Crystallization growth method, crystallization growth apparatus, and computer program

Abstract

A first raw material layer (4) and a second raw material layer (6) with different additive concentrations are prepared in a cooling copper container (2). The additive concentration of the first raw material layer (4) is set to be approximately the same as the concentration of the additive used for crystallization multiplied by the reciprocal of the effective segregation coefficient, and the additive concentration of the second raw material layer (6) is set to be approximately the same as the concentration of the additive used for crystallization. While the surrounding area is cooled by the cooling copper container (2), the first raw material layer (4) is melted by a high-frequency induction coil (1), thereby creating a double crucible for growing crystals (7). Furthermore, the high-frequency induction coil (1) is controlled to melt the second raw material layer (6) and supply molten liquid in response to the growth of the growing crystals (7). In addition, raw material is supplied to the first raw material layer (4) which decreases due to the growth of the growing crystals (7). By doing so, the additive concentration is maintained at approximately constant, and high-quality long crystals with excellent homogeneity are obtained in a low-cost manner.

Description

[Technical Field]

[0001] This invention relates to a crystal growth method, crystal growth apparatus, and program for growing crystals from a molten liquid without using a precious metal crucible, and particularly to a crystal growth method, crystal growth apparatus, and program for stably growing long strips of crystals in a high-quality manner. [Previous Technology]

[0002] Methods for growing large and high-quality single crystals have been known in the past, including the pull-up method, edge-defined film-fed growth (EFG), zone melting method, bubble growth method, top-seeded melt growth (TSMG), Britzmann method, vertical gradient solidification (VGF) method, and heat exchange method (HEM). These methods are suitable for growing large crystals with a mixed molten composition, and are called melt growth methods, which involve contacting the seed crystal with the molten liquid filling the crucible and using a temperature gradient to produce single crystals.

[0003] The above-mentioned melt growth method, whether for oxide single crystals or semiconductor single crystals, is currently the most commonly used method in industry. However, there is a problem that the homogeneity of the additive concentration is difficult to control, leading to a loss of homogeneity in the additive concentration.

[0004] Furthermore, in order to increase the ratio of crystals with approximately uniform additive concentration, improvements such as the double-crucible method are employed in the pull-up process (Patent Document 1 and Patent Document 2). However, the double-crucible method also has many problems, such as increased apparatus complexity, the need for multiple expensive precious metal crucibles, and the requirement for large precious metal crucibles to ensure the crystallization aperture. Therefore, a further improvement method is required. Previous Art Documents Patent Documents

[0005] Patent Document 1: Japanese Patent No. 2729243; Patent Document 2: Japanese Patent No. 3551242 [Summary of the Invention]

[0006] Problem to be Solved by the Invention The object of this invention is to provide a crystal growth method that can advantageously produce crystals with excellent homogeneity and high additive concentration in an industrial manner. Means for Solving the Problem

[0007] The following describes the means used to solve the above problems and their effects.

[0008] The crystal growth method of the present invention is characterized in that: while cooling the outer periphery of a raw material containing additives to below the melting point of the raw material, the raw material is directly heated by applying a high frequency to melt it, and crystals are grown from the molten raw material. In this crystal growth method, the raw material is composed of multiple layers with different concentrations of additives. Based on this configuration, by utilizing the segregation phenomenon, grown crystals reflecting different concentrations of additives in the multiple layers can be obtained in a low-cost manner.

[0009] In the aforementioned crystal growth method, the aforementioned multiple layers are characterized in that: the aforementioned multiple layers are composed of a first raw material layer and a second raw material layer that are adjacent to each other; the concentration of the additive in the aforementioned first raw material layer is approximately the same as the concentration of the additive in the aforementioned crystal multiplied by the reciprocal of the effective segregation coefficient; and the concentration of the additive in the aforementioned second raw material layer is approximately the same as the concentration of the additive in the aforementioned crystal. Based on this configuration, by means of segregation, crystals with an additive concentration having the additive concentration of the first layer multiplied by the effective segregation coefficient can be obtained, and approximately homogeneous growth crystals with the target additive concentration can be obtained.

[0010] In the aforementioned crystal growth method, the characteristic is that: while moving a high-frequency coil for applying the aforementioned high frequency relative to the first raw material layer towards the second raw material layer, crystal growth is performed, and the raw material is directly heated by the aforementioned high frequency, so that the raw material with a weight approximately the same as the weight of the crystal grown from the molten raw material melts. According to this configuration, the thermal environment at the solid-liquid interface can be kept consistently and approximately constant, and elongated crystals with approximately homogeneous target additive concentration and quality can be obtained.

[0011] In the aforementioned crystal growth method, the characteristic is that when the high-frequency coil moves relative to the aforementioned second raw material layer, the weight of the aforementioned second raw material layer melted per unit time is approximately the same as the weight of the aforementioned grown crystal per unit time.

[0012] In the aforementioned crystal growth method, the characteristic is that: the aforementioned raw material with an additive concentration approximately the same as that used in the crystal growth is added to the aforementioned melt. According to this configuration, since a balance can be maintained between the grown crystal and the additive concentration of the added raw material, it is possible to obtain elongated crystals with a target additive concentration and approximately homogeneous structure.

[0013] In the aforementioned crystal growth method, the characteristic is that the weight of the aforementioned raw material added per unit time is equal to the weight of the aforementioned grown crystal per unit time. Based on this configuration, since the weight balance between the grown crystal and the added raw material can be maintained, the liquid level can be kept approximately the same, and the thermal environment at the solid-liquid interface can be kept constant and approximately constant, thereby obtaining elongated crystals with the target additive concentration and approximately homogeneity.

[0014] In the aforementioned crystal growth method, the aforementioned additional raw material is characterized in that: the aforementioned additional raw material is a liquid, powder, granules, wire, rod, or granular. According to this configuration, even with raw materials of various forms, the liquid level can still be kept approximately the same, and the thermal environment at the solid-liquid interface can also be kept approximately the same, thus enabling the obtaining of elongated crystals with the target additive concentration and approximately homogeneity.

[0015] In the aforementioned crystal growth method, the additive is characterized as a luminescent center of a luminescent material. Based on this configuration, by using the luminescent center of the luminescent material as an additive, elongated luminescent material crystals with a target additive concentration and approximately homogeneous structure can be obtained.

[0016] In the aforementioned crystal growth method, the crystal is characterized as a scintillator crystal. Based on this configuration, the luminescent center of the scintillator material is used as an additive, thereby obtaining a long, elongated scintillator crystal with a target additive concentration and approximately homogeneous structure.

[0017] In the aforementioned crystal growth method, the crystal is characterized by being a laser crystal. Based on this configuration, since the additive is the luminescent center of the laser material, a long, approximately homogeneous laser crystal with the target additive concentration can be obtained.

[0018] In the aforementioned crystal growth method, the additive is characterized in that it is a donor or acceptor of a semiconductor material. According to this configuration, since the additive is a donor or acceptor of a semiconductor material, elongated semiconductor crystals with a target additive concentration and approximately homogeneous structure can be obtained.

[0019] Furthermore, the crystal growth apparatus of the present invention is characterized by comprising: a heating component for directly heating a raw material containing an additive by means of a high-frequency heating method; a cooling component for cooling the outer periphery of the raw material containing the additive to below the melting point of the raw material; a memory for storing information relating to the position of each of a plurality of layers of raw material with different concentrations of the additive; a control component for controlling the heating component to move according to the aforementioned position-related information, so that the raw material in one of the plurality of layers of raw material melts, and at least a portion of the raw material in the other layers melts; and a crystal holding component for holding crystals formed from the melted raw material. Based on this configuration, a crystal growth apparatus can be obtained, which can cultivate elongated crystals with a target additive concentration and substantially homogeneous structure by means of a control component, wherein the control component controls the concentration of the additive based on an effective segregation coefficient at the crystal interface of the crystal growth apparatus.

[0020] In the aforementioned crystal growth apparatus, the aforementioned one layer is a layer of the aforementioned raw material composed of an additive concentration determined based on the effective segregation coefficient at the interface between the aforementioned melt and the aforementioned crystal, and the aforementioned control component moves the aforementioned heating component to: initially melt all the aforementioned raw material in the aforementioned one layer, and then melt at least a portion of the aforementioned other layers.

[0021] In the aforementioned crystal growth apparatus, the aforementioned control component is further controlled to move the aforementioned crystal holding component in a direction separate from the aforementioned molten liquid, and to move the aforementioned heating component in parallel with the movement to melt at least a portion of the aforementioned raw material in the aforementioned other layers.

[0022] The aforementioned crystal growth apparatus includes a load cell, which measures the change in weight of the crystal held in the aforementioned crystal holding component. The aforementioned control component controls the movement of the aforementioned heating component used to melt the aforementioned other layers based on the change in weight measured by the aforementioned load cell.

[0023] The aforementioned crystal growth apparatus includes a supply unit, which is used to add the aforementioned raw material with an additive concentration that is approximately the same as that of the other layers.

[0024] The crystal growth apparatus described above is characterized by growing crystals by an upward pull method. According to this configuration, since there is an upward pull mechanism in the crystal growth apparatus, a crystal growth apparatus can be obtained in which crystals of approximately homogeneous quality and long strips can be cultivated in a generally homogeneous manner with a target additive concentration by an upward pull method.

[0025] The aforementioned crystal growth apparatus is characterized by growing crystals using the Britzmann process. Based on this configuration, since the Britzmann process can be employed in a portion of the crystal growth apparatus, a crystal growth apparatus can be obtained that can cultivate elongated crystals of approximately homogeneous concentration of the desired additive using the Britzmann process.

[0026] The aforementioned crystal growth apparatus is characterized by growing crystals using a vertical gradient solidification (VGF) method. Based on this configuration, since a VGF method can be employed in a portion of the crystal growth apparatus, a crystal growth apparatus can be obtained that can cultivate elongated crystals with a target additive concentration and approximately homogeneity using the VGF method.

[0027] The crystal growth apparatus described above is characterized by growing crystals by the bubbling method. According to this configuration, since the bubbling method can be used in a part of the crystal growth apparatus, a crystal growth apparatus can be obtained in which substantially homogeneous elongated crystals can be cultivated by the bubbling method at a target additive concentration.

[0028] The crystal growth apparatus described above is characterized by growing crystals by heat exchange method (HEM). According to this configuration, since a heat exchange method (HEM) mechanism can be used in a part of the crystal growth apparatus, a crystal growth apparatus can be obtained that can cultivate long strip crystals with a target additive concentration and substantially homogeneous structure by heat exchange method (HEM).

[0029] The aforementioned crystal growth apparatus is characterized by growing crystals using an edge-defined film-fed growth (EFG) method. Based on this configuration, since an EFG method can be employed in a portion of the crystal growth apparatus, a crystal growth apparatus can be obtained that can cultivate elongated crystals with a target additive concentration and substantially homogeneous structure using the EFG method.

[0030] The aforementioned crystal growth apparatus is characterized by growing crystals using a zone melting method. Based on this configuration, since a zone melting mechanism can be employed in a portion of the crystal growth apparatus, a crystal growth apparatus can be obtained that can cultivate elongated crystals with a target additive concentration and substantially homogeneous structure using a zone melting method.

[0031] Furthermore, the program of the present invention is a program for causing a computer to perform the following processing: in a crystal growth method that directly heats a raw material containing an additive by a high-frequency heating method to produce crystals from the melt of the aforementioned raw material, the concentration of the aforementioned additive is controlled based on the effective segregation coefficient at the interface between the aforementioned melt and the aforementioned crystals. According to this configuration, since a program is provided that controls the concentration of the aforementioned additive while simultaneously growing crystals in a crystal growth apparatus, it is possible to control the concentration of the target additive and cultivate substantially homogeneous elongated crystals. Effects of the Invention

[0032] According to the above, according to the present invention, a method, apparatus and process for manufacturing long strip crystals with a target additive concentration and substantially homogeneous structure can be provided in a low-cost manner.

Implementation Method

[0034] The following embodiments of the invention are described in more detail using drawings, but are not limited to these specific examples.

[0035] The crystal growth method of an embodiment of the present invention involves directly heating the raw material body by applying a high frequency while cooling the outer periphery of the raw material body containing additives to below the melting point of the raw material body, thereby melting the raw material body and growing crystals from the molten raw material body. In this crystal growth method, the raw material body is composed of multiple layers with different concentrations of additives. According to this crystal growth method, single crystals composed of, for example, the following raw materials can be obtained by crystal growth: zirconium oxide, titanium, titanium aluminum alloy, iron oxide, magnesium oxide, germanium oxide, calcium oxide, strontium oxide, yttrium oxide, chromium oxide, lanthanum chromium oxide, strontium titanate, cadmium oxide, scandium oxide, diurethane oxide, lanthanum nickel oxide, gallium oxide, aluminum oxide, magnesium aluminum oxide, yttrium aluminum garnet, gallium aluminum gallium garnet, lanthanum yttrium silicon oxide, strontium iodide, cerium bromide, lithium calcium aluminum fluoride, lithium yttrium oxide, and lithium niobate.

[0036] First, the crystal growth apparatus 10 of the present invention will be described with reference to FIG1. ​​The crystal growth apparatus 10 includes a water-cooled copper container 2, a high-frequency induction coil (high-frequency coil) 1 as a heating component, a holding rod (crystallization holding component) not shown, and a seed crystal 8 held in the holding rod (not shown). A raw material body, namely a first layer of sintered raw material body 4 and a second layer of sintered raw material body 6, is stacked in the water-cooled copper container 2. In addition, the raw material body refers to a raw material body formed by mixing raw materials and additives. In this embodiment, the concentration of additives for the raw materials is different in the first layer of raw material body 4 and the second layer of raw material body 6.

[0037] The first layer of sintered raw material 4 and the second layer of sintered raw material 6 are formed into, for example, cylindrical shapes along the shape of the water-cooled copper container 2. Furthermore, the upper surface side (the upper side of the paper in FIG1) of the first layer of sintered raw material 4 and the second layer of sintered raw material 6 is taken as one end side, and the lower surface side (the lower side of the paper in FIG1) of the ground side of the first layer of sintered raw material 4 and the second layer of sintered raw material 6 is taken as the other end side. Additionally, the first layer of sintered raw material 4 and the second layer of sintered raw material 6 do not necessarily have to be cylindrical; they can be stacked from one end side to the other end side, and can be of any shape.

[0038] The water-cooled copper container 2 is made of copper, which has excellent thermal conductivity and is inexpensive. Furthermore, the water-cooled copper container 2 is configured to allow cooling of part or all of its outer wall by a fluid containing water via a cooling mechanism not shown.

[0039] The high-frequency induction coil 1 is arranged around the water-cooled copper container 2. The high-frequency induction coil 1 is configured to move relative to the outer wall of the water-cooled copper container 2. More specifically, it can move from the upper end to the lower end (from the upper side to the lower side of the paper in FIG1) of the water-cooled copper container 2 while maintaining a constant distance from the outer wall of the water-cooled copper container 2. The high-frequency induction coil 1 is configured to heat (directly heat) the first layer of sintered raw material 4 and the second layer of sintered raw material 6 shown in FIG1 by high-frequency induction.

[0040] A retaining rod (not shown) holds a seed crystal 8. The retaining rod is configured to move in the vertical direction and to rotate at a predetermined speed during seeding.

[0041] Next, the crystal growth method of an embodiment of the present invention will be described with reference to FIG2. First, in the first step S101, while the surrounding area of ​​the first layer sintered raw material 4 and the second layer sintered raw material 6 is cooled below the melting point by means of the cooling function (cooling component) of the water-cooled copper container 2, the central part of one end side of the first layer sintered raw material 4 is heated and melted by means of the high-frequency induction coil 1. In addition, in the initial heating of the first layer sintered raw material 4, a metal or semiconductor that easily absorbs magnetic fields can be used. When such a metal or semiconductor is used in the metal element contained in the raw material, the contamination of unwanted impurities in the grown crystal can be reduced. By means of the heating of the high-frequency induction coil 1, when the first layer sintered raw material 4 becomes a molten liquid by means of the heating of the starter, the resistivity will drop significantly, the absorption of magnetic fields will be better, and thus a stable molten band 41 can be formed (see FIG3). The metal that rapidly transfers the first layer of sintered raw material 4 to the stable molten zone 41 (see Figure 3) is called an initiator. When the raw material of the sintered body is gallium oxide, Ga metal, for example, can be used. When (Lu, Y)2SiO5 (LYSO), Y3Al5O12 (YAG), and Y2O3 are used as raw materials, Y metal, for example, can be used. When LYSO and La-GPS are used as raw materials, Si semiconductor, for example, can be used. When LiTaO3 (LT) is used as raw material, Ta metal is used as the aforementioned initiator, and when LiNbO3 (LN) is used, Nb metal, for example, is used as the aforementioned initiator. Next, the high-frequency induction coil 1 is gradually moved to the other end, and after the first layer melts, one end of the second layer of sintered raw material 6 melts. In addition, the area around the first layer of sintered raw material 4 and the second layer of sintered raw material 6 is cooled below the melting point by the cooling function of the water-cooled copper container 2, thereby forming a sintered raw material support layer 3 that maintains the solid state.

[0042] Next, in step S102, the seed crystal 8 is brought into contact with the melt at the center of one end of the sintered raw material body 4 of the first layer. By heating with the high-frequency induction coil 1 as described above, the center of one end of the sintered raw material body 4 of the first layer becomes a melt of the raw material body, and one end of this melt is brought into contact with the seed crystal 8, which is set to the so-called seeding state (not shown).

[0043] Next, in step S103, while maintaining cooling around the raw material body, the heating position of the high-frequency induction coil 1 is moved from one end of the sintered raw material body 4 of the first layer to the other end, and the melting position of the raw material in the center of the sintered raw material body 4 of the first layer is moved from one end of the sintered raw material body 4 to the other end. By moving in this way, a growth crystal 7 reflecting the additive concentration of the effective segregation coefficient can be obtained from the position where the seed crystal 8 contacts the melt of the sintered raw material body 4 of the first layer, from one end of the sintered raw material body 4 to the other end. That is, the growth crystal 7 grows gradually and elongated as the high-frequency induction coil 1 descends. At this time, the growth crystal 7 can also be pulled in the direction separating from the melt at a predetermined speed. In addition, as a crystal growth mechanism, when using the Cz method, it is more ideal to perform an upward pull.

[0044] Alternatively, the holding rod (not shown) supporting the seed crystal 8 can be rotated. In this way, since the molten liquid of the first layer of sintered raw material 4 can be stirred, the temperature of the molten liquid of the first layer of sintered raw material 4 can be stabilized rapidly.

[0045] Here, at least in steps 2 S102 and 3 S103, the heating of the central portion of the sintered raw material body 4 of the first layer by the high-frequency induction coil 1 is carried out by setting the frequency of induction heating to a range deviating from the resonant frequency of the melt. By setting it to a range deviating from the resonant frequency, overheating can be avoided while the temperature gradient can be appropriately controlled. The depth of the magnetic field penetrating into the heated body depends on the frequency of induction heating. By cooling, the unmelted outer periphery is kept solid, and by appropriately setting and controlling the frequency, a state in which the temperature decreases relatively towards the center of the melt is formed in a plane perpendicular to the direction from one end of the raw material body to the other (temperature gradient of the melt). In this way, by varying the frequency of induction heating within a range deviating from the resonant frequency of the melt and controlling the temperature gradient of the melt in a plane, crystallization can be promoted and the diameter of the crystallized raw material can be controlled. Furthermore, such control is not necessarily required. It can also be a component that changes the position of the coil, a component that controls the pulling speed of the lever, or any other component, as long as it can generate a temperature gradient.

[0046] After the seed crystal 8 has been pulled up, the growth crystal 7 is separated from the melt, and heating is gradually stopped to allow the growth crystal 7 to solidify. Alternatively, after the growth crystal 7 has grown from the contact position with the seed crystal 8 to a predetermined position in the direction from one end to the other end of the first layer of sintered raw material body 4, the heating of the high-frequency induction coil 1 is stopped, and the melt inside the growth crystal 7 is slowly cooled and solidified. As a result, a single crystal of the growth crystal 7 raw material crystallized from the seed crystal 8 is formed inside the growth crystal 7. After slow cooling, the raw material (the first layer of sintered raw material body 4) surrounding the growth crystal 7 is removed, and the growth crystal 7 is taken out.

[0047] According to the above embodiment, the sintered raw material body 4 of the first layer and the sintered raw material body 6 of the second layer are cooled to below their melting point by a water-cooled copper container 2, thereby forming a sintered raw material body support layer 3 that maintains a solid state. The sintered raw material body support layer 3 can be regarded as a crucible containing the molten liquid of the sintered raw material body 4 of the first layer and the sintered raw material body 6 of the second layer. Generally speaking, when a crucible made of metal is heated, impurities will be secreted. It is known that these impurities will reduce the quality of the grown crystals. However, according to this embodiment, no contamination caused by impurities will be generated from the sintered raw material body support layer 3. In addition, since it is not necessary to use a precious metal crucible made of expensive materials, the manufacturing cost can be suppressed. Furthermore, while the high-frequency induction coil 1 is lowered from one end of the molten liquid of the sintered raw material body 4 of the first layer to the other end, the frequency of induction heating is appropriately controlled, thereby maintaining a state in which the temperature decreases towards the center of the grown crystal 7 in a plane perpendicular to the direction from one end of the grown crystal 7 to the other end. This allows for the production of higher quality crystals.

[0048] The seed crystal 7 is held at one end by a retaining rod (not shown). On the other hand, the other end is configured to contact the molten liquid 41 of the first layer shown in FIG3 during seeding.

[0049] As shown in Figure 1, the first layer of sintered raw material 4 and the second layer of sintered raw material 6, which are the basis for crystal formation, are disposed within the water-cooled copper container 2. More specifically, the second layer of sintered raw material 6 is disposed on the bottom side of the water-cooled copper container 2. The first layer of sintered raw material 4 is disposed on the upper side of the water-cooled copper container 2 and on the upper side of the second layer of sintered raw material 6. For example, when manufacturing Ce-added Gd3(Al,Ga)5O12 (Ce:GAGG) crystals, the raw materials for the first layer of sintered raw material 4 and the second layer of sintered raw material 6 can be powders such as Gd2O3, Al2O3, Ga2O3, and CeO2.

[0050] The first layer of sintered raw material 4 and the second layer of sintered raw material 6 are formed, for example, from compressed powder, and are constructed by adding different concentrations of additives to each layer for the same raw material. Furthermore, the raw material itself may differ in each layer. In this embodiment, the additive concentration of the first layer of sintered raw material 4 is higher than the additive concentration of the second layer of sintered raw material 6. For example, when manufacturing Ce-added Gd3(Al,Ga)5O12 (Ce:GAGG) crystals, cerium oxide (Gd2O3) can be used as the additive for the first layer of sintered raw material 4 and the second layer of sintered raw material 6.

[0051] The ratio of raw materials to additives in the first layer of sintered raw material body 4 is, for example, set as Ce:(Ce+Gd) = 2.98:100. This ratio is determined by considering the effective segregation coefficient at the interface between the molten liquid of the first layer of sintered raw material body 4 melted by the high-frequency induction coil 1 and the grown crystal 7. That is, the additive concentration of the first layer of sintered raw material body 4 is adjusted to be approximately the same as the concentration of the additive for the grown crystal 7 multiplied by the reciprocal of the effective segregation coefficient. In addition, other additives are weighed by stoichiometry and added appropriately as mixed additives.

[0052] Similarly, the ratio of raw materials to additives in the sintered raw material body 6 of the second layer is, for example, set as Ce:(Ce+Gd) = 1:100. The additive concentration in the sintered raw material body 4 of the second layer is adjusted to be approximately the same as the additive concentration in the crystallization. In addition, other additives are weighed by stoichiometry and added appropriately as mixed additives.

[0053] Furthermore, while the term "approximately the same" is generally adjusted to ±0.001%, it can also be outside this range. The important thing is that the deviation in the concentration of the additives in the crystallization falls within a certain range to meet the required specifications. Therefore, the proportion of additives in the first layer is appropriately determined based on the segregation phenomenon. In this way, approximately homogeneous crystals that meet the required specifications can be obtained.

[0054] Here, although the concentration of additives in the sintering raw material body of the second layer is set to be approximately the same as the concentration of additives in the crystallization, it is not limited to this, and can also be set to be determined based on the effective segregation coefficient.

[0055] As shown in Figure 3, the first layer of sintered raw material body 4 and the second layer of sintered raw material body 6, with the raw material and additive concentrations adjusted as described above, become molten liquid when heated by the high-frequency induction coil 1, forming a layer composed of the first layer of molten liquid 41 and a layer composed of the second layer of molten liquid 51. However, for ease of explanation, although the first layer of molten liquid 41 and the second layer of molten liquid 51 are clearly illustrated separately, the second molten liquid 51 generated by melting one end of the second sintered raw material body 6 mixes with the first molten liquid 41 during melting, and therefore is not clearly separated into molten liquid layers. In Figure 3, the second melt zone temporarily generated when the second sintered raw material body 6 is continuously melted in accordance with the crystal growth rate is illustrated as molten liquid 51.

[0056] Next, using the crystallization method and apparatus of this embodiment, a control method for crystal growth will be described.

[0057] In step S103 shown in FIG2, as the growth of the crystallization 7 occurs, the high-frequency induction coil 1 is moved from one end of the melt 41 of the first layer shown in FIG3 to the other end. At this time, in step S103, as shown in FIG4, control from step S201 to step S202 is performed. Steps S201 to S202 are repeatedly performed during the growth of the crystallization 7, which reflects the effective segregation coefficient at the interface between the melt and the crystallization.

[0058] As shown in Figure 4, in step S201, when the growth of the growth crystal 7, which reflects the concentration of additives reflecting the effective segregation coefficient, begins, a load cell (not shown) begins to measure the weight WC of the growth crystal 7 precipitated from the seed crystal 8. The increase in weight ΔWC of the growth crystal 7 is stored as the weight change per unit time and then converted into the volume change ΔVC of the growth crystal 7 per unit time using Equation (1), and stored in the control unit (control component) (not shown). In addition, the individual density ρC of the growth crystal 7 is a known value determined according to each arbitrarily selected raw material, and is stored in advance in the control unit. Furthermore, the volume change ΔVC is equivalent to the volume reduction ΔVmelt2 of the melt formed by mixing the melt 41 of the first layer and the melt 51 of the second layer shown in Figure 3 [Equation (2)]. That is, as the volume increases due to the growth of the growth crystal 7, the volumes of the melt 41 of the first layer and the melt 51 of the second layer decrease.

[0059] [Mathematical Expression 1]

[0060] Here, the control unit (not shown) is controlled to move the high-frequency induction coil 1 to one end of the sintered raw material 6 of the second layer, which is located on the other side of the molten liquid 51 of the second layer. That is, the high-frequency induction coil 1 is controlled to descend relative to the water-cooled copper container 2 to heat one end of the sintered raw material 6 of the second layer and melt a portion of it. In this way, a portion of the molten sintered raw material 6 of the second layer is supplied to the molten liquid 51 of the second layer by a reduced volume ΔVmelt2, so that the total volume of the molten liquid 41 of the first layer and the molten liquid 51 of the second layer does not change.

[0061] This control is achieved by controlling the moving speed of the high-frequency induction coil 1 as shown in Equation (3) through a control unit not shown. Here, D represents the inner diameter of the water-cooled copper container 2, Vcoil represents the moving speed of the high-frequency induction coil 1, Wt1 and Wt2 represent the weight of the grown crystal 7 in a predetermined time, and Δt represents time. That is, the moving speed of the high-frequency induction coil 1 is controlled such that the weight increase per unit time due to the growth of the grown crystal 7 ((Wt1-Wt2) / Δt) is equal to the area of ​​the water-cooled copper container 2 (π / 4×D2) multiplied by the amount of movement of the high-frequency induction coil 1 per unit time (Vcoil×Δt) and the value of density ρC (the weight reduction of the molten liquid mixed in the first and second layers). In addition, in practice, as mentioned above, the weight is converted into volume and calculated as shown in Equation (4). That is, the moving speed of the high-frequency induction coil 1 is controlled such that the volume of the molten liquid (ΔVmelt2) to be supplied to the molten liquid 51 of the second layer is equal to the volume calculated by multiplying the area of ​​the water-cooled copper container 2 (π / 4×D2) by the amount of movement of the high-frequency induction coil 1 per unit time (Vcoil×Δt).

[0062] [Mathematical Expression 2]

[0063] The control unit (not shown) is equipped with a computer program that executes the control sequence described above, and performs output control, descent speed control, and raw material supply control of the high-frequency induction coil 1 based on the input signal from the load cell (not shown). Furthermore, the control unit (not shown) is configured to display the volume of the molten second layer of sintered raw material 6 on a display unit (not shown), and instruct the supply of raw material with an additive concentration approximately the same as that of the second layer of sintered raw material 6 to the second layer of sintered raw material 6, or is equipped with a supply unit (not shown) that directly supplies raw material to the second layer of sintered raw material 6.

[0064] Next, the phenomena occurring in the molten liquid 41 of the first layer and the molten liquid 51 of the second layer will be explained.

[0065] As shown in Figure 3, when heated by the high-frequency induction coil 1, the water-cooled copper container 2 is formed in the order of the second layer of sintered raw material 6, the second layer of molten liquid 51, and the first layer of molten liquid 41 from the bottom side.

[0066] Figure 5 shows the state diagram of each raw material in Figure 3. The solid phase region shown in Figure 5 is the state of crystal 7 in Figure 3, maintaining its individual state. The liquid phase region refers to the state where the raw material becomes a molten liquid due to heating, and specifically the states of the first layer molten liquid 41 and the second layer molten liquid 51. Furthermore, the solid phase region and the liquid phase region are coexisting regions where solid and liquid phases coexist, such as the state between the growing crystal 7 and the first layer molten liquid 41 shown in Figure 3. Here, in this embodiment, the additive concentrations of the first layer molten liquid 41 and the second layer molten liquid 51 are adjusted to be different. In the crystal 7 and the first layer molten liquid 41, since the solid solubility is different in the solid phase and the liquid phase, segregation occurs.

[0067] Here, as shown in Figure 5, it is known that at the same temperature (e.g., TX), the concentration of B in the liquid phase, BL1, is higher than the concentration of B in the solid phase, BS1 (more concentrated than BS1). When the crystals of BS1 (solid phase) are pulled up from the melt, the concentration of B in the melt, BL1, changes along the liquidus line to BL2 (becomes more concentrated). The concentration of B in the solid phase obtained at BL2 is BS2 (more concentrated than BS1). In this way, since the concentration of B in the solid phase continues to change along the solidus line, the problem of inconsistent additive concentration arises.

[0068] In view of solving such problems, a double crucible consisting of an inner crucible and an outer crucible, as shown in FIG. 6, has been conventionally used. Specifically, the inner crucible is filled with molten raw material at an additive concentration of BL, and the outer crucible is filled with molten raw material at an additive concentration of BS. Furthermore, the inner crucible is provided with a plurality of connecting holes that communicate with the outer crucible. In this configuration, when crystal growth occurs, control is implemented as follows: That is, the raw material at an additive concentration of BS is resupplyed from the outside to the outer crucible to maintain a weight balance between the weight of the grown crystal at an additive concentration of BS pulled outside the system (outside the crucible) and the weight of the crystallized crystal at an additive concentration of BS supplied from the outer crucible to the grown crystal through the connecting holes provided in the inner crucible. By controlling in this way, the additive concentration BL of the molten material in the inner crucible is maintained at a constant, and the additive concentration BS in the solid phase crystallized therefrom is also maintained at a constant. However, the double crucible method has problems such as requiring the use of two crucibles, and the high cost when both the inner and outer crucibles are made of precious metals.

[0069] Here, in this embodiment, the molten liquid 41 of the first layer is regarded as the concentration in the inner crucible, and the molten liquid 51 of the second layer is regarded as the concentration in the outer crucible, so as to control the growth of the crystal growth 7. According to the configuration of this embodiment, the same function as a double crucible is achieved by using the simple configuration of the water-cooled copper container 2 and the sintered raw material support layer 3 shown in the stacking diagram 3, as well as the sintered raw material 4 of the first layer and the sintered raw material 6 of the second layer. The sintered raw material support layer 3 is equivalent to the outer wall of the inner crucible in the double crucible, and the part of the sintered raw material of the second layer that is appropriately melted at one end and supplied to the first melt zone in the state of molten liquid is equivalent to the function of the connecting hole of the inner crucible in the double crucible. Then, as the crystal growth 7 grows, in order to supply the molten liquid 51 of the second layer, the high-frequency induction coil 1 is controlled to descend so that the sintered raw material 6 of the second layer melts. In addition, according to this configuration, unlike the conventional double crucible, only a part of the sintered body of the second layer needs to be appropriately melted, so it also has a greater effect from the point of view of energy consumption.

[0070] Furthermore, similar to the conventional double crucible method shown in Figure 6, by continuously supplying raw materials with an additive concentration of BS in conjunction with the growth of the growth crystal 7, the additive concentration BL of the first layer of molten liquid 41 can be maintained at a constant level, thereby enabling the production of elongated growth crystals 7. While the method of continuously supplying raw materials with an additive concentration of BS can involve feeding them from the upper part of one end side (liquid surface) of the first layer of molten liquid 41, it is not limited to this. For example, a connecting hole communicating with the outside can be provided in a part of the water-cooled copper container 2, and the raw materials can be supplied through the connecting hole. The connecting hole can also be appropriately provided on the side of the water-cooled copper container 2, or appropriately provided at the bottom. Furthermore, the form of the raw materials with an additive concentration of BS can be, for example, liquid, powder, granules, wire, rod, or pellet.

[0071] In addition, although crystal growth methods like this can be locally applied, such as the up-pulling method, the Britzmann method, the vertical gradient solidification (VGF) method, the bubble growth method, the heat exchange method (HEM), the edge-defined film-fed growth (EFG) method, and the zone melting method, they are not limited to these methods and various methods can be applied.

[0072] Furthermore, although this embodiment describes the sequence of melting the second layer of sintered raw material 6 after melting the first layer of sintered raw material 4, it is also possible to simultaneously melt a portion of the first layer of sintered raw material 4 and a portion of the second layer of sintered raw material 6 at the same time point as the initial melting of the first layer of sintered raw material 4. As long as the size of the high-frequency induction coil 1 includes the thickness of the first layer of sintered raw material 4, melting can be performed simultaneously. After this, the second layer of sintered raw material 6 is appropriately melted, similar to this embodiment.

[0073] Furthermore, when a manufacturing method is adopted in which the grown crystal 7 is pulled in a direction separate from the molten liquid at a predetermined speed, the melting of the second layer of sintered raw material 6 is controlled to be appropriate in parallel with this upward pulling. In this way, the volume of the molten liquid layer formed by mixing the first layer of molten liquid 41 and the second layer of molten liquid 51 can be kept constant.

[0074] Furthermore, in this embodiment, although it is described that the layers are deposited in the order of the first sintered raw material and the second sintered raw material from one end to the other, depending on the value of the segregation coefficient, it is also possible to deposit them in the order of the second sintered raw material and the first sintered raw material. In this case, the melting order will not change. After the first molten liquid layer 41 is formed by controlling the position of the high-frequency induction coil 1, the second sintered body is gradually melted to form the second molten liquid layer 51 in sequence. In this case, since the second sintered body is located at the top, additional raw materials can be easily supplied from the supply section not shown in the figure, which simplifies the structure of the device.

[0075] Furthermore, in this embodiment, although the volume of the melt layer formed by mixing the first layer of melt 41 and the second layer of melt 51 is controlled to be constant, it is not limited to this, and other components can be used. As long as the concentration of additives in the melt layer formed by mixing the first layer of melt 41 and the second layer of melt 51 is maintained at least constant, the concentration of additives in the grown crystals can be set to constant. Thus, for example, when the volume of the mixed melt layer is allowed to gradually decrease, the concentration of additives in the second sintered body can be set to be thinner than the concentration of crystals, and the volume of the additional molten second sintered body can be controlled to be less than the increase in the volume of the grown crystals. In this case, since the mixed melt gradually decreases, it is worse than this embodiment from the viewpoint of manufacturing continuity, but since the amount of melting of the second sintered body can be reduced during crystal growth, the power consumption used for melting can be suppressed.

[0076] Furthermore, not only can the amount of additive be pre-configured based on the segregation phenomenon, but it can also be adjusted and controlled in real time within the manufacturing apparatus. For example, storage units for raw materials and additives (not shown) are provided separately. When the required additive concentration in crystallization is input from the display unit, the amount of additive mixed in the first sintering raw material body is determined according to that value and the effective segregation coefficient, and mixing control is performed.

[0077] Next, examples will be used to illustrate the topic in more detail.

[0078] [Example 1] First, Ce:GAGG crystal growth was performed in advance using the pull-up method with a common precious metal crucible. Based on the data of Ce concentration distribution in the growth direction evaluated by composition analysis, it was confirmed that when Ce contains 1% molar ratio of Ce at the Gd site during the pull-up crystal growth, the effective segregation coefficient of Ce is 0.336.

[0079] Next, the manufacture of Ce:GAGG crystals will be described as Example 1. First, considering the effective segregation coefficient (0.336) of Ce at the interface between the GAGG melt and the crystals, the concentration of the additive (Ce) in the raw material powder is divided into two raw material layers: a first raw material layer and a second raw material layer. That is, the additive concentration of the first raw material layer is set such that the Ce ratio is the reciprocal of the effective segregation coefficient (1 / 0.336 ≒ 2.98) as Ce:(Ce + Gd) = 2.98:100, and other components are weighed and mixed according to stoichiometry. The additive concentration of the second raw material layer is set such that the Ce ratio is approximately the same as the effective segregation coefficient as Ce:(Ce + Gd) = 1:100, and other components are weighed and mixed according to stoichiometry. In this example, pressed powder is used for the second raw material layer.

[0080] The prepared raw materials were filled into a water-cooled copper basket, and a molten raw material liquid was prepared by high-frequency heating using the first raw material layer. The seed crystal was a 3mm × 3mm × 50mm long GAGG single crystal cut along the b-axis. The growth conditions were set to a crystallization rotation speed of 5 rpm, an upward pull speed of 0.5~1mm / h, and an atmospheric atmosphere. As the crystal grew, the molten liquid reached the second raw material layer, and crystallization continued while dissolving the raw material in the second raw material layer. The crystal obtained in this way is referred to as Example 1.

[0081] The distribution of Ce concentration along the growth direction of the obtained crystals is shown in Figure 7A. The vertical axis represents the additive concentration, and the horizontal axis represents the crystallization rate. The crystallization rate is the value obtained by dividing the weight of the grown crystals at a certain time point, measured based on the input signal of a gravimeter (not shown), by the total weight of the sintered raw material body 4 of the first layer and the sintered raw material body 6 of the second layer. As shown in Figure 7A, the Ce concentration is low in the initial stage when the crystallization rate is low, and then the Ce concentration gradually increases and stabilizes to form a roughly uniform additive concentration.

[0082] Next, Ce:GAGG crystals were prepared in the same manner as in Example 1, except that the raw material layer was not distinguished. The crystals obtained in this way are designated as Comparative Example 1.

[0083] The distribution of Ce concentration along the growth direction of the obtained crystals is shown in Figure 7B. As shown in Figure 7B, the Ce concentration is low in the initial stage when the crystallization rate is low, and then the Ce concentration gradually increases, resulting in a state where it is impossible to obtain a roughly uniform additive concentration.

[0084] As shown in Figures 7A and 7B, from the results of Example 1 and Comparative Example 1, it can be confirmed that by setting the first raw material layer and the second raw material layer, the ratio of crystals with approximately uniform additive concentration can be increased for the additive concentration in the crystallization.

[0085] [Example 2] Next, the fabrication of Ce-added (La, Gd)2Si2O7 (Ce:La-GPS) crystals will be described as Example 2. First, similar to Example 1, Ce:La-GPS crystals were grown using a pull-up method with a conventional noble metal crucible. Based on data from compositional analysis to evaluate the Ce concentration distribution along the growth direction, it was confirmed that the effective segregation factor of Ce was 1.02 when 1% molar of Ce was present at the Gd sites during the pull-up crystal growth.

[0086] Commercially available high-purity Gd₂O₃, La₂O₃, SiO₂, and CeO₂ (each with a purity of 99.999%) raw material powders are prepared. Considering the effective segregation coefficient at the interface (1.02), the concentration of the additive (Ce) in the raw material powders is divided into two raw material layers: a first raw material layer and a second raw material layer. Specifically, the additive concentration of the first raw material layer is set such that the Ce ratio is the reciprocal of the effective segregation coefficient (1 / 1.02 ≈ 0.980) as Ce:(Ce + La + Gd) = 0.980:100, and other components are weighed and mixed according to stoichiometric methods. The additive concentration of the second raw material layer is set such that the Ce ratio is approximately the same as the effective segregation coefficient as Ce:(Ce + La + Gd) = 1:100, and other components are weighed and mixed according to stoichiometric methods. Furthermore, in this embodiment, pressed powder is used for the second raw material layer.

[0087] The prepared raw materials were filled into a water-cooled copper basket, and the first raw material layer was used to create a molten raw material liquid by high-frequency heating. The seed crystal was a 3mm × 3mm × 50mm long La-GPS single crystal cut along the b-axis. The growth conditions were set to a crystallization rotation speed of 5 rpm, an upward pull speed of 0.5~1mm / h, and an atmospheric atmosphere. As the crystal grew, the molten liquid reached the second raw material layer, and crystallization continued while dissolving the raw materials in the second raw material layer. The crystal obtained in this way is referred to as Example 2.

[0088] The distribution of Ce concentration along the growth direction of the obtained crystals is shown in Figure 7A. As shown in Figure 7A, the Ce concentration is high in the initial stage when the crystallization rate is low, and then the Ce concentration gradually decreases and stabilizes to form a roughly uniform additive concentration.

[0089] Next, Ce:La-GPS crystals were prepared in the same manner as in Example 2, except that the raw material layer was not distinguished. The crystals obtained in this way are designated as Comparative Example 2.

[0090] The distribution of Ce concentration along the growth direction of the obtained crystals is shown in Figure 7B. As shown in Figure 7B, the Ce concentration is high in the initial stage when the crystallization rate is low, and then the Ce concentration gradually decreases, resulting in a state where it is impossible to obtain a roughly uniform additive concentration.

[0091] As shown in Figures 7A and 7B, the results of Example 2 and Comparative Example 2 confirm that by setting the first raw material layer and the second raw material layer, the crystallization rate with a substantially uniform additive concentration can be increased, depending on the additive concentration during crystallization. [Example 3]

[0092] Next, the fabrication of Nd-added Y3Al5O12 (Nd:YAG) crystals will be described as Example 3. First, similar to Example 1, Nd:YAG crystal growth was performed beforehand using a conventional noble metal crucible pull method. Based on data from compositional analysis to evaluate the Nd concentration distribution along the growth direction, it was confirmed that during pull-method crystal growth, when 1% molar Nd was present at the Y site, the effective segregation coefficient of Ce was 0.18.

[0093] Commercially available high-purity Y₂O₃, Al₂O₃, and Nd₂O₃ (each with a purity of 99.999%) raw material powders are prepared. Considering the effective segregation coefficient (0.18) at the interface, the concentration of the additive (Nd) in the raw material powders is divided into two raw material layers: a first raw material layer and a second raw material layer. Specifically, the additive concentration of the first raw material layer is set such that the Nd ratio is the reciprocal of the effective segregation coefficient (1 / 0.18 ≒ 5.56) as Nd:(Nd+Y) = 5.56:100, and other components are weighed and mixed according to stoichiometric methods. The additive concentration of the second raw material layer is set such that the Ce ratio is approximately the same as the effective segregation coefficient as Nd:(Nd+Y) = 1:100, and other components are weighed and mixed according to stoichiometric methods. Furthermore, in this embodiment, pressed powder is used for the second raw material layer.

[0094] The prepared raw materials were filled into a water-cooled copper basket, and the first raw material layer was used to create a molten raw material liquid by high-frequency heating. The seed crystal was a 3mm × 3mm × 50mm YAG single crystal cut along the b-axis. The growth conditions were set to a crystallization rotation speed of 5 rpm, an upward pull speed of 0.5~1mm / h, and an atmospheric atmosphere. As the crystal grew, the molten liquid reached the second raw material layer, and crystallization continued while dissolving the raw materials in the second raw material layer. The crystal obtained in this way is referred to as Example 3.

[0095] The distribution of Nd concentration along the growth direction of the obtained crystals is shown in Figure 7A. As shown in Figure 7A, the Nd concentration is low in the initial stage when the crystallization rate is low, and then the Nd concentration gradually increases and gradually stabilizes to form a roughly uniform additive concentration.

[0096] Next, Nd:YAG crystals were prepared in the same manner as in Example 3, except that the raw material layer was not distinguished. The crystals obtained in this way are designated as Comparative Example 3.

[0097] The distribution of Nd concentration along the growth direction of the obtained crystals is shown in Figure 7B. As shown in Figure 7B, the Nd concentration is low in the initial stage when the crystallization rate is low, and then the Nd concentration gradually increases, resulting in a state where it is impossible to obtain a roughly uniform additive concentration.

[0098] As shown in Figures 7A and 7B, the results of Example 3 and Comparative Example 3 confirm that by setting the first raw material layer and the second raw material layer, the crystallization rate with a generally uniform additive concentration can be increased for the additive concentration in crystallization.

[0099] Examples of crystals for which such additives are controlled include Ce with Gd3(Ga,Al)5O12 (Ce: GAGG, preferably C&A), Ce with Lu2SiO5 (Ce: LSO, preferably Crystal Photonics, Inc.), and Ce with (Lu,Y)SiO5 (Ce: LYSO, preferably Crystal Photonics, Inc.). Inc.), Ce with added (Lu, Gd)2SiO5 (Ce: LGSO, ideally (for example) OXIDE), Tl: CsI, Tl: NaI, CeBr3, Ce: LaBr3, Tb3Ga5O12 (ideally (for example) OXIDE), Ce: LiCAF (ideally (for example) C&A), Eu with added LiCalAlF6 (Eu: LiCAF, ideally (for example) C&A), Ce with added LiSrAlF6 (Ce: LiSAF, ideally (for example) C&A), Eu with added L iSrAlF6 (Eu:LiSAF, ideally manufactured by C&A), Mg with added LiTaO3 (ideally manufactured by Sanju Ceramics), Mg with added LiNbO3 (ideally manufactured by Sanju Ceramics), sapphire, Nd with added Y3Al5O12 (Nd:YAG), Nd with added Lu3Al5O12 (Nd:LuAG), Yb with added Y3Al5O12 (Yb:YAG), Yb with added Lu3Al5O12 (Yb:LuAG), Ga2O3 (ideally manufactured by Novel Crystal Technology), REAlO3, REVO4 (RE = rare earth element), gallium oxide, silicon, alloys (ideally Ruscaloy(R) manufactured by C&A), iridium, etc., but the crystals targeted are not limited to these.

[0100] Furthermore, when the additive is a luminescent center of a luminescent material, a long strip of scintillator crystal or laser crystal with a target additive concentration and approximately homogeneous texture can be obtained. Also, when the additive is an donor or acceptor of a semiconductor material, a long strip of semiconductor crystal with a target additive concentration and approximately homogeneous texture can be obtained.

[0101] In this embodiment, the melting heating is performed by moving a high-frequency induction coil based on information related to the position of the first sintering raw material or the second sintering raw material. For example, a setting component may be provided on a display unit (not shown), which may set the thickness of each of the first and second sintering raw materials deposited in the crystal growth direction, and the initial position information of at least one of the first or second sintering raw materials. Alternatively, the position information of each of the first and second sintering raw materials may be preset and memorized. These values ​​are stored in a memory (not shown), and the movement of the high-frequency induction coil 1 described in this embodiment is controlled based on these values. Furthermore, it is not limited to this; it may also be configured to obtain position information by using a sensor that detects the position of the first or second sintering raw material, or it may be configured to obtain predetermined position information by receiving data from an external computer or the like.

[0102] Alternatively, based on the premise of using a sintered raw material of a predetermined size, the movement of the high-frequency induction coil can be controlled to a fixed amount each time. In this case, since the fixed amount of movement reflects the position value of each layer, this is equivalent to position-related information. Furthermore, the place where the program recording this fixed amount is stored is equivalent to memory. In any case, since the movement of the high-frequency induction coil can be appropriately controlled by the control unit as long as the positions of the first and second layers can be determined, the component for acquiring position-related information can also be any other component.

[0103] In this embodiment, although it is set as two layers, namely the first sintered body layer and the second sintered body layer, it is not limited to this, and three or more layers, such as the third sintered body layer, may also be set. It is conceivable that the concentration of additives is gradually reduced in each layer, so as to effectively utilize the raw material until the end without waste.

[0104] As explained above, according to an embodiment of the present invention, since the raw material is composed of multiple layers with different concentrations, a crystal growth method can be provided that can advantageously produce crystals with excellent homogeneity in terms of additive concentration in an industrial setting. Furthermore, in conventional melt growth methods, batch production is carried out during a period when the crystallization rate is low before characteristic inconsistencies occur, thus ending the crystallization process. This method can lead to a decrease in yield. In the present invention, it has been confirmed that even with a high crystallization rate, characteristic inconsistencies do not occur, thereby improving the yield. Moreover, since crystal growth can be performed continuously rather than in batch production, it is a method advantageous for industrial mass production.

[0105] Furthermore, the present invention is not limited to the embodiments described above. It is obvious that, within the technical concept of the present invention, various modifications and combinations can be implemented by those skilled in the art. [Simplified Explanation of the Diagram]

[0033] Figure 1 is a structural diagram showing the configuration of the crystallization growth apparatus. Figure 2 is a flowchart illustrating the crystallization growth method. Figure 3 is a structural diagram showing the configuration of the crystallization growth apparatus. Figure 4 is a flowchart illustrating the crystallization growth method. Figure 5 is a state diagram showing the state of each raw material layer after undergoing a thermal process. Figure 6 is a graph showing the relationship between the concentration of additives in the solid phase and the crystallization rate. Figure 7A is a graph showing the relationship between the concentration of additives and the crystallization rate in Examples 1, 2, and 3. Figure 7B is a graph showing the relationship between the concentration of additives and the crystallization rate in Comparative Examples 1, 2, and 3.

Claims

1. A crystal growth method comprising directly heating the raw material by applying a high frequency to the raw material while cooling the outer periphery of the raw material containing additives to below the melting point of the raw material, thereby melting the raw material and growing crystals from the melt of the raw material, wherein the raw material is composed of a first raw material layer and a second raw material layer with different additive concentrations, the additive concentration of the first raw material layer being approximately the same as the additive concentration of the crystallization layer multiplied by the reciprocal of the effective segregation coefficient, and the additive concentration of the second raw material layer being approximately the same as the additive concentration of the crystallization layer, wherein crystal growth is performed by moving a high-frequency coil for applying the high frequency relative to the first raw material layer towards the second raw material layer, thereby melting the raw material by directly heating the raw material by the high frequency, such that the weight of the raw material is approximately the same as the weight of the crystals grown from the melt of the raw material.

2. The crystal growth method of claim 1, wherein when the high-frequency coil moves relative to the aforementioned second raw material layer, the weight of the aforementioned second raw material layer melted per unit time is approximately the same as the weight of the aforementioned grown crystal per unit time.

3. The crystal growth method of claim 1 or 2, wherein the aforementioned raw material is added to the aforementioned melt at a concentration approximately the same as the concentration of the additives used in the aforementioned crystallization.

4. The crystal growth method of claim 3, wherein the weight of the aforementioned raw material added per unit time is equal to the weight of the aforementioned crystals grown per unit time.

5. The crystal growth method as described in claim 4, wherein the additional raw material is a liquid, powder, granules, wire, rod, or granules.

6. The crystal growth method as described in claim 5, wherein the additive of the aforementioned raw material is the luminescent center of the luminescent material.

7. The crystal growth method as described in claim 6, wherein the aforementioned crystal is a scintillator crystal.

8. The crystal growth method as described in claim 6, wherein the aforementioned crystal is laser crystallization.

9. The crystal growth method of claim 5, wherein the aforementioned additive is an donor or acceptor of a semiconductor material.

10. A crystal growth apparatus comprising: a heating component for directly heating a raw material containing an additive by a high-frequency heating method; a cooling component for cooling the outer periphery of the raw material containing the additive to below the melting point of the raw material; a memory for storing position-related information of a first raw material layer and a second raw material layer having different concentrations of the additive in the raw material; a control component for controlling the heating component to move according to the position-related information, such that the raw material in the first raw material layer melts, and at least a portion of the raw material in the second raw material layer melts; and a crystal holding component for holding crystals formed from the molten raw material, wherein the additive concentration in the first raw material layer is approximately the same as the additive concentration of the crystallized material multiplied by the reciprocal of the effective segregation coefficient, and the additive concentration in the second raw material layer is approximately the same as the additive concentration of the crystallized material. The aforementioned control component moves the aforementioned heating component relative to the aforementioned first raw material layer in the direction of the aforementioned second raw material layer, so that the aforementioned raw material with a weight approximately the same as the weight of the crystals grown from the molten raw material melts.

11. The crystal growth apparatus of claim 10, wherein the aforementioned control component moves the aforementioned heating component to: initially melt all the aforementioned raw material in the aforementioned first raw material layer, and then melt at least a portion of the aforementioned second raw material layer.

12. The crystal growth apparatus of claim 10, wherein the aforementioned control component is further controlled to move the aforementioned crystal holding component in a direction separate from the aforementioned melt, and to move the aforementioned heating component in parallel with the movement to melt at least a portion of the aforementioned raw material of the aforementioned second raw material layer.

13. The crystal growth apparatus of claim 10 further includes a load cell, which measures the change in weight of the crystal held in the crystal holding assembly, and the control assembly controls the movement of the heating assembly used to melt the second raw material layer based on the change in weight measured by the load cell.

14. The crystal growth apparatus of claim 10 further includes a supply unit for adding the aforementioned raw material at a concentration of additives substantially the same as that of the aforementioned second raw material layer.

15. The crystal growth apparatus of any of claims 10 to 14, wherein the crystal is grown by any of the following methods: pull-up method, Britzmann method, vertical gradient solidification (VGF), bubble growth method, heat exchange method (HEM), edge-defined film-fed growth (EFG), and zone melting method.

16. A computer program that causes a computer to perform the following processing: in a crystal growth method whereby the outer periphery of a raw material containing an additive is cooled to below the melting point of the raw material, and a high frequency is applied to the raw material to directly heat the raw material, thereby melting the raw material and growing crystals from the molten raw material, the concentration of the additive is controlled based on an effective segregation coefficient at the interface between the molten liquid and the crystals, wherein the raw material is composed of a first raw material layer and a second raw material layer with different additive concentrations, the additive concentration of the first raw material layer is approximately the same as the additive concentration of the crystals multiplied by the reciprocal of the effective segregation coefficient, and the additive concentration of the second raw material layer is approximately the same as the additive concentration of the crystals, the processing comprising: moving a high-frequency coil for applying the high frequency relative to the first raw material layer toward the second raw material layer to directly heat the raw material by the high frequency, thereby melting the raw material with a weight approximately the same as the weight of the crystals grown from the molten raw material.

Images