Crystal and crucible separating device and induction heating coil thereof

Abstract

The utility model discloses a crystal and crucible separating device and an induction heating coil thereof. The crucible comprises a side wall and a bottom plate, the crystal is bonded in the crucible before separation and is in direct contact with the bottom plate, the induction heating coil comprises a side surface coil and a bottom surface coil, the side surface coil and the side wall form a profile, the bottom surface coil and the bottom surface coil form a profile, and the side surface coil and the bottom surface coil form a shape. And a containing space defined by the side surface coil and the bottom coil can be used for containing the crucible in a profiling manner. According to the separation scheme provided by the utility model, crystals and the crucible are subjected to non-destructive separation in an induction heating manner, so that complete separation of crystal ingots and repeated recycling of the crucible can be realized; and the crucible cost consumed when crystals such as sapphire, spinel and yttrium aluminum garnet are grown by heat treatment methods such as a heat exchange method, a Bridgman-Stockbarger method and a temperature gradient method can be obviously reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of crystal growth, in particular to a device for separating a crystal from a crucible and an induction heating coil thereof. Background Art

[0002] Various compound crystals are widely used in many fields such as semiconductors, optics, and electronics. For example, sapphire crystals have excellent physical and chemical properties such as high optical transmittance, mechanical strength, high temperature resistance (melting point is 2050°C), small thermal expansion coefficient, high thermal conductivity, good chemical stability, and radiation resistance. They are widely used in national defense, aerospace, and LED fields.

[0003] The heat exchange method is an important method for growing high-quality sapphire crystals. It has the advantages of fast growth rate, few crystal defects, stable temperature field, adjustable temperature gradient inside the crucible, and high degree of automation. It has a very important market in the growth of high-quality optical-grade sapphire crystals. However, its disadvantage is that during the growth process, the raw materials are severely adhered to the crucible after they are all crystallized into crystals. In order to obtain a complete sapphire crystal, the crucible must be physically destroyed. The crucible material is high-temperature resistant molybdenum material, which is prepared into a crucible of a specific shape required for growth by the heat exchange method through high-temperature spinning technology. The cost is very high. For example: the cost of a spun molybdenum crucible with a diameter of 380mm and a height of 380mm is 11,000-12,000 yuan; the cost of a spun molybdenum crucible with a diameter of 440mm and a height of 450mm is as high as 15,000-18,000 yuan; in addition, the cost of molybdenum crucibles or tungsten crucibles prepared by powder metallurgy is even higher.

[0004] The biggest technical bottleneck in the existing heat exchange crystal growth technology is that the crucible can only be used once, which hinders the popularization of this method and leads to high crystal growth costs. According to practical tests, the cost of the crucible in the heat exchange method accounts for 30-40% of the cost of the sapphire crystal.

[0005] At the same time, the same serious adhesion between the crystals and the crucible also exists in the growth of sapphire, spinel, yttrium aluminum garnet and other crystals by the crucible descent method and the temperature gradient method. The only way to obtain the crystal ingot is to destroy the crucible, which faces the same problem.

[0006] In addition, when the crystal growth process encounters abnormal conditions or the process parameters cannot meet the conditions for crystal crystallization, the crystals in the crucible will have poor quality, numerous defects, crystal cracking, crystal scrapping, and even raw materials not crystallizing, forming unfinished products in the crucible. At this time, the crucible must be physically destroyed (molybdenum crucible fragments have recycling value) or the crucible must be discarded, which significantly increases production costs. Utility Model Content

[0007] In view of the deficiencies in the prior art, the purpose of the utility model is to provide a device for separating a crystal from a crucible and an induction heating coil thereof.

[0008] In order to achieve the above-mentioned utility model purpose, the technical solution adopted by the utility model includes:

[0009] In a first aspect, the utility model provides an induction heating coil for separating a crystal from a crucible, the crucible comprising a side wall and a bottom plate, the crystal being bonded in the crucible and in direct contact with the bottom plate before separation, the induction heating coil comprising a side coil and a bottom coil, the side coil conforming to the side wall, the bottom coil conforming to the bottom plate, and the accommodation space enclosed by the side coil and the bottom coil being able to conform to the crucible.

[0010] Furthermore, the side coil is of a spiral spring type, and the bottom coil is of a flat spiral type.

[0011] Furthermore, the side coil and the bottom coil are connected in series.

[0012] Furthermore, the side coil and the bottom coil are an integrated coil structure formed by bending an integrated hollow metal tube.

[0013] Furthermore, a cooling medium inlet and a cooling medium outlet are respectively provided at both ends of the hollow metal tubular object.

[0014] Furthermore, the turn density of the side coil is 1.5-2.5 times the turn density of the bottom coil.

[0015] In a second aspect, the utility model further provides a crystal and crucible separation device, which is used to separate the crystal and the crucible by induction heating, wherein the crystal is adhered to the inner wall of the crucible before separation; the separation device comprises:

[0016] The induction heating coil is configured to conform to the crucible, and when induction heating is performed, the induction heating coil surrounds the crucible;

[0017] A bearing structure, used for bearing the crucible and the crystal inside the crucible during induction heating;

[0018] and a high-frequency power supply unit, which is used to provide high-frequency alternating current to the induction heating coil to achieve the induction heating.

[0019] Based on the above technical solution, compared with the prior art, the beneficial effects of the utility model at least include:

[0020] The separation method provided by the utility model is a method for non-destructively separating crystals from crucibles by induction heating, which can achieve complete separation of crystal ingots and multiple recycling uses of crucibles, and can significantly reduce the cost of crucibles consumed when growing crystals such as sapphire, spinel and yttrium aluminum garnet by heat treatment methods such as heat exchange method, crucible descent method and temperature gradient method.

[0021] The above description is only an overview of the technical solution of the utility model. In order to enable those skilled in the art to more clearly understand the technical means of the present application and implement them according to the contents of the specification, the following is a preferred embodiment of the utility model with detailed drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the combined state of a crystal and a crucible provided in a typical implementation case of the utility model;

[0023] Figure 2a It is a front view structural schematic diagram of an induction heating coil in a separation device provided in a typical embodiment of the present invention;

[0024] Figure 2b It is a schematic diagram of the top view of the induction heating coil in the separation device provided in a typical embodiment of the present invention;

[0025] Figure 3 It is a schematic diagram of the combined state of the induction heating coil and the crucible in the separation device provided in a typical implementation case of the utility model;

[0026] Figure 4 It is a schematic diagram of the overall composition structure of a separation device provided in a typical implementation case of the utility model.

[0027] Explanation of the accompanying drawings: 1. Crystal; 2. Crucible; 3. Outer wall; 4. Inner wall; 5. Outer bottom; 6. Inner bottom; 7. Bottom coil; 8. Side coil; 9. Protection chamber; 10. Support platform; 11. Slide rail; 12. Power supply; 13. Control system; 14. Mechanical pump; 15. Diffusion pump; 16. Inflating valve; 17. Pressure gauge; 18. Transformer. DETAILED DESCRIPTION

[0028] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the utility model after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0030] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0031] See also Figure 1-Figure 3 As shown, the embodiment of the utility model provides a method for separating a crystal from a crucible, wherein the crystal is adhered to the inner wall of the crucible before separation, and the crucible is a conductor; the separation method comprises the following steps:

[0032] The inner wall of the crucible 2 in contact with the crystal 1 is heated by induction heating, so that at least a portion of the surface of the crystal 1 in contact with the inner wall is melted, thereby separating the crystal 1 from the crucible 2.

[0033] The above method designs an induction heating coil for separating a crystal 1 from a crucible 2, wherein the crucible 2 includes a side wall and a bottom plate. Before separation, the crystal is bonded in the crucible and is in direct contact with the bottom plate. The induction heating coil includes a side coil 8 and a bottom coil 7. The side coil 8 is contoured to the side wall, and the bottom coil 7 is contoured to the bottom plate. The accommodating space formed by the side coil 8 and the bottom coil 7 can contourably accommodate the crucible 2.

[0034] The above crystal 1 is usually a compound with obvious crystal characteristics, such as sapphire, spinel and yttrium aluminum garnet ingots grown by heat exchange method, crucible descent method and temperature gradient method. For example, the sapphire material is a typical single crystal 1 material with anisotropic crystal 1 characteristics and a melting point of 2050°C. It takes a special method to separate the sapphire material from the crucible 2 material used in the growth production process, and other crystals 1 are similar.

[0035] A more specific typical example is: the heat exchange method is an important method for mass production of large-size, high-quality sapphire crystals 1, and its advantages are: the crystal 1 has high optical quality, high optical uniformity, a diameter of 380-500mm, good growth technology stability, high repeatability, and can stably produce 100Kg-200kg of optical-grade sapphire crystals 1 in batches. The growth cycle is about 20 days, and the maximum growth temperature is 2150°C. During the growth process, a high-temperature resistant molybdenum crucible 2 (the melting point of molybdenum material is 2623°C) is required to load the aluminum oxide raw material required to grow sapphire. Its characteristic is that all the raw materials in the crucible 2 are crystallized into sapphire crystals 1, and the raw material utilization rate reaches 100%. The disadvantage of this method is that after the growth of the crystal 1 is completed, the sapphire and the molybdenum crucible 2 are severely adhered.

[0036] The method provided by the utility model utilizes the principle of high-frequency induction heating and utilizes a unique special-shaped induction heating coil to perform induction heating on a conductor crucible 2 (including but not limited to a molybdenum crucible 2, a tungsten crucible 2 or a tungsten-molybdenum alloy crucible 2, and of course a graphite crucible 2 also belongs to a conductor crucible 2) containing a crystal 1. The heat of the inner wall of the crucible 2 is conducted to the crystal 1 by conduction. The crystal 1 is heated and the surface temperature continues to rise. When the temperature rises to the melting point of the crystal 1 or the raw material, a physical change from a solid phase to a liquid phase will occur, and the crystal 1 will fall off the crucible 2 under the action of the detachment force. Since the thermal conductivity of the crystal 1 is significantly lower, the internal temperature of the crystal 1 will not rise significantly, and the performance of the crystal 1 will not be affected.

[0037] The basic technical concept of the utility model is to use the skin effect of induction heating to instantly heat the crucible 2 to a temperature above the melting point of the crystal 1 in a short time. The high-temperature crucible 2 then conducts the heat to the surface of the crystal 1 material by conduction. Since the thermal conductivity of the crystal 1 material is usually significantly lower than that of metal, when the part of the crystal 1 material in contact with the crucible 2 reaches the melting point, this part of the crystal 1 is converted into a melt with fluidity and can leave the crucible 2.

[0038] In order to ensure good utilization of the crystal 1 and reduce the impact of the residual crystal 1 on the crucible 2, it is usually required that the sapphire be intact after being separated from the crucible 2 without defects such as cracks.

[0039] Induction heating has the characteristics of skin effect. Only the surface part of the heated material is heated instantly due to the existence of eddy current, and the heating speed is fast and the thermal efficiency is high. Therefore, through actual experiments, it is found that this heating method is the most advantageous method for demolding the crystal 1. Other heating methods, such as resistance wire heating, are inefficient on the one hand, and it takes a long time to heat the temperature to a suitable temperature. Even if the suitable temperature can be reached, the inside of the crystal 1 will be heated. Once the inside is heated and cooled again, the structure of the crystal 1 will change from the original crystal 1 structure to the amorphous 1 structure, resulting in changes in material properties and unusable.

[0040] Therefore, the key to achieving demolding while avoiding affecting the internal structure of the crystal 1 is to select the induction heating method with skin effect to perform localized heating on the contact surface between the crystal 1 and the crucible 2. In addition, in some preferred schemes, the depth of induction heating should also be regulated to concentrate it near the above-mentioned contact surface, so as to achieve more precise heating.

[0041] In addition to heating and demoulding the finished product of the complete crystal, some unfinished products are easily produced in the actual production and preparation process. Therefore, in some embodiments, the crystal 1 includes a complete crystal formed by growth or an unfinished product formed during the growth of the complete crystal. This means that the technical solution provided by the utility model can not only separate the finished product, but also the unfinished product. Of course, the requirements for the heating area for the separation of the unfinished product are usually lower than those for the finished product crystal 1, and it is usually not required to avoid affecting the internal crystal 1 structure of the unfinished product.

[0042] More specifically, in some embodiments, the separation method may include the following detailed steps:

[0043] While the induction heating is being performed, the crystal 1 is continuously subjected to a combined force in a direction away from the bottom of the crucible 2 until at least a portion of the surface of the crystal 1 melts and detaches.

[0044] Regarding the manner of applying the above-mentioned combined force, in some embodiments, when the induction heating is performed, the crucible 2 is in a state where its opening faces the direction of gravity; when at least a portion of the surface of the crystal 1 melts, the crystal 1 falls off from the crucible 2 along the direction of gravity.

[0045] Of course, in addition to the gravity detachment method, various other alternative methods can also be used, such as negative pressure traction, centrifugal force, etc.

[0046] In order to avoid oxidation of the crucible 2, in some embodiments, the induction heating is performed in a vacuum and / or protective atmosphere.

[0047] Regarding the specific structural features of the crystal 1 and the crucible 2, in some embodiments, the crystal 1 is a columnar body having a side wall and an end face, the crucible 2 has an inner wall 4 and an inner bottom 6, the side wall is adhered to the inner wall 4, the end face is adhered to the inner bottom 6, and a demolding angle greater than 90° is formed between the inner wall 4 and the inner bottom 6. Specifically, in the figure, θ is generally 93-95 degrees. The wall thickness of the crucible 2 is 2-5 mm.

[0048] It is generally believed that since the heating rate is related to the power density, maintaining a uniform power density at each location can allow different locations to reach the melting temperature at the same time, thereby achieving synchronous demolding. However, the inventors of the present utility model have found in practice that this method can achieve a relatively good separation effect for crystals 1 with a smaller volume, such as crystals 1 with a diameter and a height of less than 100 mm, but for crystals 1 with a size exceeding the above size (either the diameter or the height exceeds the above range), it sometimes leads to asynchronous demolding of the side wall and the end surface.

[0049] This may be because, from a microscopic point of view, the side wall and the inner wall 4 are separated by sliding, and the end face and the inner bottom 6 are separated by plane, and the separation modes of the two are different. Therefore, when the melting temperature is reached, whether the larger contact surface is separated or not also has a certain timing difference. In addition, the lattice structure of different faces of the crystal 1 is also likely to cause a certain influence, especially for the oriented single crystal 1, the crystal planes of the side wall and the bottom are different, which also leads to the difference in heating rate under the same power density, or the different crystal planes have different bonding forces with the surface of the crucible 2. All these factors lead to the phenomenon of asynchronous demolding when heating with uniform power density.

[0050] Specifically, when the above-mentioned end face at the bottom of the crucible 2 reaches the demolding condition first, the side wall surface will continue to be heated until the temperature of the side crystal 1 reaches the melting point, and more sapphire crystals 1 at the bottom of the crucible 2 will further melt into a high-temperature melt, and the crystal 1 can be separated from the crucible 2, which will cause the height of the crystal 1 to decrease and the utilization rate of the crystal 1 to decrease. In addition, it will cause the molten crystal 1 to adhere to and deposit at the bottom of the crucible 2, affecting the secondary utilization of the crucible 2.

[0051] When the side wall reaches the demolding condition first, the end face of the crystal 1 at the bottom of the crucible 2 will continue to be heated until the temperature reaches the melting point, and the crystal 1 can be separated from the crucible 2. At this time, due to the excessive heating of the side wall and the density skin effect based on induction heating, the heat is concentrated to form a large temperature gradient. Therefore, the crystal 1 will be deformed or even cracked. In severe cases, the crystal 1 will be scrapped and have no use value.

[0052] Therefore, in order to maximize the utilization rate and yield of complete crystals and avoid excessive residue of molten crystals 1 on the surface of crucible 2, in some embodiments, during the induction heating, the power density of the inner wall surface 4 and the inner bottom surface 6 are modulated to be different so that the side wall surface and the end surface reach the melting state at the same time.

[0053] Based on the actual experience of the inventors of the present utility model, for most crystals 1, what mainly happens is that the bottom end surface reaches the demolding condition first. Therefore, for most crystals 1, such as sapphire, spinel and yttrium aluminum garnet, it is generally necessary to set the power density corresponding to the side wall surface to be higher than the power density corresponding to the end surface, especially for crystals with strong orientation, such as single crystals.

[0054] Of course, it is not ruled out that for different crystals 1, the side may reach the demolding condition first. Based on the technical concept disclosed by the utility model, the focus is on the different implementation means of regulating the power density of the side and bottom, which can be regulated in combination with actual phenomena.

[0055] As for the specific regulation ratio, in some embodiments, for example, for crystals such as sapphire, spinel and yttrium aluminum garnet, especially crystals with strong anisotropy, such as single crystals, the power density corresponding to the inner bottom surface 6 is 40-60% of the power density corresponding to the inner wall surface 4.

[0056] By modulating the power density to precisely control the melting of the side and bottom surfaces at the same time, the integrity of the crystal 1 can be ensured. In addition, it can also ensure that the thermal stress and mechanical stress on each part of the crucible 2 during the process of induction heating and separation from the sapphire are minimized, and the deformation of the crucible 2 is minimized, which is beneficial to increasing the number of recycling times and is also beneficial to the process control of the next round of crystal 1 growth and the quality of the crystal 1.

[0057] In addition to the proportional relationship of power density on different surfaces, the numerical range of power density is also important for obtaining a better separation effect. In the experiment, it was found that the heating power density is the key parameter that affects whether the crystal and the crucible can be separated intact. After many experiments, a more reasonable heating power density range can be found. The minimum power density is 20 watts per cubic centimeter and the maximum power density is 120W / cm 3 , the optimal value is 50-80W / cm 3 . Power density is less than 20W / cm 3 In this case, the heating efficiency is low, the temperature rises slowly, and there are many melting points in the ingot, resulting in low ingot utilization. The power density is higher than 120W / cm 3 In this case, on the one hand, the requirements for the heating equipment are high and the cost is high. On the other hand, too fast heating will cause thermal stress concentration inside the ingot. The thermal stress and the residual stress in the ingot growth process will cause local cracking of the ingot and also reduce the utilization rate of the ingot.

[0058] It can be seen that in some embodiments, the power density ranges from 20 to 120 W / cm 3 In this range, the actual power density of different surfaces can be adjusted based on the above proportional relationship.

[0059] Continue to see Figure 1-Figure 3 , and combined with Figure 4 As shown, corresponding to the above separation method, the second aspect of the embodiment of the utility model further provides a crystal and crucible separation device, which is used to separate the crystal 1 and the crucible 2 by induction heating, and the crystal 1 is adhered to the inner wall of the crucible 2 before separation; the separation device comprises:

[0060] An induction heating coil is disposed in a conformal manner with the crucible 2 and surrounds the crucible 2 during induction heating.

[0061] The supporting structure is used to support the crucible 2 and the crystal 1 inside the crucible 2 during induction heating.

[0062] and a high-frequency power supply unit, which is used to provide high-frequency alternating current to the induction heating coil to achieve the induction heating.

[0063] In some embodiments, the separation device may further include a protection chamber 9, in which the induction heating coil and the supporting structure are disposed; the protection chamber 9 can be evacuated and / or replaced with a protective atmosphere.

[0064] As for the specific structure and matching relationship between the crucible 2 and the induction coil, in some embodiments, the crucible 2 has an outer wall surface 3 and an outer bottom surface 5, and the induction heating coil includes a bottom coil 7 and a side coil 8. The bottom coil 7 is a planar spiral shape, corresponding to the shape of the outer bottom surface 5, and the side coil 8 is a spiral spring shape, corresponding to the shape of the outer wall surface 3; the bottom coil 7 and the side coil 8 are at equal distances from the outer wall surface 3 or the outer bottom surface 5.

[0065] Further corresponding to the above-mentioned refined power density control method, in some embodiments, in order to form the above-mentioned power density difference, the bottom coil 7 and the side coil 8 are connected in series, and the turn density of the side coil 8 is 1.5-2.5 times higher than the turn density of the bottom coil 7, so that the power density of the side wall surface is larger.

[0066] Generally, the appropriate turn density ranges from a minimum of 1 turn per centimeter to a maximum of 15 turns per centimeter, and the optimal value range is 5-12 turns per centimeter. Of course, even if it is different from this, as long as a reasonable design is made according to conditions such as the crucible size, the corresponding function can be achieved.

[0067] Of course, there are many ways to form the above-mentioned power density difference. The above-mentioned method is a preferred method that is relatively convenient to implement and relatively precise in control. In addition, two independent bottom coils 7 and side coils 8 can be set to electrically control the power of the two coils respectively, and then the power density of the two coils is adjusted to present the above-mentioned proportional relationship, so as to achieve the effect that the side wall surface and the end face of the crystal 1 simultaneously reach the separation condition.

[0068] As some typical examples of the above technical solutions, the general coil used in the utility model can be processed from a copper tube, which consists of a side coil 8 and a bottom coil. The side coil 8 heats the side of the crucible 2, and the bottom coil heats the bottom of the crucible 2. The height H3 of the coil side is greater than the height H1 of the crystal 1, and the diameter C of the coil bottom is greater than the diameter A of the crucible 2. Figure 2a , Figure 2b and Figure 3 shown.

[0069] The number of turns of the side coil 8 is related to the coil height and the copper tube diameter. The number of turns of the side coil = height divided by the copper tube diameter. The number of turns of the bottom coil 7 is related to the coil diameter and the copper tube diameter. The number of turns of the bottom coil = coil diameter / (coil copper tube diameter × 2)

[0070] Specifically, for example, a molybdenum crucible 2 with a diameter of 380 mm and a height of 380 mm and a crystal 1 with a diameter of 375 mm and a height of 260 mm for induction heating, the diameter of the circular copper tube used is 10 mm, the diameter of the bottom of the coil is 400 mm, and the number of turns at the bottom is 400 (10×2) = 20 turns. The height of the coil is 300 mm, and the number of turns at the side is 300 / 10 = 30 turns.

[0071] Of course, if it is necessary to control the side surface and the bottom surface to have different turn densities to obtain different power densities, the spacing between the side surface or the bottom surface can be appropriately adjusted to adjust the number of turns.

[0072] The relative position relationship between the induction coil and the crucible 2 is as follows: the side coil 8 of the induction coil is 5-10 mm away from the wall of the crucible 2, and the spacing on the left and right sides is equal. The bottom coil 7 is 5-10 mm away from the bottom of the crucible 2, and the spacing between the bottom coil 7 and the side coil 8 and the corresponding crucible 2 is usually equal.

[0073] The method of the utility model is suitable for the crucible 2 and the crystal 1 after crystallization used in various crystal 1 growth methods such as heat exchange method, crucible descent method and temperature gradient method, and is characterized in that the crucible 2 is made of conductive material, and the crystal 1 and the crucible 2 are in a state of adhesion. The device of the utility model is applicable to both the case where the crystal 1 is intact and the case where the crystal 1 is cracked. The device of the utility model can also be applied to raw materials and crucibles 2 that fail to grow crystal 1 due to various reasons, or even uncrystallized, and is characterized in that the raw materials and the crucible 2 are in a state of adhesion. In order to reuse the crucible 2, it is suitable to use the method to remove the uncrystallized growth raw materials from the crucible 2 to obtain a complete crucible 2, which can be used for a second time after relevant treatment, thereby reducing the cost of using the crucible 2.

[0074] As an example of a separation method, the separation method is implemented using a separation device as shown in Figure 4, and the specific steps include:

[0075] The first step: invert the molybdenum crucible 2 bonded with the sapphire crystal 1 on a supporting platform 10 that can move up and down, that is, the top of the crucible 2 is downward and the bottom of the crucible 2 is upward.

[0076] Step 2: Slowly move the slide rail 11 upward, and move the support platform 10 fixedly connected to the slide rail 11 upward, and place the crucible 2 inside the induction coil, such as Figure 3 As shown, the gap between the bottom of the crucible 2 and the bottom of the induction coil is adjusted to be between 5-10 mm, and the gap between the side of the crucible 2 and the side of the coil is adjusted to be between 5-10 mm.

[0077] Step 3: The protective chamber 9 equipped with the induction coil and the crucible 2 is sealed and evacuated. The vacuum system is composed of a mechanical pump 14 and a diffusion pump 15 or a molecular pump two-stage system. The mechanical pump 14 is started first to evacuate the vacuum to a degree less than 5 Pa, and then the diffusion pump 15 or the molecular pump is started to evacuate the vacuum to a degree less than 3×10 -3 Pa, high purity 99.99% argon or nitrogen is filled into the protection chamber 9 through the charging valve 16, and the charging valve 16 is closed when the pressure gauge 17 of the protection chamber 9 shows that the pressure in the furnace is positive pressure, generally 0.01-0.05Mpa. The purpose of filling argon or nitrogen is to prevent the molybdenum crucible 2 from being oxidized due to the increase in temperature during the induction heating process.

[0078] Step 4: Open the water inlet of the induction coil, control the water inlet temperature at 15-25 degrees, and the flow rate at 5-10L / min. Start the equipment power supply 12 through the control system 13 and apply current through the transformer 18. The induction coil can generate eddy currents in the crucible 2, instantly heating the molybdenum material at the bottom and side of the crucible 2. The melting point of sapphire crystal 1 is 2050℃. When the temperature of the molybdenum material reaches 2050℃, the sapphire crystal 1 adhered to the inner wall of the crucible 2 and the inner wall of the bottom of the crucible 2 will become a melt due to the heat rise. Since there is a cavity H2 between the crystal 1 in the crucible 2 and the mouth of the crucible 2 ( Figure 1 ), the entire sapphire crystal 1 is separated from the molybdenum crucible 2 under the action of gravity and falls on the carrier 10. That is, in some ways, the supporting structure includes a horizontally arranged carrier 10, and the crucible can be supported on the carrier surface with the opening pointing in the direction of gravity. Of course, even a slight tilt does not affect the falling of the crystal 1. In addition, using a negative pressure suction cup or the like to pull and separate the crystal 1 in a non-gravity direction is also an equivalent method.

[0079] Step 5: Cut off the power supply 12, fill the protection chamber 9 with air at room temperature and pressure through the inflation valve 16 until the internal and external pressures are balanced, then open the protection chamber 9, move the support platform 10 downward, and take out the sapphire crystal 1.

[0080] In the above technical solution, the induction heating frequency used is closely related to the wall thickness of the crucible 2. The frequency range used in the utility model is usually 10KHz-62.5KHz. According to the induction heating principle, the induction heating depth d and the induction frequency f have the following relationship formula:

[0081]

[0082] Where: f is the frequency, the unit is Hz; d is the heating depth, the unit is millimeter (mm).

[0083] When f=10KHz, the heating depth d=5mm, which is suitable for a molybdenum or tungsten crucible 2 with a wall thickness of 5mm. The crystal 1 in the crucible 2 is not electrically conductive and is not inductively heated. There is only heat conduction from the inner wall of the crucible 2 to the crystal 1. Due to the short heating time, the temperature of the surface of the crystal 1 (including the bottom side) rises, while the temperature of most other crystals 1 does not change.

[0084] When f = 62.5KHz, the heating depth d = 2mm, which is suitable for molybdenum or tungsten crucibles 2 with a wall thickness of 2mm. The crystal 1 in the crucible 2 is not inductively heated because it is non-conductive. There is only heat conduction from the inner wall of the crucible 2 to the crystal 1. Due to the short heating time, the temperature of the surface of the crystal 1 (including the bottom side) rises, and the temperature of most other crystals 1 does not change.

[0085] In order to ensure comprehensive heating, the coil height H1 is usually greater than the ingot thickness H2, H1-H2=20-30mm.

[0086] As a further application of the above technical solution, the embodiment of the utility model further provides a crystal growth method, which comprises the following steps:

[0087] A crystal 1 is formed in a crucible 2 by heat treatment.

[0088] The separation method provided in any of the above embodiments is used to separate the crystal 1 from the crucible 2 through induction heating to obtain independent crystals 1 and crucibles 2.

[0089] The crystal 1 is, for example, a complete crystal, which is used for slicing as a substrate after separation; it can also be an unfinished product produced when growing the above-mentioned complete crystal, such as an unusable product caused by poor crystallization, unexpected process interruption, etc., which can be separated by the above method to obtain a reusable crucible 2.

[0090] After the physical separation of the crystal 1 and the crucible 2 is achieved, the inner wall of the crucible 2 is polished with diamond paper, and after weak acid immersion cleaning and drying, the raw materials required for the growth of the crystal 1 are loaded again and can be recycled for the second time, thereby reducing the cost of the crucible 2 consumed by a single crystal 1. According to experience, the conductive crucible 2 with the adhered crystal 1 separated by the method provided by the utility model can be recycled at least 2-5 times.

[0091] The technical solution of the utility model is further described in detail below through several embodiments and in combination with the accompanying drawings. However, the selected embodiments are only used to illustrate the utility model, and do not limit the scope of the utility model.

[0092] Example 1

[0093] This embodiment illustrates a separation process of a sapphire crystal 1, which is specifically as follows:

[0094] The first step: Invert the molybdenum crucible 2 (crucible 2 diameter 380mm, height 380mm) with a single crystal sapphire crystal 1 (crystal 1 diameter 375mm height 235mm, weight 100Kg) grown by heat exchange method on a supporting platform 10 that can move up and down, that is, the top of crucible 2 is facing down and the bottom of crucible 2 is facing up.

[0095] Step 2: Slowly move the slide rail 11 upward, and move the support platform 10 fixedly connected to the slide rail 11 upward, and place the crucible 2 inside the induction coil, such as Figure 3 As shown, the size of the induction coil is a bottom diameter of 390 mm, a height of 260 mm, a diameter of the copper tube constituting the induction coil of 10 mm, the number of turns of the side coil 8 is 26, the number of turns of the bottom coil 7 is 19, the gap between the bottom of the crucible 2 and the bottom of the induction coil is adjusted to 5 mm, and the gap between the side of the crucible 2 and the side of the coil is 5 mm.

[0096] Step 3: The protective chamber 9 equipped with the induction coil and the crucible 2 is closed and evacuated. The vacuum system is composed of a two-level system of a mechanical pump 14 and a diffusion pump 15. The mechanical pump 14 is started to evacuate to 4 Pa, and then the diffusion pump 15 is started to evacuate to a high vacuum of 2×10 -3 Pa, high purity 99.99% argon is filled into the protection chamber 9 through the charging valve 16, and the charging valve 16 is closed when the furnace pressure gauge 17 shows that the pressure in the furnace is positive and the pressure is 0.01Mpa. The purpose of filling argon is to prevent the molybdenum crucible 2 from being oxidized due to the increase in temperature during the induction heating process.

[0097] Step 4: Open the water inlet of the induction coil, the water inlet temperature is 15 degrees, the flow rate is 5L / min, and the equipment power 12 is started. The induction coil can produce eddy currents in the crucible 2, and instantly heat the molybdenum material at the bottom and side of the crucible 2. The melting point of the sapphire crystal 1 is 2050°C. When the temperature of the molybdenum material reaches 2050°C, the sapphire crystal 1 adhered to the inner wall of the crucible 2 and the inner wall of the bottom of the crucible 2 will become a melt due to the heat rise. Under the action of gravity, the entire sapphire crystal 1 is separated from the molybdenum crucible 2 and lands on the supporting platform 10.

[0098] Step 5: Cut off the power supply 12, fill the furnace body with air at room temperature and pressure through the inflation valve 16 until the internal and external pressures are balanced, open the furnace body, slowly move the supporting platform 10 downward, and take out the complete sapphire crystal 1, weighing 100 kg.

[0099] Comparative Example 1

[0100] This comparative example is substantially the same as Example 1, except that:

[0101] The induction coil is removed and replaced with a resistance wire of the same winding method, and the resistance wire is in close contact with the crucible 2 to achieve heat conduction. The resistance wire is heated slowly, and the maximum temperature is far below the melting point of sapphire, 2050 degrees. Generally, the resistance wire is heated by only a few hundred degrees, which cannot melt the sapphire and successfully separate from the crucible.

[0102] Finally, the obtained sapphire crystal 1 had the problem that the sapphire could not be taken out of the crucible. Even if it was forcibly removed, macro cracks would be generated on the surface of the sapphire.

[0103] Comparative Example 2

[0104] This comparative example is substantially the same as Example 1, except that:

[0105] The number of turns of the bottom coil 7 is increased to 39 turns. At this time, the turn density of the bottom coil 7 and the side coil 8 is close to 1:1.

[0106] Finally, the obtained sapphire crystal 1 had a significant melting problem at the bottom, with a melting depth of about 13 cm, which reduced the utilization rate of the sapphire. At the same time, the crystalline material remaining at the bottom of the crucible 2 after melting still needed to be removed before the crucible 2 could be reused.

[0107] Example 2

[0108] This embodiment illustrates a separation process of a sapphire crystal 1, which is specifically as follows:

[0109] The first step: Invert the molybdenum crucible 2 (crucible 2 diameter 440mm, height 450mm) with the sapphire crystal 1 (crystal 1 diameter 430mm height 280mm, weight 160Kg) grown by heat exchange method on a supporting platform 10 that can move up and down, that is, the top of the crucible 2 is facing down and the bottom of the crucible 2 is facing up.

[0110] Step 2: Slowly move the slide rail 11 upward, and move the support platform 10 fixedly connected to the slide rail 11 upward, and place the crucible 2 inside the induction coil, such as Figure 3 As shown, the size of the induction coil is a bottom diameter of 460 mm, a height of 350 mm, a diameter of the copper tube constituting the induction coil of 10 mm, a number of turns of the side coil 8 of 35, a number of turns of the bottom coil 7 of 23, and a gap between the bottom of the crucible 2 and the bottom of the induction coil is adjusted to be between 10 mm, and a gap between the side of the crucible 2 and the side of the coil is adjusted to be between 10 mm.

[0111] Step 3: The protective chamber 9 equipped with the induction coil and the crucible 2 is sealed and evacuated. The vacuum system is composed of a two-stage system of a mechanical pump 14 and a diffusion pump 15. The mechanical pump 14 is started to evacuate to 5 Pa, and then the diffusion pump 15 is started to evacuate to a high vacuum of 3×10 -3Pa, high-purity 99.99% nitrogen is filled into the protection chamber 9 through the charging valve 16, and the charging valve 16 is closed when the furnace pressure gauge 17 shows that the pressure in the furnace is positive and the pressure is 0.03Mpa. The purpose of filling nitrogen is to prevent the molybdenum crucible 2 from being oxidized due to the increase in temperature during the induction heating process.

[0112] Step 4: Open the water inlet of the induction coil, the water inlet temperature is 18 degrees, the flow rate is 8L / min, and the equipment power 12 is started. The induction coil can produce eddy currents in the crucible 2, and instantly heat the molybdenum material at the bottom and side of the crucible 2. The melting point of the sapphire crystal 1 is 2050°C. When the temperature of the molybdenum material reaches 2050°C, the sapphire crystal 1 adhered to the inner wall of the crucible 2 and the inner wall of the bottom of the crucible 2 will become a melt due to the heat rise. Under the action of gravity, the entire sapphire crystal 1 is separated from the molybdenum crucible 2 and lands on the supporting platform 10.

[0113] Step 5: Cut off the power supply 12, fill the furnace body with air at room temperature and pressure through the inflation valve 16 until the internal and external pressures are balanced, open the furnace body, slowly move the supporting platform 10 downward, and take out the complete sapphire crystal 1, weighing 160Kg.

[0114] Example 3

[0115] This embodiment illustrates a separation process of a sapphire crystal 1, which is specifically as follows:

[0116] The first step: Invert the molybdenum crucible 2 (crucible 2 diameter 500mm, height 450mm) with the doped titanium sapphire crystal 1 (crystal 1 diameter 490mm height 270mm, weight 202Kg) grown by heat exchange method on a supporting platform 10 that can move up and down, that is, the top of the crucible 2 is facing down and the bottom of the crucible 2 is facing up.

[0117] Step 2: Slowly move the slide rail 11 upward, and move the support platform 10 fixedly connected to the slide rail 11 upward, and place the crucible 2 inside the induction coil, such as Figure 3 As shown, the size of the induction coil is a bottom diameter of 520 mm, a height of 350 mm, a diameter of the copper tube constituting the induction coil of 15 mm, a number of turns of the side coil 8 of 24, a number of turns of the bottom coil 7 of 23, and a gap between the bottom of the crucible 2 and the bottom of the induction coil is adjusted to be between 10 mm, and a gap between the side of the crucible 2 and the side of the coil is adjusted to be between 10 mm.

[0118] Step 3: The protective chamber 9 equipped with the induction coil and the crucible 2 is closed and evacuated. The vacuum system is composed of a two-level system of a mechanical pump 14 and a diffusion pump 15. The mechanical pump 14 is started to evacuate to 5 Pa, and then the diffusion pump 15 is started to evacuate to a high vacuum of 2×10 -3Pa, high-purity 99.99% nitrogen is filled into the protection chamber 9 through the charging valve 16, and the charging valve 16 is closed when the furnace pressure gauge 17 shows that the pressure in the furnace is positive and the pressure is 0.05Mpa. The nitrogen is filled to prevent the molybdenum crucible 2 from being oxidized due to the increase in temperature during the induction heating process.

[0119] Step 4: Open the water inlet of the induction coil, the water inlet temperature is 20 degrees, the flow rate is 10L / min, start the equipment power 12, the induction coil can produce eddy currents in the crucible 2, and instantly heat the molybdenum material at the bottom and side of the crucible 2. The melting point of the doped titanium sapphire crystal 1 is 2050°C. When the temperature of the molybdenum material reaches 2050°C, the doped titanium sapphire crystal 1 adhered to the inner wall of the crucible 2 and the inner wall of the bottom of the crucible 2 will become a melt due to the heat rise. Under the action of gravity, the entire doped titanium sapphire crystal 1 is separated from the molybdenum crucible 2 and lands on the supporting platform 10.

[0120] Step 5: Cut off the power supply 12, fill the furnace body with air at room temperature and pressure through the inflation valve 16 until the internal and external pressures are balanced, open the furnace body, slowly move the supporting platform 10 downward, and take out the complete doped titanium sapphire crystal 1, weighing 202 kg.

[0121] In addition, the utility model also conducted the same separation tests on sapphire crystals prepared by various other methods, such as the crucible descent method, and other crystals prepared by the same heat treatment method, such as spinel and yttrium aluminum garnet, and achieved the same technical effects.

[0122] And for larger crystals, the difference in power density between the side and bottom surfaces also follows a similar pattern, except that different crystals 1 may correspond to different optimal ratios.

[0123] Based on the above embodiments and comparative examples, it can be clearly seen that the separation method provided in the embodiments of the utility model is a method for non-destructively separating crystals from crucibles by induction heating, which can achieve complete separation of crystal ingots and multiple recycling of crucibles, and can significantly reduce the cost of crucibles consumed when growing crystals such as sapphire, spinel and yttrium aluminum garnet by heat treatment methods such as heat exchange method, crucible descent method and temperature gradient method.

[0124] It should be understood that the above embodiments are only for illustrating the technical concept and features of the utility model, and their purpose is to enable people familiar with the technology to understand the content of the utility model and implement it accordingly, and they cannot be used to limit the protection scope of the utility model. Any equivalent changes or modifications made according to the spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. An induction heating coil for a device for separating a crystal from a crucible, wherein the crucible comprises a side wall and a bottom plate, wherein the crystal is bonded to the crucible before separation and is in direct contact with the bottom plate, wherein: The induction heating coil comprises a side coil and a bottom coil, the side coil is shaped like the side wall, the bottom coil is shaped like the bottom plate, and the accommodating space formed by the side coil and the bottom coil can accommodate the crucible in the shape of the crucible.

2. The induction heating coil according to claim 1, characterized in that: The side coil is of helical spring type and the bottom coil is of flat helical type.

3. The induction heating coil according to claim 2, characterized in that: The side coils and the bottom coil are connected in series.

4. The induction heating coil according to claim 3, characterized in that: The side coil and the bottom coil are an integrated coil structure formed by bending an integrated hollow metal tube.

5. The induction heating coil according to claim 4, characterized in that: A cooling medium inlet and a cooling medium outlet are respectively arranged at two ends of the hollow metal tubular object.

6. The induction heating coil according to claim 3, characterized in that: The turn density of the side coil is 1.5-2.5 times the turn density of the bottom coil.

7. A crystal and crucible separation device, used for separating a crystal and a crucible by induction heating, wherein the crystal is adhered to the inner wall of the crucible before separation; characterized in that: The separation device comprises: The induction heating coil according to any one of claims 1 to 6, wherein when induction heating is performed, the induction heating coil is arranged to surround and conform to the crucible; A bearing structure, used for bearing the crucible and the crystal inside the crucible during induction heating; and a high-frequency power supply unit, which is used to provide high-frequency alternating current to the induction heating coil to achieve the induction heating.

8. The separation device according to claim 7, characterized in that It also includes a protection chamber, in which the induction heating coil and the bearing structure are both arranged; The protective chamber can be evacuated and / or replaced with a protective atmosphere.

9. The separation device according to claim 7, characterized in that: The spacing between the side coil of the induction heating coil and the side wall of the crucible and the spacing between the bottom coil of the crucible and the bottom plate of the crucible are equal.

10. The separation device according to claim 7, characterized in that: The bearing structure comprises a horizontally arranged carrier, the crucible can be carried on the surface of the carrier, and the opening points to the direction of gravity.

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