JP6464975B2 - Oxygen single crystal growth crucible and oxide single crystal growth method - Google Patents

Description

  The present invention relates to a crucible for growing an oxide single crystal and a method for growing an oxide single crystal. More specifically, after melting a raw material crystal of an oxide single crystal such as sapphire in a crucible, it is possible to facilitate a conditioning operation for seeding. The present invention relates to a crucible for growing an oxide single crystal and a method for growing an oxide single crystal.

  In recent years, white LEDs have been widely used as lighting devices due to demands for energy saving and space saving. This white LED is configured by combining a blue LED in which a GaN-based semiconductor is formed on a sapphire single crystal substrate and a phosphor. For this reason, with the increase in demand for white LEDs, the demand for sapphire single crystal substrates has also increased rapidly. Further, since the cost reduction is required to use the white LED for general illumination, the sapphire single crystal substrate is also required to be reduced in price.

  Generally, a sapphire single crystal substrate is manufactured by cutting out a disk-shaped wafer from a sapphire single crystal ingot grown from a sapphire raw material melt (alumina melt). As a method for growing a sapphire single crystal, a single crystal from a melt represented by the Czochralski method (Czochralski Method) or the EFG method (Edge-defined Film-fed Growth Method, ribbon-like crystal growth method) is used. Unidirectional solidification that solidifies sapphire raw material melt in a crucible represented by the pulling method that pulls up and solidifies, and the vertical Bridgman method (Vertical Bridgman Method) and the VGF method (Vertical Gradient Freeze Method). There are laws.

  Among these, the unidirectional solidification method does not require the grown sapphire single crystal to be pulled up, so that the crystal growth apparatus can be miniaturized and simplified, and the degree of freedom of the growth direction of the single crystal to be grown is high, and the c-axis direction The substrate can be easily obtained, and furthermore, it is possible to produce a large-diameter sapphire single crystal exceeding 6 inches (152.4 mm) in diameter. ing.

  Currently, sapphire single crystal manufacturing technology by unidirectional solidification method is being put into practical use. However, in unidirectional solidification method, after growing, sapphire single crystal is taken out from crucible, and the linear expansion coefficient of crucible material and sapphire Depending on the relationship, since the sapphire single crystal is tightened by the thermal contraction during cooling, there are problems that the crucible is broken when the single crystal is taken out and defects are generated in the sapphire single crystal.

In addition, since the melting point of sapphire is as high as about 2040 ° C., it has been difficult to reduce the running cost because it has been necessary to use an expensive noble metal excellent in high temperature durability as a crucible.
In order to solve these problems, it has been proposed that the material of the crucible is tungsten (W), molybdenum (Mo), or a W—Mo alloy (see Patent Document 1). Since these materials have high-temperature durability and a linear expansion coefficient smaller than that of sapphire, the grown sapphire single crystal can be taken out without destroying the crucible. Moreover, since these materials are cheaper than noble metals, the running cost can be reduced.

  On the other hand, the present applicant has proposed a crucible for growing a sapphire single crystal in which the opening end is not deformed regardless of the height (the length in the growth axis direction) of the obtained sapphire single crystal (Patent Document 2). reference). In this application, a range expressed by a specific formula with respect to the axial length of a sapphire single crystal made of tungsten or a tungsten-molybdenum alloy and having a wall thickness at the opening end obtained by a unidirectional solidification method. In addition, the thickness of the side wall of the opening end is made the thinnest.

  However, in order to grow a sapphire single crystal using a crucible such as tungsten, the temperature gradient in the furnace, heater output and crucible position are maintained in order to perform seeding while maintaining the optimal convex growth interface shape. However, it was very difficult to determine the seeding conditions because it was impossible to make visual adjustments to obtain these findings in the device structure.

  Under such circumstances, there has been a need for a crucible for growing an oxide single crystal that is not only inexpensive and can reduce the running cost but also facilitates the work of setting the seeding conditions.

JP 2011-42560 A JP2015-140291A

  In view of the above-described problems, an object of the present invention is to provide an oxide single crystal growing crucible and an oxide single crystal that can facilitate the process of setting seeding conditions after melting a raw material crystal of an oxide single crystal such as sapphire in a crucible. The object is to provide a crystal growth method.

  The present inventor has intensively studied to solve the above-mentioned problems, and in a crucible for producing a single crystal such as sapphire by a unidirectional solidification method, groove processing at a constant pitch is performed on the outer periphery of the crucible in the area containing the seed crystal. As a result, it was found that a high quality single crystal can be grown at a low cost without excessive melting of the seed crystal by adjusting the heater output, and the present invention has been completed.

That is, according to the first invention of the present invention, an oxide single crystal for containing a seed crystal in a crucible bottom, filling a raw material crystal thereon, and growing the oxide single crystal by a unidirectional solidification method a growing crucible, containing area of the seed crystal, an upper end of the seed crystal is in the 10% to 20% of the position of the crucible depth from the bottom of the crucible, by grooving the crucible outer circumference of the housing area A crucible for growing an oxide single crystal, characterized in that a heat radiation promoting part is formed by the formed groove and fin, and the surface area of the heat radiation promoting part is 1.2 times or more of the case where there is no groove and fin. Provided.

  According to the second invention of the present invention, in the first invention of the present invention, the fin is parallel to the crucible bottom or inclined at an angle of 10 degrees or less with respect to the parallel. A crucible for growing an oxide single crystal is provided.

  According to a third aspect of the present invention, the oxide single crystal according to the first or second aspect of the present invention is characterized in that the groove width is 2 mm or more and the fin width is 3 mm or more. A growing crucible is provided.

  According to a fourth aspect of the present invention, the oxide single crystal growing crucible according to any one of the first to third aspects of the present invention, wherein the groove has a depth of 1 to 5 mm. Is provided.

  According to a fifth aspect of the present invention, the oxide single crystal growth crucible according to any one of the first to fourth aspects of the present invention, wherein the number of fins is 1 to 15. Is provided.

  According to a sixth aspect of the present invention, in the first to fifth aspects of the present invention, the material of the crucible is any one of W, Mo, and a W—Mo alloy. A crucible for crystal growth is provided.

  According to a seventh aspect of the present invention, there is provided a method for growing an oxide single crystal by a unidirectional solidification method, the crucible for growing an oxide single crystal according to any one of the first to sixth aspects of the present invention. The crucible is filled with the seed crystal and the raw material crystal and placed in the heater in the growth furnace, and then heated to melt the entire raw material crystal and at least a part of the seed crystal, and then gradually increase the temperature. By lowering, a method for growing an oxide single crystal is provided, in which a melt is sequentially crystallized on a seed crystal.

  Furthermore, according to the eighth aspect of the present invention, there is provided the method for growing an oxide single crystal according to the seventh aspect of the present invention, wherein the oxide single crystal is sapphire.

  According to the present invention, since the groove for promoting heat dissipation is provided in the outer periphery of the crucible in the area for accommodating the seed crystal, the seeding conditions that have heretofore been difficult when growing single crystals such as sapphire by the unidirectional solidification method The unloading work can be performed easily. Since this crucible can be manufactured at a relatively low cost and can be used repeatedly, the cost for growing a single crystal can be reduced, so that its industrial significance is extremely large.

It is a schematic sectional drawing for demonstrating an example of the apparatus used for the growth method of the oxide single crystal of this invention. It is a schematic sectional drawing of the crucible for oxide single crystal growth of this invention.

  Hereinafter, specific embodiments of a crucible for growing an oxide single crystal and a method for growing an oxide single crystal according to the present invention will be described in detail. The present invention is not limited to the following embodiments as long as it does not depart from the object.

1. The present invention is a crucible for growing an oxide single crystal for containing a seed crystal at the bottom of a crucible, filling a raw material crystal thereon, and growing the oxide single crystal by a unidirectional solidification method. The crystal accommodation area is such that the upper end of the seed crystal is at a position of 10% to 20% of the crucible depth from the crucible bottom, and a heat radiation promoting portion by grooves and fins is provided on the outer periphery of the crucible, The surface area of the heat radiation promoting part is 1.2 times or more of the case where there are no grooves and fins.

  The crucible of the present invention is a cup-shaped crucible 1 as shown in FIG. 2, and the size is not particularly specified. However, from the viewpoint of preventing the size of a general crucible and a growth furnace and the deformation of the crucible, The length is approximately 200 to 300 mm, and the diameter is approximately 100 to 150 mm.

Further, in the present invention, the heat radiation promoting part by the groove 10 and the fin 11 is provided on the outer peripheral part of the crucible in the seed crystal accommodation area, and the groove having the specific depth and width and the fin having the specific width are arranged at a predetermined pitch. Has been. The surface area of the heat dissipation promoting portion needs to be 1.2 times or more that when there are no grooves and fins.
If the surface area of the heat radiation promoting part is less than 1.2 times that of the case where there are no grooves and fins, the heat dissipation is insufficient. On the other hand, if it exceeds 2.5 times, the groove must be deepened, May cause a drop. It is preferable that the surface area of the heat radiation promoting portion is 1.5 to 2 times that in the case where there are no grooves and fins.

  On the other hand, the effect of promoting heat dissipation is obtained even if only fins are attached instead of digging grooves on the outer periphery of the crucible, but since the fin protrudes from the crucible and becomes larger than the outer diameter of the crucible, a step occurs in the crucible. It becomes difficult to handle.

  The fins are preferably parallel to the crucible bottom or inclined at an angle of 10 degrees or less with respect to the parallel. The reason is that the formation of the groove is easy and the strength is stable against the external force.

  The size of the grooves and fins depends on the size of the seed crystal accommodating area, but the groove width is 2 mm or more, the fin width is 3 mm or more, and the groove depth is 1 to 5 mm. Is preferred. If the groove width is 2 mm or more, the fin width is 3 mm or more, and the groove depth is 1 to 5 mm, sufficient heat dissipation can be expected, and the processing is easy and the strength is high. If it is smaller than this range, processing becomes difficult, and a problem is likely to occur in terms of strength. A preferable groove width is 2 to 4 mm, and a fin width is 3 to 5 mm. A more preferable groove depth is 2 to 5 mm. If the depth of the groove is made deeper than 5 mm or the width of the fin is made smaller than 3 mm in order to increase the surface area, the strength of the crucible itself may be lowered, which is not preferable.

  The number of fins is preferably 1 to 15 although it is related to the width and the size of the groove. If the number of fins is 1-15, it has sufficient heat dissipation and mechanical strength. The number of grooves is one more than the number of fins. A more preferable number of fins is 2 to 12.

The thickness of the crucible may be thinner at the opening end than at the bottom as long as deformation of the crucible can be prevented in a plurality of crystal growths. If too much priority is given to preventing deformation of the crucible, the production cost of the crucible increases with an increase in the amount of raw material used, making the crucible heavy and difficult to handle.
Further, in the crucible of the present invention, in order to make it easy to take out the grown single crystal, the inner peripheral surface of the side wall is, for example, 0.8 ° to 3.0 ° from the bottom surface side of the crucible toward the open end side. The diameter may be increased by a taper angle of the order. If the taper angle is less than 0.8 °, the effect is insufficient and defects such as cracks may occur in the single crystal when the grown single crystal is taken out. On the other hand, if the taper angle exceeds 3.0 °, the single crystal after the growth can be easily taken out, but the quality may deteriorate and the product yield may deteriorate.

The crucible of the present invention is not limited by the material, but is preferably W, Mo, or a W—Mo alloy. When sapphire is grown, the coefficient of thermal expansion in the direction perpendicular to the c-axis, which is the growth direction, is about 8 × 10 ⁻⁶ / ° C. at 2050 ° C., so that the coefficient of thermal expansion at 2040 ° C. is a sapphire single crystal. It is necessary to be sufficiently lower than the thermal expansion coefficient.

Therefore, in consideration of cost, workability, etc., tungsten (melting point: 3422 ° C., thermal expansion coefficient at 2050 ° C .: 7.0 × 10 ⁻⁶ / ° C.) is preferable, and molybdenum (melting point: 2620 ° C.) also has a melting point of sapphire. Is higher than the melting point (about 2040 ° C.), and is preferable because it has high temperature durability.

Therefore, since the tungsten-molybdenum alloy also has a sufficiently high melting point and a thermal expansion coefficient sufficiently lower than that of sapphire, it can be used as a material for a crucible for growing a sapphire single crystal of the present invention. In the case of a tungsten-molybdenum alloy, the content of tungsten is preferably 30% by mass or more, more preferably 50% by mass or more, and still more preferably 60% by mass or more.
If the tungsten content is less than 30% by mass, the difference between the thermal expansion coefficients of the tungsten-molybdenum alloy and sapphire cannot be sufficiently increased. As a result, the sapphire single crystal is tightened, and the solidified sapphire single crystal may not be easily taken out from the crucible.

2. TECHNICAL FIELD The present invention relates to a method for growing an oxide single crystal by a unidirectional solidification method, using the crucible for growing an oxide single crystal according to the present invention, and a seed crystal and a raw material crystal in the crucible. And then placed in the heater in the growth furnace, heated to melt the whole raw material crystal and at least part of the seed crystal, and then gradually lower the temperature to melt the melt on the seed crystal. Are sequentially crystallized.

  The oxide single crystal is not limited by its type, but is preferably sapphire.

  FIG. 1 shows a schematic diagram of an apparatus for growing a sapphire single crystal. The apparatus for growing a sapphire single crystal according to this embodiment includes a growth furnace 6 for producing a sapphire single crystal by a known vertical temperature gradient solidification method. The growth furnace 6 is configured such that the crucible 1 and the heater 5 are installed inside the cylindrical chamber 2 and the heat insulating material 3 surrounds the crucible 1 and the heater 5.

  The size of the growth furnace 6 is, for example, about 0.5 to 2 m in diameter and about 1 to 3 m in height, although it depends on the size of the single crystal to be manufactured. Although not shown, two openings are provided in the growth furnace 6, and an inert gas is supplied and discharged. During crystal growth, the chamber 2 is filled with the inert gas. The inert gas is not particularly limited, but argon gas is preferably used. Although not shown, a thermometer for measuring the temperature is installed in the growth furnace 6 below the bottom of the crucible.

  The crucible 1 is formed in a cup shape and is held on a crucible support shaft. In the crucible, seed crystals are stacked at the bottom, and raw material crystals are stacked and stored. The hot zone 4 is formed by the heater 5 installed inside the heat insulating material 3, and the crucible 1 therein is heated. By controlling the amount of electric power supplied to the heater 5, a temperature gradient is generated in the hot zone 4 with a high top and a low bottom. The crucible 1 may be rotated in the hot zone 4 by rotating around the axis by the crucible support shaft 9.

  Using the growth apparatus configured as described above, the seed crystal 8 and the raw material crystal 7 are accommodated in the crucible 1, the crucible 1 is disposed in the growth furnace 6, and heated by the heater 5 to become a raw material for the seed crystal. The adjacent part and the raw material are melted, and then the temperature is gradually lowered, so that the melt is sequentially crystallized on the seed crystal, and the electric power supplied to the heater 5 is adjusted to grow a desired single crystal. .

  Conventionally, for example, if the heater output is adjusted too high, the seed crystal is excessively melted or totally melted, and the crystal grown in that state loses the orientation from the seed crystal, resulting in polycrystals and cracks. It was often easier. Once the crack has occurred, it is very difficult to take out the crystal from the crucible, and the crucible cannot be used. The crucible is expensive and requires about two months of production, and time-consuming work, such as repeated tests in stages so as not to melt the seed crystal, is necessary to determine the seeding conditions.

However, in the present invention, when growing a single crystal by the unidirectional solidification method, as described above, a specific crucible provided with grooves and fins for promoting heat dissipation is used on the outer periphery of the crucible in the area containing the seed crystal. That is, as a crucible for growing an oxide single crystal, a heat dissipation promoting portion by a groove and a fin is provided on the outer periphery of the crucible in the seed crystal accommodation area, and the surface area of the heat dissipation promoting portion is not provided by a groove and a fin. 1.2 times or more.
Therefore, even if the heater output is adjusted too high, it is possible to avoid over-melting or total melting of the seed crystal, and not only can the work of setting the seeding conditions, which was difficult in the past, be performed easily, but Since the crystal grown in (1) maintains the orientation from the seed crystal, it becomes a single crystal and cracks are less likely to occur.

  EXAMPLES The present invention will be described in further detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

  The seed crystal was melted by placing diiodomethane in a transparent container, immersing the obtained crystal in it, and measuring the unmelted height of the seed crystal in a state where refraction unnecessary for observation was removed. evaluated. The appropriate unmelted height is 35 to 45 mm, “◯”, overmelted with an unmelted height of less than 35 mm is “△”, the seed crystal is completely melted with “×”, and conversely the unmelted height Those with a melting shortage of 46 mm or more were determined as “−”.

Example 1
A seed crystal (φ150 × 50 mmH) was placed in the crucible, and 3.5 kg of alumina (sapphire polycrystal) serving as a raw material crystal was filled on the crucible and placed on the support shaft of the growth furnace.
As a crucible, a seed made of tungsten shown in FIG. 2 (outer diameter 180 mm, depth 385 mm, bottom inner diameter 152 mm, opening inner diameter 160 mm, opening thickness 10 mm, diameter increasing from the bottom to the opening with an inclination of 1 °) A crucible outer diameter portion having a width of 50 mm in an area for accommodating crystals and having 13 grooves (fin width: 3 mm, groove width: 2 mm, groove depth: 1 mm) was used.
Thereafter, the chamber was sealed, evacuated to about 0.1 Pa, and argon gas was introduced at a flow rate of 5 L / min. In this state, after heating until the surface temperature of the raw material reached 2040 ° C., the heater output was increased by 0.1 kW, and seeding (leaving for about 6 hours) was performed. Then, it was grown at a speed of 0.2 mm / hr while gradually reducing the heater output, cooled about 12 hr, the crystal was taken out from the crucible, and the melting state of the seed crystal was observed. The results relating to the melting state of the seed crystals are shown in Table 1.
The same experiment was conducted until the surface temperature of the raw material reached 2040 ° C., then the heater output was increased by 0.1 kW and seeding (leaving for about 6 hours) was performed, and the heater output was 1.0 kW. Repeated until increased.

(Examples 2 to 4)
In the same manner as in Example 1, a series of experiments were repeated using a crucible in which only the groove depth was changed to 3, 5, and 7 mm. The results relating to the melting state of the seed crystals are shown in Table 1.

(Comparative Example 1)
The same experiment as in Example 1 was performed using a conventional crucible without groove processing. The results relating to the melting state of the seed crystals are shown in Table 1.

(Examples 5 and 6)
In the case where the material of the crucible was molybdenum and the case was a Mo / W alloy (50/50 wt%), the experiment was performed in the same manner as in Example 1 under the condition that the groove processing level was 5 mm. Table 2 shows the results regarding the melting state of the seed crystals.

"Evaluation"
As shown in Table 1, if a crucible without grooves, which has been used in the past, is used, as in Comparative Example 1, when the heater output from the raw material melting is increased by 0.7 kW, the seed crystals are all melted. There were few things of ○ level.

On the other hand, in Example 1, since a crucible provided with a groove having a depth of 1 mm was used, when the heater output from the raw material melting was increased by 0.7 kW, melting of the seed crystal was suppressed, and Δ was increased and improved. There was an effect. Further, as in Examples 2 to 4, as the groove became deeper, the level of ◯ showed a tendency to increase, and in the groove having a depth of 5 mm, the range of the level ◯ increased by about 1.98 times. Further, in the groove having a depth of 7 mm, the same effect as in the case of the groove having a depth of 5 mm was obtained, but there is a concern that the strength of the crucible may be reduced.
Further, as shown in Table 2, the material of the crucible is not only W, but also in the case of Mo / W alloy (50/50 wt%) of Examples 5 and 6, Mo, and the difference depending on the material is not seen. It can be seen that both can be used as a crucible.

  The crucible of the present invention can be used for the production of blue LED materials, particularly sapphire single crystals, which are widely used as parts of lighting devices. In addition to sapphire single crystals, oxide single crystals grown by a unidirectional solidification method can be used. If it is a crystal, it can also be used for its production.

1 crucible 2 chamber 3 heat insulating material 4 hot zone 5 heater 6 growth furnace 7 raw crystal 8 seed crystal 9 crucible support shaft 10 groove 11 fin

Claims (8)

A crucible for growing an oxide single crystal for containing a seed crystal at the bottom of a crucible, filling a raw material crystal thereon, and growing an oxide single crystal by a unidirectional solidification method,
The seed crystal storage area has an upper end of the seed crystal 10% to 20% of the crucible depth from the crucible bottom, and grooves and fins formed by grooving the crucible outer periphery of the storage area. A crucible for growing an oxide single crystal, characterized in that a heat radiation promoting part is provided and the surface area of the heat radiation promoting part is 1.2 times or more that of a groove and no fin.   The crucible for growing an oxide single crystal according to claim 1, wherein the fins are parallel to the crucible bottom or inclined at an angle of 10 degrees or less with respect to the parallel.   The crucible for growing an oxide single crystal according to claim 1 or 2, wherein a width of the groove is 2 mm or more and a width of the fin is 3 mm or more.   The crucible for growing an oxide single crystal according to any one of claims 1 to 3, wherein the groove has a depth of 1 to 5 mm.   The number of said fins is 1-15, The crucible for oxide single crystal growth in any one of Claims 1-4 characterized by the above-mentioned.   The material for the crucible is any one of W, Mo, and a W-Mo alloy, The oxide single crystal growing crucible according to any one of claims 1 to 5.   A method for growing an oxide single crystal by a unidirectional solidification method, wherein the crucible for growing an oxide single crystal according to any one of claims 1 to 6 is used, a seed crystal and a raw material crystal are filled in the crucible, and a growth furnace After being placed in the heater of the inside, it is heated to melt the entire raw material crystal and at least a part of the seed crystal, and then the temperature is gradually lowered to sequentially crystallize the melt on the seed crystal. A method for growing an oxide single crystal characterized by:   The method for growing an oxide single crystal according to claim 7, wherein the oxide single crystal is sapphire.

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