Edge-defined film-fed crystal growth method

Abstract

The invention discloses an edge-defined film-fed crystal growth method, which comprises: S1, placing a growth raw material in a crucible, placing a mold in the crucible, placing a seed crystal at a position 3-50 mm right above the mold through a seed crystal rod, the mold being provided with a curved surface inner cavity; s2, the upper heat preservation device and the middle heat preservation device are vacuumized and filled with inert gas; s3, performing exhaust treatment; s4, raising the temperature in the crucible to a first temperature, and melting the growth raw material in the crucible; s5, the seed crystal makes contact with the mold, the temperature is increased to a second temperature, and the seed crystal is pulled up; s6, reducing the diameter of the seed crystal, pulling the seed crystal for 5-10 mm, and cooling for the first time; s7, separating the crystal from the mold; and S8, annealing treatment is conducted after cooling. A uniform heating space is provided for growth of crystals, release of growth stress and thermal stress of the crystals is controlled, and impurities volatilized in the process of taking away the interior of the heat preservation device at high temperature are taken away through exhaust; the seed crystal is in contact with the curved-surface inner cavity of the mold to grow the curved-surface crystal, so that the cutting and rough machining cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of crystal growth, in particular to a guided-mode curved-surface crystal growth method. Background Art

[0002] Sapphire is a single crystal of aluminum oxide, a material with excellent physical, chemical and optical properties. Sapphire is used as LED and SOS substrates due to its unique optical and physical properties, lattice matching and good thermal properties. It is used as front laser, gravitational wave interferometer, transparent armor, infrared window material and other industrial, civilian and wearable consumer electronic products due to its high thermal conductivity, high melting point and high mechanical strength.

[0003] There are three methods for growing sapphire crystals: KY method (Kyropoulos method), Cz method (Czochralski method), EFG method (guided mold method), and HEM method (heat exchange method). The traditional guided mold method basically grows flat crystals. Since the thickness of the grown flat crystals is thin, basically within 20mm, it is difficult to process curved sapphire crystals.

[0004] Sapphire ingots grown by the Kyropoulos method can meet the requirements for processing curved sapphire, but face complex cutting and rough processing technology and costs. However, large-sized curved sapphire crystal ingots prepared by the Kyropoulos method cannot meet the material extraction conditions.

[0005] Therefore, processing curved sapphire crystals and greatly reducing the initial cutting and rough processing costs and risks are issues that need to be addressed. Summary of the invention

[0006] In view of the above problems, the present invention designs a method for growing curved crystals by a guided mold method, comprising S1: placing a growth raw material into a crucible, placing a mold in the crucible, fixing a seed crystal at one end of a seed crystal rod, wherein the seed crystal rod is connected to a lifting mechanism; placing the seed crystal 3-50 mm above the mold through the seed crystal rod, wherein the mold is provided with a curved inner cavity;

[0007] The crucible is located in the middle heat preservation device, and the seed crystal and part or all of the seed crystal rod are located in the upper heat preservation device;

[0008] S2: evacuate the upper insulation device and the middle insulation device, and then fill them with inert gas;

[0009] S3: perform exhaust treatment;

[0010] S4: raising the temperature in the crucible to a first temperature to melt the growth raw material in the crucible;

[0011] S5: After the seed crystal is lowered to contact the upper surface of the mold by the seed crystal rod, the temperature in the crucible is raised to a second temperature again, and then the seed crystal is pulled up by the seed crystal rod;

[0012] S6: When the seed crystal is pulled down to a length of 5-10 mm and the seed crystal neck size is 1 / 3 to 1 / 2 of the original size of the seed crystal, the temperature is lowered once until the width of the growing crystal is the same as the width of the mold, and the temperature inside the mold is recorded.

[0013] S7: The crystal continues to grow, and the temperature control after equal diameter is adjusted based on the temperature of T1 through the data fed back by the sensor. After the crystal growth is completed, the temperature is T2, and the whole crystal is separated from the mold;

[0014] S8: After cooling, annealing is performed.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: by placing the growth raw materials and seed crystals 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 release of the crystal are controlled, the cracking of the crystal after cooling or the cracking due to excessive stress during the processing is avoided, the deformation of the crystal during the growth process due to uneven heating of the crystal is avoided, the surface flatness of the finished crystal is high, and the grinding and polishing amount of the finished crystal is reduced; the upper insulation device and the middle insulation device are evacuated and filled with inert gas, which effectively inhibits the oxidation volatilization of the crystal after heating, avoids the oxidation volatilization from polluting the growth raw materials, and the impurities released by the internal related accessories of the insulation device can be taken away by exhaust, thereby improving the quality of the crystal; in the process of chemical material Then, the seed crystal contacts the curved cavity of the mold, thereby growing a curved crystal, avoiding complicated cutting and rough processing technologies, reducing cost waste, and providing a curved inner cavity in the mold to control the first temperature, the second temperature, and the internal temperatures T1 and T2 of the mold, in combination with a reasonable pulling speed, to control the microbubbles in the crystal to a very small part of the crystal surface; improving the growth quality of the crystal, improving the surface smoothness of the finished crystal, avoiding equal-diameter growth when the crystal is shouldered to the same width as the mold, and after the equal-diameter growth is completed, separating the crystal from the mold, and then performing annealing to obtain a curved sapphire crystal with a short growth cycle, directly growing a curved crystal that can meet direct grinding and polishing processing, and greatly reducing the initial cutting and rough processing costs.

[0016] Further, the angle between the upper surface of the growth material and the upper surface of the mold is 90°-180°, the distance between the lower surface of the mold and the bottom of the crucible is 0-50 mm, and when the distance between the lower surface of the mold and the bottom of the crucible is 0 mm, the lower surface of the mold is provided with a through hole connecting the crucible and the inside of the mold;

[0017] The beneficial effect of adopting the above-mentioned further technical scheme is: by setting the angle between the upper surface of the growing raw material and the upper surface of the mold to 90°-180°, it is possible to avoid the temperature of the middle growing crystal being lower than the temperature of the growing crystals on both sides, so that the crystals grow under uniform heating conditions, and the growing raw 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.

[0018] Further, the crucible and the first heating device are arranged in the cavity of the middle heat preservation device, the first heating device is arranged outside the crucible, and the second heating device is arranged in the cavity of the upper heat preservation device;

[0019] The crucible, the first heating device, the second heating device, the middle insulation device and the upper insulation device are arc-shaped structures, and the inner surface of the cavity of the crucible, the inner surface of the cavity of the first heating device, the inner surface of the cavity of the second heating device, the inner surface of the cavity of the middle insulation device and the inner surface of the cavity of the upper insulation device are all arc surfaces;

[0020] Preferably, a lower heat insulation device is connected below the middle heat insulation device, a power supply device is arranged in the lower heat insulation device, and the first heating device and the second heating device are both electrically connected to the power supply device.

[0021] The beneficial effect of adopting the above-mentioned further technical scheme is as follows: by making the crucible, the first heating device, the second heating device, the middle insulation device and the upper insulation device into an arc structure, and the interior of the cavity into an arc surface, the temperature field where the curved surface crystal is located can meet the needs of crystal growth, and it can avoid that the uneven crystal temperature causes local overcooling and causes the crystal growth failure, and realize the rapid heat transfer direction and heat transfer control in crystal growth, grow high-quality, bubble layer, smooth surface, reduce the amount of grinding and polishing of the finished crystal, and achieve the growth of curved surface sapphire crystal.

[0022] Furthermore, the growth raw material in S1 is an aluminum oxide raw material.

[0023] Furthermore, the S2 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.

[0024] The beneficial effect of adopting the above further technical solution is: by filling argon and nitrogen below 10Pa, the oxidation volatilization of the crystal after heating is effectively suppressed, avoiding the pollution of the growth raw materials by oxidation volatilization.

[0025] Furthermore, the exhaust treatment process in S3 is:

[0026] The temperature in the crucible is heated to 2050-2200°C by the first heating device, and the constant temperature is 2050-2200°C, which is maintained for 25-35 minutes, and then the upper insulation device and the lower insulation device are evacuated. When the gas pressure is lower than 1kpa-100kpa, the evacuation is stopped.

[0027] The beneficial effect of adopting the above further technical solution is that the impurities released from the internal related accessories of the heat preservation device are taken away by exhaust gas at high temperature, thereby improving the quality of the crystal.

[0028] Furthermore, the heating time to the first temperature in S4 is 4-10 hours, the heating rate is 80-300°C / h, and the first temperature is 2050-2200°C;

[0029] During S4, the temperature in the upper insulation device is controlled to be 1750°C-1900°C by the second heating device.

[0030] Furthermore, in S5, the second temperature is 20-150° C. higher than the first temperature, and after reaching the second temperature, the temperature is kept for 5-60 minutes, and then the seed crystal is pulled up by the seed crystal rod, and the pulling speed is 5-100 mm / h;

[0031] In the S5 process, the temperature in the upper insulation device is controlled to be 1800° C.-2000° C. by the second heating device.

[0032] The beneficial effects of adopting the above-mentioned further technical scheme are as follows: when the temperature reaches the first temperature, thermal convection melts the alumina raw material in the crucible into a melt, and the temperature in the upper insulation device is controlled to be 1750℃-1900℃ by the second heating device, so that the temperature of the seed crystal in the insulation device can be controlled to be close to that of the crucible, while avoiding the melting of the seed crystal; by increasing 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 the growth of the crystal, and by pulling up the seed crystal, the crystal is pulled to shrink the diameter, and the bubbles in the crystal are initially released, thereby avoiding the phenomenon of bubbling of the finished crystal, improving the growth quality of the crystal, and improving the surface smoothness of the finished crystal; by controlling the temperature in the upper insulation device to be 1800℃-2000℃ by the second heating device, the temperature of the seed crystal is close to the crystal growth temperature, which is beneficial to the growth of the crystal during the pulling process.

[0033] Furthermore, the cooling rate of the first cooling in S6 is 1-50°C / h; the internal temperature T1 of the mold is recorded;

[0034] After the crystal growth is completed in S7, the temperature is kept at T2+10° C. for 10-20 minutes, and then the whole crystal is separated from the mold.

[0035] The beneficial effects of adopting the above-mentioned further technical scheme are: by reducing the diameter, the crystal is slowly shouldered to the same width as the mold and then grows in equal diameter. After entering the equal diameter stage, the growth rate of the crystal is judged by a weight sensor, and the crystal growth process is completed by controlling the growth rate, which is beneficial to the perfect development of the crystal; at the internal temperature of the mold T2+10℃ and the pulling speed of 900-1100mm / h, the crystal is separated from the mold to complete the crystal growth.

[0036] Further, in S8, after the crystal is separated from the mold, the temperature of the middle heat preservation device is cooled by the first heating device and the second heating device, and the temperature of the middle heat preservation device is cooled by 180-220° C. based on the temperature when the crystal is separated from the mold;

[0037] The temperature in the upper heat preservation device is lowered by the first heating device and the second heating device, and the temperature in the upper heat preservation device is lowered by 160-180° C. based on the temperature when the crystal is separated from the mold;

[0038] After cooling, the material is kept warm for 1-4 hours to complete annealing. After annealing, the material is cooled by the first heating device and the second heating device at a cooling rate of 100-400°C / h and 80-100°C / h respectively, and then placed for 10-24 hours before being taken out.

[0039] The beneficial effects of adopting the above-mentioned further technical scheme are as follows: after being pulled out of the mold, the crystal growth is completed and the temperature begins to drop. After cooling down, the crystal is kept warm for a period of time so that the crystal enters the annealing state, which can refine the grains, eliminate the internal stress and processing defects of the crystal, and reduce the hardness. After cooling, the crystal is taken out and a crystal that can meet the direct grinding and polishing processing can be directly grown, which greatly reduces the waste of materials and effectively reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is the cross-sectional view of the curved surface temperature field and the curved surface mold;

[0041] Figure 2 is a top view of the upper insulation device;

[0042] Figure 3 It is a top view of the middle insulation device;

[0043] Among them: 1. crucible; 2. mold; 3. seed crystal; 4. crystal; 5. seed crystal rod; 6. upper insulation device; 61. second heating device; 7. middle insulation device; 71. first heating device; 8. lower insulation device; 81. power supply device. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clear, 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.

[0045] Embodiment 1:

[0046] The present embodiment provides a method for growing curved crystals using a guided mold method, comprising: S1: placing a growth raw material into a crucible 1, placing a mold 2 in the crucible 1, fixing a seed crystal 3 at one end of a seed crystal rod 5, wherein the seed crystal rod 5 is connected to a lifting mechanism; placing the seed crystal 3 at a position 3-50 mm above the mold 2 through the seed crystal rod 5, wherein the mold 2 is provided with a curved inner cavity; the crucible 1 is located in a middle heat preservation device 7, and the seed crystal 3 and part or all of the seed crystal rod 5 are located in an upper heat preservation device 6; S2: evacuating the upper heat preservation device 6 and the middle heat preservation device 7, and then filling them with an inert gas; S3: performing exhaust treatment; S4: raising the temperature in the crucible 1 to a first temperature, and then placing the crucible 1 in the middle heat preservation device 7; The internal growth raw material is melted; S5: after the seed crystal 3 is lowered to contact with the upper surface of the mold 2 through the seed crystal rod 5, the temperature in 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 seed crystal is pulled to a length of 7mm and the seed crystal neck size is 1 / 2 of the original size of the seed crystal, a cooling process is started to make the width of the growing crystal the same as the width of the mold, and the cooling is stopped, and the temperature T1 inside the mold is recorded; S7: the crystal continues to grow, and the temperature control after equal diameter is adjusted based on the temperature T1 through the data fed back by the sensor. After the crystal growth is completed, the temperature is T2, and the whole crystal 4 is separated from the mold 2; S8: annealing treatment is carried out after cooling. By placing the growth raw materials and seed crystal 3 into the crucible 1, and placing the mold 2 in the crucible 1, a uniform heating space is provided for the growth of the crystal 4, and the growth stress and thermal stress release of the crystal 4 are controlled, so as to avoid the cracking of the crystal 4 after cooling down or the cracking caused by excessive stress during the processing process, and to avoid the deformation of the crystal 4 during the growth process due to uneven heating of the crystal 4, so that the surface flatness of the finished crystal 4 is high, and the grinding and polishing amount of the finished crystal 4 is reduced; the upper insulation device 6 and the middle insulation device 7 are evacuated and filled with inert gas, which effectively inhibits the oxidation volatilization of the crystal 4 after heating, and avoids the oxidation volatilization from polluting the growth raw materials. The impurities released by the internal related accessories of the insulation device can be taken away by exhaust, thereby improving the quality of the crystal 4; after the material is oxidized, the seed crystal 3 contacts the The curved cavity of the mold 2 is used to grow a curved crystal 4, thereby avoiding complicated cutting and rough processing technologies and reducing cost waste. The mold 2 is provided with a curved inner cavity, and the first temperature, the second temperature, and the internal temperatures T1 and T2 of the mold 2 are controlled, and a reasonable pulling speed is used to control the microbubbles in the crystal 4 to a very small part of the surface of the crystal 4; the growth quality of the crystal 4 is improved, and the surface smoothness of the finished crystal 4 is improved, and when the crystal 4 is shouldered to the same width as the mold 2, equal-diameter growth is avoided. After the equal-diameter growth is completed, the crystal 4 is separated from the mold 2, and then annealing is performed to obtain a curved crystal 4 with a short growth cycle, and a curved crystal 4 that can meet direct grinding and polishing processing can be directly grown, which greatly reduces the initial cutting and rough processing costs.

[0047] Furthermore, the angle between the upper surface of the growth material and the upper surface of the mold 2 is 140°, and the distance between the lower surface of the mold 2 and the bottom surface of the crucible 1 is 25 mm;

[0048] By setting the angle between the upper surface of the growing raw material and the upper surface of the mold 2 to 140°, it is possible to avoid the temperature of the middle growing crystal 4 being lower than the temperature of the growing crystals 4 on both sides, so that the crystal 4 can grow under uniform heating conditions. The growing raw material enters the interior of the mold 2 through the gap between the lower surface of the mold 2 and the bottom surface of the crucible 1, and is transported to the upper surface of the mold 2 by capillary action.

[0049] The crucible 1 and the first heating device 71 are arranged in the cavity of the middle insulation device 7, the first heating device 71 is arranged outside the crucible 1, and the second heating device 61 is arranged in the cavity of the upper insulation device 6; the crucible 1, the first heating device 71, the second heating device 61, the middle insulation device 7 and the upper insulation device 6 are arc-shaped structures, and 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 insulation device 7 and the inner surface of the cavity of the upper insulation device 6 are all arc surfaces; preferably, a lower insulation device 8 is connected to the lower middle insulation device 7, a power supply device 81 is arranged in the lower insulation device 8, and 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 insulation device 7 and the upper insulation device 6 into an arc structure, and the interior of the cavity into an arc surface, the temperature field where the curved crystal 4 is located can meet the growth requirements of the crystal 4, and can avoid the uneven temperature of the crystal 4 causing local overcooling and the failure of the crystal 4 growth, and realize the rapid heat transfer direction and heat transfer control in the growth of the crystal 4, grow high-quality, bubble layer hidden, smooth surface, reduce the grinding and polishing amount of the finished crystal 4, and achieve the growth of curved sapphire crystal 4.

[0050] The growth raw material in S1 is aluminum oxide raw material. S2 is evacuated to below 6 Pa, and the inert gas is argon and nitrogen; the flow rate of the inert gas is 2.5 L / min. By filling argon and nitrogen below 6 Pa, the oxidation volatilization of the crystal 4 after heating is effectively suppressed, avoiding oxidation volatilization from contaminating the growth raw material.

[0051] The exhaust treatment process in S3 is: the temperature in the crucible is heated to 2100°C by the first heating device, the temperature is kept constant at 2100°C, and the temperature is kept constant for 30 minutes, and then the upper insulation device 6 and the lower insulation device 8 are evacuated, and the evacuation is stopped when the air pressure is lower than 50 kPa. The exhaust treatment removes impurities released by the internal related accessories of the insulation device at high temperature, thereby improving the quality of the crystal 4.

[0052] The heating time to the first temperature in S4 is 8 hours, the heating rate is 200°C / h, and the first temperature is 2100°C. During S4, the temperature in the upper insulation device 6 is controlled to be 1800°C by the second heating device 61.

[0053] The second temperature in S5 is 20-150°C higher than the first temperature. After reaching the second temperature, the temperature is kept for 30 minutes and then the seed crystal 3 is pulled up by the seed crystal rod 5. The pulling speed is 50mm / h. During S5, the temperature in the upper insulation device 6 is controlled to be 1900°C by the second heating device 61. When the temperature reaches the first temperature, thermal convection melts the alumina raw material in the crucible 1 into a melt, and the temperature in the upper insulation device 6 is controlled to be 1800°C by the second heating device 61, so that the temperature of the seed crystal 3 in the insulation device can be controlled to be close to that of the crucible 1, and the seed crystal 3 can be prevented from melting; by increasing the temperature by 80°C to reach the second temperature, a liquid film is formed between the melted seed crystal 3 and the melted growth raw material, thereby driving the growth of the crystal 4, and by pulling up the seed crystal 3, the crystal 4 is pulled to shrink the diameter, and the bubbles in the crystal 4 are initially released, thereby avoiding the phenomenon of bubbling of the finished crystal 4, improving the growth quality of the crystal 4, and improving the surface smoothness of the finished crystal 4; by controlling the temperature in the upper insulation device 6 to be 1900°C by the second heating device 61, 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] The cooling rate of the first cooling in S6 is 25℃ / h; the internal temperature T1 of the mold 2 is recorded; after the crystal growth is completed in S7, the temperature is kept at T2+10℃ for 15 minutes, and then the whole crystal is separated from the mold. Through diameter reduction, the crystal 4 is slowly placed on the same width as the mold 2 and then grows in equal diameter. After entering the equal diameter stage, the growth rate of the crystal 4 is determined by the weight sensor, and the growth process of the crystal 4 is completed by controlling the growth rate, which is conducive to the perfect development of the crystal 4; the crystal 4 is separated from the mold 2 at a pulling speed of 1000mm / h at the internal temperature of the mold 2 T2+10℃, and the growth of the crystal 4 is completed.

[0055] In the above S8, after the crystal 4 is separated from the mold 2, the temperature of the middle heat preservation device 7 is cooled by the first heating device 71 and the second heating device 61, and the temperature of the middle heat preservation device 7 is cooled by 200°C based on the temperature when the crystal 4 is separated from the mold 2; the temperature in the upper heat preservation device 6 is cooled by the first heating device 71 and the second heating device 61, and the temperature in the upper heat preservation device 6 is cooled by 170°C based on the temperature when the crystal 4 is separated from the mold 2; after cooling, the temperature is kept for 2.5 hours to complete the annealing; after the annealing treatment, the temperature is cooled by the first heating device 71 and the second heating device 61 at a cooling rate of 259°C / h and 90°C / h respectively, and then placed for 18 hours before being taken out. After being pulled out of the mold 2, the crystal 4 is grown and starts to cool down. After cooling, it is kept for a period of time to make the crystal 4 enter the annealing state, which can refine the grains, eliminate the internal stress and processing defects of the crystal 4, reduce the hardness, and take out the crystal 4 after cooling, so that the crystal 4 that can meet the direct grinding and polishing processing can be directly grown, which greatly reduces the waste of materials and effectively reduces the cost.

[0056] Embodiment 2:

[0057] The same contents as those in the first embodiment are not described in detail here. The differences between the first embodiment and the present embodiment are as follows:

[0058] This embodiment provides a method for growing curved crystals using a guided mold method, wherein a seed crystal 3 is placed 4 mm above a mold 2 through a seed crystal rod 5; S6: when the seed crystal is pulled to a length of 6 mm and the seed crystal necking size is 1 / 3 of the original size of the seed crystal, a cooling process is started;

[0059] Further, the angle between the upper surface of the growth material and the upper surface of the mold 2 is 95°, and the distance between the lower surface of the mold 2 and the bottom surface of the crucible 1 is 0 mm. When the distance between the lower surface of the mold 2 and the bottom of the crucible 1 is 0 mm, the lower surface of the mold 2 is provided with a through hole connecting the crucible 1 and the inside of the mold 2;

[0060] The angle between the upper surface of the growing material and the upper surface of the mold 2 is 95°.

[0061] The S2 is evacuated to below 2 Pa, the inert gas is argon or nitrogen, and the flow rate of the inert gas is 0.8 L / min. Argon or nitrogen is filled to below 2 Pa.

[0062] The exhaust treatment process in S3 is as follows: the temperature in the crucible 1 is heated to 2070° C. by the first heating device 71, and the constant temperature is maintained at 2070° C. for 5 minutes, and then the upper insulation device 6 and the lower insulation device 8 are evacuated. When the air pressure is lower than 5 kPa, the evacuation is stopped.

[0063] The heating time to the first temperature in S4 is 5 hours, the heating rate is 90°C / h, and the first temperature is 2070°C. During S4, the temperature in the upper insulation device 6 is controlled to be 1770°C by the second heating device 61.

[0064] The second temperature in S5 is 30°C higher than the first temperature. After reaching the second temperature, the temperature is kept for 7 minutes and then the seed crystal 3 is pulled up by the seed crystal rod 5. The pulling speed is 10mm / h. During S5, the temperature in the upper insulation device 6 is controlled to be 1950°C by the second heating device 61. When the temperature reaches the first temperature, thermal convection melts the alumina raw material in the crucible 1 into a melt, and the temperature in the upper insulation device 6 is controlled to be 1770°C by the second heating device 61, so that the temperature of the seed crystal 3 in the upper insulation device 6 can be controlled to be close to that of the crucible 1, while avoiding the melting of the seed crystal 3; by increasing the temperature by 30°C to reach the second temperature, a liquid film is formed between the melted seed crystal 3 and the melted growth raw material, thereby driving the growth of the crystal 4, and by pulling up the seed crystal 3, the crystal 4 is pulled to shrink, and the bubbles in the crystal 4 are initially released, thereby avoiding the phenomenon of bubbling of the finished crystal 4, improving the growth quality of the crystal 4, and improving the surface smoothness of the finished crystal 4; the temperature in the upper insulation device is controlled to be 1950°C by the second heating device, so that the seed crystal temperature is close to the crystal growth temperature, which is beneficial to the growth of the crystal during the pulling process.

[0065] The cooling rate of the first cooling in S6 is 5°C / h; the temperature T1 inside the mold 2 is recorded; after the crystal growth is completed in S7, the temperature is kept at T2+10°C for 12 minutes, and then the whole crystal is separated from the mold 2. At the temperature T2+10°C inside the mold 2, the crystal 4 is separated from the mold 2 at a pulling speed of 950mm / h, and the growth of the crystal 4 is completed.

[0066] The temperature of the middle heat preservation device 7 is lowered by 185°C based on the temperature of the crystal 4 when it is separated from the mold 2; the temperature in the upper heat preservation device 6 is lowered by 165°C based on the temperature of the crystal 4 when it is separated from the mold 2; the temperature is kept for 1.5 hours after the temperature is lowered, and the annealing is completed; after the annealing treatment, the first heating device 71 and the second heating device 61 are used to cool the crystal at a cooling rate of 110°C / h and 90°C / h respectively, and then the crystal is taken out after being placed for 12 hours. After being pulled out of the mold 2, the crystal 4 is grown and starts to cool down.

[0067] Embodiment three:

[0068] The same contents of this embodiment as those of the second embodiment are not repeated here; the differences between this embodiment and the second embodiment are as follows:

[0069] This embodiment provides a method for growing curved crystals using a guided mold method, wherein a seed crystal 3 is positioned 45 mm above a mold 2 through a seed crystal rod 5; S6: when the seed crystal is pulled to a length of 9 mm and the seed crystal necking size is 1 / 2 of the original size of the seed crystal, a cooling process is started;

[0070] Further, the angle between the upper surface of the growth material and the upper surface of the mold 2 is 175°, and the distance between the lower surface of the mold 2 and the bottom of the crucible 1 is 40 mm. When the distance between the lower surface of the mold 2 and the bottom of the crucible 1 is 40 mm;

[0071] The angle between the upper surface of the growing material and the upper surface of the mold 2 is 175°.

[0072] The S2 is evacuated to below 8 Pa, the inert gas is argon or nitrogen, and the flow rate of the inert gas is 4 L / min. Argon and nitrogen are filled to below 8 Pa.

[0073] The exhaust treatment process in S3 is as follows: the temperature in the crucible 1 is heated to 2100° C. by the first heating device 71, and the constant temperature is maintained at 2100° C. for 28 minutes, and then the upper insulation device 6 and the lower insulation device 8 are evacuated. When the air pressure is lower than 95 kPa, the evacuation is stopped.

[0074] The heating time to the first temperature in S4 is 8 hours, the heating rate is 280°C / h, and the first temperature is 2100°C. During S4, the temperature in the upper insulation device 6 is controlled to be 1890°C by the second heating device 61.

[0075] The second temperature in S5 is 140°C higher than the first temperature. After reaching the second temperature, the temperature is kept for 55 minutes and then the seed crystal 3 is pulled up by the seed crystal rod 5. The pulling speed is 95mm / h. During S5, the temperature in the upper insulation device 6 is controlled to be 1990°C by the second heating device 61. When the temperature reaches the first temperature, thermal convection melts the alumina raw material in the crucible 1 into a melt, and the temperature in the upper insulation device 6 is controlled to be 1890°C by the second heating device 61, so that the temperature of the seed crystal 3 in the upper insulation device 6 can be controlled to be close to that of the crucible 1, and the melting of the seed crystal 3 can be avoided; by increasing the temperature by 140°C to reach the second temperature, a liquid film is formed between the melted seed crystal 3 and the melted growth raw material, thereby driving the growth of the crystal 4, and by pulling up the seed crystal 3, the crystal 4 is pulled to shrink the diameter, and the bubbles in the crystal 4 are initially released, thereby avoiding the phenomenon of bubbling of the finished crystal 4, improving the growth quality of the crystal 4, and improving the surface smoothness of the finished crystal 4; the temperature in the upper insulation device is controlled to be 1990°C by the second heating device, so that the seed crystal temperature is close to the crystal growth temperature, which is beneficial to the growth of the crystal during the pulling process.

[0076] The cooling rate of the first cooling in S6 is 45°C / h; the temperature T inside the mold 2 is recorded; after the crystal growth is completed in S7, the temperature is kept at T2+10°C for 18 minutes, and the whole crystal is separated from the mold 2. By reducing the diameter by 5mm, the crystal 4 is slowly placed on the same width as the mold 2 and then grown in equal diameter; the crystal 4 is separated from the mold 2 at a pulling speed of 1050mm / h at the temperature T2+10°C inside the mold 2, and the growth of the crystal 4 is completed.

[0077] The temperature of the middle heat preservation device 7 is reduced by 210°C based on the temperature of the crystal 4 when it is separated from the mold 2; the temperature in the upper heat preservation device 6 is reduced by 170°C based on the temperature of the crystal 4 when it is separated from the mold 2; the temperature is kept for 3 hours after the temperature is reduced, and the annealing is completed; after the annealing treatment, the first heating device 71 and the second heating device 61 are used to cool the crystal at a cooling rate of 350°C / h and 90°C / h respectively, and then the crystal is taken out after being placed for 23 hours. After being pulled out of the mold 2, the crystal 4 is grown and starts to cool down.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the above embodiments, or replace some of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for growing a curved crystal using a guided-mode method, characterized in that: S1: placing a growth raw material into a crucible (1), placing a mold (2) in the crucible (1), fixing a seed crystal (3) on one end of a seed crystal rod (5), wherein the seed crystal rod (5) is connected to a lifting mechanism; placing the seed crystal (3) 3-50 mm above the mold (2) through the seed crystal rod (5), wherein the mold (2) is provided with a curved inner cavity; The crucible (1) is located in a central heat preservation device (7); S2: evacuating the upper heat preservation device (6) and the middle heat preservation device (7) and then filling them with inert gas; S3: perform exhaust treatment; S4: raising the temperature in the crucible (1) to a first temperature to melt the growth raw material in the crucible (1); S5: after the seed crystal (3) is lowered to the point where it contacts the upper surface of the mold (2) by the seed crystal rod (5), the temperature in the crucible (1) is raised again to a second temperature, and then the seed crystal (3) is pulled up by the seed crystal rod (5); S6: When the seed crystal (3) is pulled down to a length of 5-10 mm and the necking size of the seed crystal (3) is 1 / 3 to 1 / 2 of the original size of the seed crystal (3), cooling is started once, and the width of the growing crystal (4) is made the same as the width of the mold (2), and cooling is stopped, and the growth temperature T1 of (2) is recorded; S7: The crystal continues to grow, and the temperature control after equalization is adjusted based on the temperature of T1 through the data fed back by the sensor. After the crystal growth is completed, the temperature is T2, and the whole crystal (4) is separated from the mold (2); S8: After cooling, annealing is performed.

2. A method for growing curved crystals using a guided mode method according to claim 1, characterized in that: The crucible (1) and the first heating device (71) are arranged in the cavity of the middle heat preservation device (7), and the first heating device (71) is arranged outside the crucible (1); The second heating device (61) is arranged 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-insulating device (7) and the upper heat-insulating 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; Preferably, a lower heat-insulating device (8) is connected below the middle heat-insulating device (7), a power supply device (81) is provided inside the lower heat-insulating device (8), and the first heating device (71) and the second heating device (61) are both electrically connected to the power supply device (81).

3. The method for growing a curved surface crystal by a guided mode method according to claim 1, characterized in that: The growth raw material in S1 is aluminum oxide.

4. The method for growing a curved surface crystal by a guided mode method according to claim 1, characterized in that: The S2 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 a curved surface crystal by a guided mode method according to claim 1, characterized in that: The exhaust gas treatment process in S3 is as follows: The temperature inside the crucible (1) is heated to 2050-2200°C by a first heating device (71), and the constant temperature is maintained at 2050-2200°C for 25-35 minutes.

6. The method for growing a curved surface crystal by a guided mode method according to claim 1, characterized in that: The heating time to the first temperature in S4 is 4-10 hours, the heating rate is 80-300°C / h, and the first temperature is 2050-2200°C; During the S4 process, the temperature in the upper heat preservation device (6) is controlled to be 1800° C.-2000° C. by the second heating device (61).

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

8. The method for growing a curved surface crystal by a guided mode method according to claim 1, characterized in that: The cooling rate of the first cooling in S6 is 1-50°C / h; the growth temperature T1 is recorded; After the crystal growth is completed in S7, the temperature is kept at T2+10° C. for 10-20 minutes, and then the whole crystal (4) is separated from the mold (2).

9. The device for curved surface growth using guided mode method according to claim 1, characterized in that: After the crystal (4) in S7 is finished, the temperature in the crucible (1) is increased by 9-11° C., and then the crystal (4) is pulled up by the seed crystal rod (5) at a pulling speed of 900-1100 mm / h and separated from the mold (2).

10. The device for curved surface growth using guided mode method according to claim 1, characterized in that: In S8, after the crystal (4) is separated from the mold (2), the temperature of the middle heat preservation device (7) is lowered by the first heating device (71) and the second heating device (71), and the temperature of the middle heat preservation device (7) is lowered by 180-220° C. based on the temperature when the crystal (4) is separated from the mold (2); The temperature in the upper heat preservation device (6) is lowered by the first heating device (71) and the second heating device (61), and the temperature in the upper heat preservation device (6) is lowered by 160-180° C. based on the temperature when the crystal (4) is separated from the mold (2); After cooling, the material is kept warm for 1-4 hours to complete annealing. After annealing, the material is cooled by the first heating device (71) and the second heating device (61) at a cooling rate of 100-400°C / h and 80-100°C / h respectively, and then placed for 10-24 hours before being taken out.

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