3: performing exhaust treatment; S4: raising the temperature inside the crucible 1 to a first temperature, and growing the growth material inside the crucible 1... S5: The seed crystal 3 is lowered to contact the upper surface of the mold 2 through the seed crystal rod 5, and the temperature inside the crucible 1 is raised to the second temperature again. Then the seed crystal 3 is pulled up through the seed crystal rod 5. S6: When the seed crystal is pulled up to a diameter reduction length of 7mm and the diameter reduction size is 1 / 2 of the original size of the seed crystal, the first cooling begins. The cooling is stopped when the width of the grown crystal is the same as the width of the mold, and the internal temperature of the mold is recorded as T1. S7: The crystal continues to grow. The temperature control after equal diameter is adjusted based on the temperature of T1 based on the data fed back by the sensor. After the crystal growth is completed, the temperature is T2. The whole crystal 4 is removed from the mold 2. S8: Annealing is performed after cooling.

[0047] By placing the growth material and seed crystal 3 into crucible 1 and placing mold 2 inside crucible 1, a uniform heating space is provided for the growth of crystal 4, controlling the release of growth stress and thermal stress in crystal 4. This prevents crystal 4 from cracking after cooling or from cracking due to excessive stress during processing, and avoids deformation of crystal 4 due to uneven heating during growth. This results in a high surface flatness of the finished crystal 4, reducing the amount of grinding and polishing required. Vacuuming the upper insulation device 6 and the middle insulation device 7 and filling them with inert gas effectively suppresses the oxidation and volatilization of the heater and insulation material after heating, preventing oxidation and volatilization from contaminating the growth material. Exhausting the gas removes impurities released from the internal components of the insulation devices, thereby improving the quality of crystal 4. After the material is melted, the seed crystal... 3. The curved cavity of the contact mold 2 is used to grow curved crystal 4, avoiding complex cutting and roughing techniques and reducing cost waste. By controlling the first temperature, the second temperature, and the internal temperature T1 and T2 of the mold 2 through the curved inner cavity of the mold 2, and with a reasonable lifting speed, the microbubbles in the crystal 4 are controlled to be a small part of the surface of the crystal 4. This improves the growth quality of the crystal 4 and the surface smoothness of the finished crystal 4. It avoids the need for constant diameter growth when the crystal 4 is placed to the same width as the mold 2. After the constant diameter growth is completed, the crystal 4 is separated from the mold 2 and then annealed. This can produce curved crystal 4 with a short growth cycle. Curved crystal 4 that can meet the requirements of direct grinding and polishing can be grown directly, which greatly reduces the cost of cutting and roughing in the early stage.

[0048] The angle between the V-shaped opening on the upper surface of the growth material and the upper surface of mold 2 is 140°, and the distance between the lower surface of mold 2 and the bottom surface of crucible 1 is 25mm. The 140° angle of the V-shaped opening on the upper surface of mold 2 prevents the temperature of the middle crystal 4 from being lower than that of the crystals growing on the sides, ensuring that crystal 4 grows under uniform heating. The growth material enters the interior of mold 2 through the gap between the lower surface of mold 2 and the bottom surface of crucible 1, and is transported to the upper surface of mold 2 via capillary action.

[0049] The crucible 1 and the first heating device 71 are disposed inside the cavity of the middle heat preservation device 7. The first heating device 71 is disposed outside the crucible 1, and the second heating device 61 is disposed inside the cavity of the upper heat preservation device 6. The crucible 1, the first heating device 71, the second heating device 61, the middle heat preservation device 7, and the upper heat preservation device 6 have an arc-shaped structure. The inner surface of the cavity of the crucible 1, the inner surface of the cavity of the first heating device 71, the inner surface of the cavity of the second heating device 61, the inner surface of the cavity of the middle heat preservation device 7, and the inner surface of the cavity of the upper heat preservation device 6 are all arc surfaces. A lower heat preservation device 8 is connected below the middle heat preservation device 7. A power supply device 81 is disposed inside the lower heat preservation device 8. The first heating device 71 and the second heating device 61 are both electrically connected to the power supply device 81. By making the crucible 1, the first heating device 71, the second heating device 61, the middle heat preservation device 7, and the upper heat preservation device 6 into arc-shaped structures, and making the interior of the cavity an arc surface, the temperature field where the curved crystal 4 is located can meet the growth requirements of the crystal 4. This can avoid the failure of crystal 4 growth due to local overcooling caused by uneven temperature of the crystal 4, realize the rapid heat transport direction and heat transport control during the growth of the crystal 4, grow high-quality crystals with shallow bubble layers and smooth surfaces, reduce the amount of grinding and polishing required for the finished crystal 4, and achieve the growth of curved sapphire crystal 4.

[0050] In S1, the growth material is alumina. In S2, a vacuum is drawn to below 6 Pa, and the inert gases are argon and nitrogen; the flow rate of the inert gases is 2.5 L / min. By filling with argon and nitrogen at a pressure below 6 Pa, the oxidation and volatilization of the heater and insulation material after heating are effectively suppressed, avoiding contamination of the growth material by oxidation and volatilization.

[0051] The exhaust process in S3 is as follows: exhaust is carried out in the upper insulation device 6 and the lower insulation device 8. When the air pressure is lower than 50 kPa, the exhaust is stopped.

[0052] In S4, the temperature inside the crucible 1 is heated to a first temperature by the first heating device 71. The heating time to the first temperature is 8 hours, the heating rate is 200℃ / h, the first temperature is 2100℃, and the temperature is kept constant at 2100℃ for 30 minutes. During S4, the temperature inside the upper heat preservation device 6 is controlled to be 1800℃ by the second heating device 61.

[0053] In S5, the second temperature is 80°C higher than the first temperature. After reaching the second temperature, it is held for 30 minutes, and then the seed crystal 3 is pulled up through the seed crystal rod 5 at a pulling speed of 50 mm / h. During S5, the temperature inside the upper holding device 6 is controlled at 1900°C by the second heating device 61. The temperature inside the crucible 1 is raised to the first temperature by the first heating device 71. The energy provided by the heater melts the alumina raw material in the crucible 1 into a melt. In S4, the temperature inside the upper holding device 6 is controlled at 1800°C by the second heating device 61, which can control the temperature of the seed crystal 3 in the holding device to be close to that of the crucible 1, while preventing the seed crystal 3 from melting. Then, it is raised by 80°C to reach the second temperature, so that the seed crystal 3 melts and forms a liquid film between itself and the melted growth raw material, thereby driving the growth of crystal 4. By pulling the seed crystal 3 to reduce its diameter, the risk of introducing defects from the seed crystal 3 into crystal 4 is reduced, thus improving the growth quality of crystal 4. During the S5 process, the temperature inside the upper heat preservation device 6 is controlled to be 1900℃ by the second heating device 61, so that the temperature of the seed crystal 3 is close to the growth temperature of the crystal 4, which is beneficial to the growth of the crystal 4 during the pulling process.

[0054] In step S6, the cooling rate is 25℃ / h; the internal temperature T1 of mold 2 is recorded; after crystal growth in step S7, the temperature is maintained at T2+10℃ for 15 minutes, then crystal 4 is lifted off mold 2 at a lifting speed of 1000mm / h, completing the growth of crystal 4. By reducing the diameter, crystal 4 is gradually sized to the same width as mold 2 for constant-diameter growth. After entering the constant-diameter stage, the growth rate of crystal 4 is determined by a weight sensor. Controlling the growth rate completes the crystal 4 growth process, which helps improve the quality of crystal 4.

[0055] After crystal 4 detaches from mold 2 in S8, the temperature of the middle heat preservation device 7 is cooled by stopping the heating of the first heating device 71 and the second heating device 61. The temperature of the middle heat preservation device 7 is reduced by 200°C from the temperature when crystal 4 detaches from mold 2. The temperature inside the upper heat preservation device 6 is cooled by stopping the heating of the first heating device 71 and the second heating device 61. The temperature inside the upper heat preservation device 6 is reduced by 170°C from the temperature when crystal 4 detaches from mold 2. After cooling and holding for 2.5 hours, annealing is completed. After annealing, the heating power of the first heating device 71 and the second heating device 61 is reduced, and the temperature is reduced at cooling rates of 259°C / h and 90°C / h, respectively. After being placed for 18 hours, it is taken out to obtain a curved sapphire crystal.

[0056] After being pulled out of mold 2, crystal 4 completes its growth and begins to cool down. After cooling, it is kept at a certain temperature for a period of time to allow crystal 4 to enter the annealing state, eliminating internal stress and growth defects in crystal 4. After cooling, crystal 4 is taken out, which can directly grow crystal 4 that can meet the requirements of direct grinding and polishing, greatly reducing material waste and effectively reducing costs.

[0057] Example 2:

[0058] The content that is the same as in Example 1 will not be repeated here; the differences between this embodiment and Example 1 are as follows:

[0059] This embodiment provides a guided mold method for growing curved crystals. The seed crystal 3 is positioned 4mm above the mold 2 via the seed crystal rod 5. S6: When the seed crystal is pulled up by a length of 6mm and the reduced diameter is 1 / 3 of the original size of the seed crystal, a cooling process is started.

[0060] The V-shaped opening on the upper surface of mold 2 has an angle of 95°. The distance between the lower surface of mold 2 and the bottom surface of crucible 1 is 0mm. A through hole connecting the crucible 1 and the interior of mold 2 is provided on the side of mold 2 at a position 0-20mm from the lower surface.

[0061] In S2, a vacuum is evacuated to below 2 Pa, with argon and nitrogen as the inert gases; the inert gas flow rate is 0.8 L / min. The pressure is then maintained below 2 Pa by introducing argon and nitrogen.

[0062] The exhaust process in S3 is as follows: exhaust is carried out in the upper insulation device 6 and the lower insulation device 8. When the air pressure is lower than 5 kPa, the exhaust is stopped.

[0063] In S4, the temperature inside the crucible 1 is heated to a first temperature by the first heating device 71. The heating time to the first temperature is 5 hours, the heating rate is 90℃ / h, the first temperature is 2070℃, and it is kept at 2100℃ for 5 minutes. During S4, the temperature inside the upper heat preservation device 6 is controlled to be 1770℃ by the second heating device 61.

[0064] In S5, the second temperature is 30°C higher than the first temperature. After reaching the second temperature, the temperature is maintained for 7 minutes, and then the seed crystal 3 is pulled up by the seed crystal rod 5 at a pulling speed of 10 mm / h. During S5, the temperature inside the upper heat preservation device 6 is controlled to be 1950°C by the second heating device 61.

[0065] The first heating device 71 raises the temperature inside the crucible 1 to a first temperature. The energy provided by the heater melts the alumina raw material inside the crucible 1 into a melt. In process S4, the second heating device 61 controls the temperature inside the upper heat preservation device 6 to 1770℃, ensuring that the temperature of the seed crystal 3 in the upper heat preservation device 6 is close to that of the crucible 1, while preventing the seed crystal 3 from melting. By raising the temperature by 30℃ to a second temperature, a liquid film is formed between the melted seed crystal 3 and the melted growth material, thereby driving the growth of crystal 4. By pulling the seed crystal 3 to reduce its diameter, the risk of defects in the seed crystal 3 being introduced into crystal 4 is reduced, improving the growth quality of crystal 4. In process S5, the second heating device controls the temperature inside the upper heat preservation device to 1950℃, making the seed crystal temperature close to the crystal growth temperature, which is beneficial for crystal growth during the pulling process.

[0066] In S6, the cooling rate for one cooling cycle is 5℃ / h; the internal temperature T1 of mold 2 is recorded; after crystal growth is completed in S7, the temperature is kept at T2+10℃ for 12 minutes, and then crystal 4 is removed from mold 2 at a pulling speed of 950mm / h.

[0067] The temperature of the middle heat preservation device 7 is reduced by 185°C from the temperature when the crystal 4 is removed from the mold 2; the temperature inside the upper heat preservation device 6 is reduced by 165°C from the temperature when the crystal 4 is removed from the mold 2; after cooling and heat preservation for 1.5 hours, annealing is completed; after annealing, the heating power of the first heating device 71 and the second heating device 61 is reduced to a cooling rate of 110°C / h and 90°C / h respectively, and then the crystal is placed for 12 hours before being taken out to obtain a curved sapphire crystal.

[0068] Example 3:

[0069] The content that is the same as in Example 2 will not be repeated here; the differences between this embodiment and Example 2 are as follows:

[0070] This embodiment provides a guided mold method for growing curved crystals. The seed crystal 3 is positioned 45mm above the mold 2 via the seed crystal rod 5. S6: When the seed crystal is pulled up by a length of 9mm and the reduced diameter is half of the original size of the seed crystal, a cooling process is started.

[0071] The V-shaped opening on the upper surface of mold 2 has an angle of 175°, and the distance between the lower surface of mold 2 and the bottom surface of crucible 1 is 40mm.

[0072] In S2, a vacuum is evacuated to below 8 Pa, with argon and nitrogen as the inert gases; the flow rate of the inert gases is 4 L / min. The pressure is then maintained below 8 Pa by introducing argon and nitrogen.

[0073] The exhaust process in S3 is as follows: exhaust is carried out in the upper insulation device 6 and the lower insulation device 8. When the air pressure is lower than 95 kPa, the exhaust is stopped.

[0074] In S4, the temperature inside the crucible 1 is heated to a first temperature by the first heating device 71. The heating time to the first temperature is 8 hours, the heating rate is 280℃ / h, the first temperature is 2100℃, and the temperature is kept constant at 2100℃ for 28 minutes. During S4, the temperature inside the upper heat preservation device 6 is controlled to be 1890℃ by the second heating device 61.

[0075] In S5, the second temperature is 140°C higher than the first temperature. After reaching the second temperature, the temperature is maintained for 55 minutes, and then the seed crystal 3 is pulled up through the seed crystal rod 5 at a pulling speed of 95 mm / h. During S5, the temperature inside the upper heat preservation device 6 is controlled to be 1990°C through the second heating device 61.

[0076] The first heating device 71 raises the temperature inside the crucible 1 to a first temperature. The energy provided by the heater melts the alumina raw material inside the crucible 1 into a melt. In process S4, the second heating device 61 controls the temperature inside the upper heat-preserving device 6 to 1890°C, ensuring that the temperature of the seed crystal 3 in the upper heat-preserving device 6 is close to that of the crucible 1, while preventing the seed crystal 3 from melting. By raising the temperature by 140°C to a second temperature, a liquid film is formed between the melted seed crystal 3 and the melted growth material, thereby driving the growth of crystal 4. By pulling the seed crystal 3 to reduce its diameter, the risk of introducing defects from the seed crystal 3 into crystal 4 is reduced, improving the growth quality of crystal 4. In process S5, the second heating device controls the temperature inside the upper heat-preserving device to 1990°C, making the seed crystal temperature close to the crystal growth temperature, which is beneficial for crystal growth during the pulling process.

[0077] In S6, the cooling rate during the first cooling step is 45℃ / h; the internal temperature T1 of mold 2 is recorded; after crystal growth is completed in S7, the temperature is kept at T2+10℃ for 18 minutes, and then crystal 4 is removed from mold 2 at a pulling speed of 1050mm / h.

[0078] The temperature of the middle heat preservation device 7 is reduced by 210°C from the temperature when the crystal 4 is removed from the mold 2; the temperature inside the upper heat preservation device 6 is reduced by 170°C from the temperature when the crystal 4 is removed from the mold 2; after cooling and heat preservation for 3 hours, annealing is completed; after annealing, the heating power of the first heating device 71 and the second heating device 61 is reduced, and the temperature is reduced at cooling rates of 350°C / h and 90°C / h respectively. After being placed for 23 hours, the crystal is taken out to obtain a curved sapphire crystal.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. 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; and these 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.

Claims

1. A method for growing curved surface crystals using the guided model method, characterized in that: S1: Place the growth material into the crucible (1), place the mold (2) into the crucible (1), fix the seed crystal (3) at one end of the seed crystal rod (5), the seed crystal rod (5) is connected to the lifting mechanism; place the seed crystal (3) through the seed crystal rod (5) at a position 3-50mm directly above the mold (2), the mold (2) is provided with a curved inner cavity; The crucible (1) is located inside the central heat preservation device (7); S2: Evacuate the upper insulation device (6) and the middle insulation device (7) and then fill them with inert gas; S3: Perform exhaust treatment; S4: Raise the temperature inside the crucible (1) to the first temperature to melt the growth material inside the crucible (1); S5: After the seed crystal (3) is lowered to contact the upper surface of the mold (2) by the seed crystal rod (5), the temperature inside the crucible (1) is raised to the second temperature again, and then the seed crystal (3) is pulled up by the seed crystal rod (5); S6: When the diameter of the seed crystal (3) is reduced and the length is pulled up by 5-10mm, and the diameter of the seed crystal (3) is 1 / 3 to 1 / 2 of the original size of the seed crystal (3), start the first cooling, so that the width of the grown crystal (4) is the same as the width of the mold (2), stop the cooling, and record the internal temperature T1 of the mold (2). S7: The crystal continues to grow. The temperature control after the constant diameter is adjusted based on the temperature of T1 by the data fed back by the sensor. After the crystal growth is completed, the temperature is T2. The whole crystal (4) is removed from the mold (2). S8: Annealing is performed after cooling.

2. The method for growing curved crystals using the guided-mode method according to claim 1, characterized in that: The crucible (1) and the first heating device (71) are disposed in the cavity of the middle heat preservation device (7), and the first heating device (71) is disposed outside the crucible (1); the second heating device (61) is disposed in the cavity of the upper heat preservation device (6); The crucible (1), the first heating device (71), the second heating device (61), the middle heat preservation device (7) and the upper heat preservation device (6) are all arc-shaped structures; The inner surface of the cavity of the crucible (1), the inner surface of the cavity of the first heating device (71), the inner surface of the cavity of the second heating device (61), the inner surface of the cavity of the middle heat preservation device (7) and the inner surface of the cavity of the upper heat preservation device (6) are all arc surfaces. The lower insulation device (8) is connected below the middle insulation device (7), and the lower insulation device (8) is equipped with a power supply device (81). The first heating device (71) and the second heating device (61) are both electrically connected to the power supply device (81). The upper surface of the mold (2) has a V-shaped opening with an angle of 90°-180°. The distance between the lower surface of the mold (2) and the bottom surface of the crucible (1) is 0-50mm. When the distance between the lower surface of the mold (2) and the bottom surface of the crucible (1) is 0mm, a through hole connecting the crucible (1) and the interior of the mold (2) is provided on the side of the mold (2) at a position 0-20mm away from the lower surface.

3. The method for growing curved crystals using the guided-mode method according to claim 1, characterized in that: The growth material in S1 is alumina.

4. The method for growing curved crystals using the guided-mode method according to claim 1, characterized in that: In step S2, the vacuum is evacuated to below 10 Pa, and the inert gas is argon or nitrogen; the flow rate of the inert gas is 0.5-5 L / min.

5. The method for growing curved crystals using the guided-mode method according to claim 1, characterized in that: The exhaust gas treatment process in S3 is as follows: Exhaust gas into the upper insulation device (6) and the lower insulation device (8). When the gas pressure is lower than 1 kPa-100 kPa, stop exhausting gas.

6. The method for growing curved crystals using the guided-mode method according to claim 1, characterized in that: In S4, the temperature inside the crucible (1) is raised to a first temperature by the first heating device (71). The heating time to the first temperature is 4-10h, the heating rate is 80-300℃ / h, the first temperature is 2050-2200℃, and the temperature is kept constant at 2050-2200℃ for 5-35min. During the S4 process, the temperature inside the upper heat preservation device (6) is controlled to be 1750-1900℃ by the second heating device (61).

7. The method for growing curved crystals using the guided-mode method according to claim 1, characterized in that: In S5, the second temperature is 20-150°C higher than the first temperature. After reaching the second temperature, the temperature is maintained for 5-60 minutes, and then the seed crystal (3) is pulled up through the seed crystal rod (5). The pulling speed is 5-100 mm / h. During the S5 process, the temperature inside the upper heat preservation device (6) is controlled to be 1800-2000℃ by the second heating device (61).

8. The method for growing curved crystals using the guided-mode method according to claim 1, characterized in that: The cooling rate of one cooling cycle in S6 is 1-50℃ / h; record the internal temperature T1 of the mold (2).

9. The method for growing curved crystals using the guided-mode method according to claim 1, characterized in that: After the crystal (4) in S7 is finished, wait for 10-20 minutes at T2+10℃, and then pull the crystal (4) out of the mold (2) at a pulling speed of 900-1100mm / h through the seed crystal rod (5) at the internal temperature of T2+10℃.

10. The method for growing curved crystals using the guided-mode method according to claim 1, characterized in that: After the crystal (4) in S8 is removed from the mold (2), the temperature of the heat preservation device (7) is reduced by stopping the heating through the first heating device (71) and the second heating device (61). The temperature of the heat preservation device (7) is reduced by 180-220°C from the temperature when the crystal (4) is removed from the mold (2). The temperature inside the upper heat preservation device (6) is cooled down by stopping the heating through the first heating device (71) and the second heating device (61). The temperature inside the upper heat preservation device (6) is reduced by 160-180°C from the temperature when the crystal (4) leaves the mold (2). After cooling and holding for 1-4 hours, annealing is completed. After annealing, the heating power of the first heating device (71) and the second heating device (61) is reduced, and the temperature is reduced at a rate of 100-400℃ / h and 80-100℃ / h, respectively. Then, the product is placed for 10-24 hours before being taken out.

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