JP2019182707A - Single crystal growth apparatus - Google Patents

Abstract

To provide a single crystal growth apparatus that can suppress a temperature distribution and a temperature gradient inside the single crystal growth apparatus from varying owing to industrial repetition of growth of a single crystal as much as possible, and is low-cost and high in yield.SOLUTION: A single crystal growth apparatus that is used for a crystal growth method of growing a single crystal while lifting a seed crystal brought into contact with a surface of a raw material melt, and arranged where a crucible is covered from above, and lifts the seed crystal, and that has plate-like refractory materials 4, having holes 4H for passing a lift shaft, divided across a straight line crossing the hole for passing the lift shaft is characterized in that: one refractory material has a front end of its mating surface part positioned below a mating surface part of the other refractory material; the mating surface parts of the refractory materials have mutually opposed planes one over the other; and the planes adhere to each other in single crystal growth.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a single crystal growing apparatus used for a crystal growing method for growing a single crystal while pulling up a seed crystal brought into contact with the surface of a raw material melt.

  As a method for growing a single crystal, the Czochralski method, in which a seed crystal is brought into contact with the surface of the raw material melt after the melting of the crucible filled with the raw material and the seed crystal is pulled up, is widely used. Yes.

  In growing single crystals, temperature distribution and temperature gradient in the furnace are important. In the growth process of the single crystal, the single crystal is grown while making a slight cooling state from the thermal equilibrium state and releasing the latent heat generated when the raw material melt (liquid) is changed to the crystal (solid). Therefore, it is important to control the temperature distribution and temperature gradient in the furnace during single crystal growth in order to produce industrially usable single crystals.

For example, when the furnace temperature distribution has a narrow interval between the respective isotherms, and the furnace temperature gradient is steep, temperature control is easy and latent heat associated with crystallization can be sufficiently released. Therefore, it becomes easy to control the shape of the single crystal.
However, the temperature difference inside the single crystal to be grown becomes large, and crystal defects are introduced due to thermal strain caused by thermal expansion of the crystal, so that polycrystallization tends to occur. Further, there is a problem that crystal quality is deteriorated due to crystal cracking due to thermal strain or crystal defects introduced inside the crystal without being polycrystallized.

On the other hand, when the temperature distribution in the furnace is wide and the temperature gradient in the furnace is gentle, the temperature difference inside the single crystal to be grown becomes small, resulting from the thermal expansion of the crystal. Thermal strain is reduced, and polycrystallization and cracking due to thermal strain are less likely to occur.
However, since crystal growth is performed along the isothermal distribution of the raw material melt, single crystal growth control is extremely possible when the temperature gradient in the furnace is gentle and the interval between each isotherm is wide. It becomes difficult.
For example, the output control width of the heating means in the furnace during single crystal growth, such as a resistance heating heating element and an induction heating coil, becomes narrow. In addition, crystal growth becomes sensitive to temperature changes accompanying changes in the environment around the single crystal growth apparatus and in-apparatus components. Even if a slight temperature fluctuation inside the single crystal growth apparatus occurs, a phenomenon in which rapid crystal growth occurs or a phenomenon in which crystal growth does not occur occurs. In such unstable crystal growth, there are problems of polycrystallization due to crystal defects introduced into the crystal and cracking due to the generation of stress concentration portions due to abrupt crystal shape change. Further, since the desired single crystal shape cannot be obtained, when the single crystal is processed into a wafer, a portion where the wafer cannot be obtained occurs, and the yield during wafer processing decreases.

Thus, in the growth of a single crystal, it is necessary to optimize the temperature distribution and temperature gradient inside the single crystal growth apparatus.
By the way, the present inventor relates to a heat insulating structure disposed around a heating element in a single crystal growing apparatus, and suppresses the radiant heat from the heating element from leaking outside through the heat insulating material. As a technique that can suppress non-uniform temperature distribution in the inner region and a decrease in thermal efficiency, a heat insulating structure described in the following Patent Document 1 was derived.

Japanese Patent Laid-Open No. 2016-200254

As shown in FIG. 5 (a), the technique described in Patent Document 1 is a heat insulating structure 53 arranged around a heating element (heaters 54 and 55, a crucible 51, a raw material melt 52), and has a height. A plurality of heat insulating materials 53 _{1 to} 53 ₅ stacked in the direction, and as shown in FIG. 5B, in one heat insulating material 53 _n adjacent to the height direction and the other heat insulating material 53 _{n + 1} , one to the other of the heat insulating material _{53 n + 1} and the surface facing the heat insulator 53 _n protrusion 53a _n are formed, the other heat insulating material _{53 n +} one in ₁ heat insulator 53 _n opposed to the surface protrusion 53a recesses 53b n + ₁ is in the formed configuration corresponding to _n. In FIG. 5A, 56 is a chamber, 57 is a seed crystal, 58a is a seed crystal holding portion, 58 is a pulling shaft, and 59 is a crucible support.
According to the technique described in Patent Document 1, the heat insulating materials stacked adjacent to each other in the height direction have concave portions and convex portions, so that the radiant heat from the heating element passes between the heat insulating materials by the side walls of the convex portions. Can be prevented from leaking outside.
For this reason, the present inventors configure a single crystal growth apparatus using a technique of a heat insulating structure in which heat insulating materials stacked adjacent to each other in the height direction described in Patent Document 1 have a concave portion and a convex portion. Then, it was thought that the temperature distribution and temperature gradient inside the single crystal growing apparatus could be optimized.

  However, as a result of repeating further trial and error, the present inventors, as a result of repeating trial and error, described the technology of the heat insulating structure described in Patent Document 1 in which the heat insulating materials stacked adjacent to each other in the height direction have concave portions and convex portions. The single crystal growth equipment used is designed to maintain the optimization of the temperature distribution and temperature gradient inside the single crystal growth equipment while reducing costs in the case where industrial single crystal growth is repeated. It has been found that there is a problem to be further improved in order to improve the performance.

  In view of the above circumstances, the present invention can suppress changes in temperature distribution and temperature gradient inside a single crystal growth apparatus as much as possible by repeating industrial growth of a single crystal as much as possible. An object is to provide a crystal growth apparatus.

  In order to achieve the above object, a single crystal growing apparatus according to the present invention is used in a crystal growing method for growing a single crystal while pulling up a seed crystal brought into contact with the surface of a raw material melt, and is disposed at a position covering the upper part of the crucible. In the single crystal manufacturing apparatus, the plate-like refractory having a hole for passing the pulling shaft and pulling the seed crystal is divided with a straight line crossing the hole for passing the pulling shaft as a boundary. The joint portions of the refractories are positioned at the lower ends of the joint portions of the other refractories, and the joint portions of the refractories of each other. In FIG. 2, the upper and lower sides have opposite planes, and the planes are closely adhered to each other during single crystal growth.

  Further, in the single crystal growth apparatus of the present invention, each joint portion of the refractory has a concave portion and a convex portion, and the concave portion of one of the refractories and the convex portion of the other refractory, The refractory convex portion and the concave portion of the other refractory are abutted, and the concave portion and the convex portion of each of the refractories are each approximately half the thickness of the refractory. It is preferable to have a height of

  Further, in the single crystal growth apparatus of the present invention, the joint portion of each refractory is formed of an inclined surface, and is formed in a structure in which the inclined surfaces of the refractories are mutually abutted. The inclined surface preferably has an inclination angle of 40 ° or more and less than 70 °.

  Moreover, in the single crystal growth apparatus of this invention, it is preferable that the joint part front-end | tip of the said refractory has a corner | angular part formed in C surface or R surface.

  According to the present invention, a single crystal growth apparatus that can suppress changes in temperature distribution and temperature gradient inside the single crystal growth apparatus as much as possible by repeatedly growing a single crystal industrially, and has a low cost and high single crystal yield. Can be provided.

It is explanatory drawing which shows roughly an example of the single crystal growth apparatus which can be applied to embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the principal part structure of the single crystal growth apparatus concerning 1st Embodiment of this invention, (a) is the straight line which crosses the hole for passing a raising axis | shaft arrange | positioned in the position which covers the crucible upper part. The perspective view which shows the whole structure of the plate-shaped refractory material divided | segmented as a boundary, (b) is the perspective view which shows the joint part of one plate-shaped refractory material divided | segmented into (a), (c) (B) is a diagram showing the relationship between the height and length of the convex portion at the joint of the plate-like refractory shown in (b) and the thickness of the plate-like refractory, (d) is a plate-like refractory shown in (c) The figure which shows the modification of the corner | angular part of the joint part in a refractory, (e) is a figure which shows the other modification of the corner | angular part of the joint part in the plate-like refractory shown in (c). It is explanatory drawing which shows the principal part structure of the single crystal growth apparatus concerning the modification of embodiment of FIG. 2, (a) is the straight line which crosses the hole for passing the raising axis | shaft arrange | positioned in the position which covers the crucible upper part. FIG. 2 is a perspective view showing the entire configuration of a plate-like refractory divided with reference to the boundary, and (b) is a side view of (a). It is explanatory drawing which shows the principal part structure of the single crystal growth apparatus concerning 2nd Embodiment of this invention, (a) is the straight line which crosses the hole for passing the raising axis | shaft arrange | positioned in the position which covers the crucible upper part. The perspective view which shows the whole structure of the plate-shaped refractory material divided | segmented as a boundary, (b) is the perspective view which shows the joint part of one plate-shaped refractory material divided | segmented into (a), (c) Is a diagram showing the inclination angle of the inclined surface in the joint portion of the plate-like refractory shown in (b), (d) is a modification of the corner portion of the joint portion in the plate-like refractory shown in (c) (E) is a figure which shows the other modification of the corner | angular part of the joint part in the plate-like refractory shown in (c). BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows schematically the heat insulation structure of patent document 1, (a) is a figure which shows the structural example of the single-crystal growth apparatus provided with the heat insulation structure, (b) is the heat insulation structure of (a). It is a figure which shows the structure of the heat insulating material contained in. In the conventional single crystal growth apparatus, an explanatory diagram showing the configuration of a plate-like refractory material that is divided at a position that covers the crucible upper portion and that is divided with a straight line that passes through a hole for passing a pulling shaft as a boundary. a) is a perspective view showing the overall configuration, (b) is a perspective view showing a joint portion of one plate-like refractory divided as shown in (a), and (c) is a side view of (b). .

Hereinafter, an embodiment for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view schematically showing an example of a single crystal growing apparatus used in the most general Czochralski method as a single crystal manufacturing method, which can be applied to an embodiment of the present invention.
In the Czochralski method, a single crystal called a seed crystal cut according to a certain crystal orientation is attached to the tip of a pulling shaft that can move up and down, and the tip of the single crystal is brought into contact with the surface of the raw material melt via the pulling shaft. This is a method for producing a single crystal by increasing the diameter while propagating the properties of the seed crystal by gradually pulling it up while rotating.

  As shown in FIG. 1, a single crystal growing apparatus that can be applied to the present embodiment includes a crucible 1, a refractory 3 disposed around the crucible 1, and a refractory disposed at a position covering the crucible 1. The refractory that constitutes the support 4 that supports the crucible 1, the lifting shaft 8 provided with a rotating mechanism (not shown), the heating means 5 that heats the crucible 1 (high-frequency induction coil in the example of FIG. 1), and the crucible 1. 9 is provided. The high frequency induction coil constituting the heating means 5 is provided with a power source (not shown) for supplying high frequency power. The heating means 5 may be composed of a resistance heating element.

  In the production of the single crystal, the crucible 1 filled with the single crystal raw material is heated by the heating means 5 to obtain the raw material melt 2. Thereafter, the seed crystal 7 attached to the tip of the pulling shaft 8 is rotated and brought into contact with the surface of the raw material melt 2, and the pulling shaft 8 is maintained while keeping the seed crystal in contact with the surface of the raw material melt 2. A single crystal is manufactured while gradually pulling up.

  However, regarding the refractory 3 disposed around the crucible 1 in the single crystal growing apparatus having the above-described configuration, the heat insulating materials stacked adjacent to each other in the height direction described in Patent Document 1 derived by the present inventor. If the refractories stacked in a plurality in the height direction and stacked adjacent to each other in the height direction using the technology of the heat insulating structure having a recess and a projection, have a recess and a projection, It can suppress that the radiant heat from the raw material melt 2 and the crucible 1 leaks outside.

  Here, the present inventors believe that if the radiation heat from the raw material melt 2 and the crucible 1 can be prevented from leaking to the outside, the temperature distribution and temperature gradient inside the single crystal growth apparatus can be maintained in an optimized state. And the refractory 3 arrange | positioned around the crucible 1 is laminated | stacked in multiple numbers in the height direction, and the refractory 3 laminated | stacked adjacent to a height direction has a recessed part and a convex part. Using a single crystal growth apparatus, an experiment was repeated to grow a single crystal industrially.

  However, when the growth of the single crystal is repeated, the heat-insulating materials described in Patent Document 1 are stacked adjacent to each other in the height direction on the refractory 3 disposed around the crucible 1 so that the concave portions and the convex portions are formed. It has been found that there is a problem that the yield of the single crystal is lowered due to the gradual shift of the temperature distribution and temperature gradient inside the single crystal growth apparatus using the technology of the heat insulating structure possessed.

  The deviation of the temperature distribution and temperature gradient inside the single crystal growth apparatus is considered to be due to the change over time in the furnace components generated by the thermal cycle in the single crystal growth process. In the single crystal growth process, the temperature inside the single crystal growth apparatus is increased for raw material melting and crystal growth from a state in which a raw material is placed in a crucible in a furnace at room temperature and a refractory is disposed. The temperature raised at this time needs to be sufficient to melt the raw material. In addition, after the crystal growth is completed, it is necessary to cool to room temperature again in order to take out the grown single crystal.

  In the case of melt growth, the temperature until the raw material installed in the single crystal growing apparatus is melted is the melting point of the raw material (single crystal). For example, silicon, which is a typical semiconductor material, has a melting point of about 1414 ° C. In the oxide single crystal, lithium tantalate has a melting point of about 1650 ° C. and sapphire has a melting point of about 2050 ° C. The components inside the single crystal growth apparatus change over time by such a thermal cycle in which the temperature rises from room temperature to a melting point exceeding 1000 ° C. and then the temperature is lowered again to room temperature. A refractory can be considered as a main component that changes with time.

  The material of the refractory is selected depending on the operating temperature and atmosphere. The refractory also repeats the thermal cycle as described above, thereby causing a reaction with the atmosphere inside the single crystal growth apparatus and a slight deterioration due to sublimation. In addition, the refractory repeats expansion and contraction. However, in order to shield heat, a refractory usually has a low thermal conductivity. For this reason, in the process through the thermal cycle in the growth of the single crystal, a temperature difference is generated inside the refractory. As a result, by repeating the thermal cycle as described above, thermal strain is generated due to the temperature distribution and temperature gradient inside the refractory, and the refractory is deformed.

  Here, the heat insulation structure (refractory material) arranged around the crucible described in Patent Document 1 has a configuration in which, for example, a plurality of brick-like heat insulation materials (refractory materials) are stacked in the height direction, Thickness is large compared with the heat insulation structure (refractory material) to arrange | position. If the heat insulating material (refractory) laminated adjacent to each other in the height direction with a large thickness has a concave portion and a convex portion, the radiant heat from the heating element is generated between the heat insulating materials (refractory) by the side walls of the convex portion. It is thought that it is easy to suppress leakage through the exterior.

By the way, the refractory disposed in the upper part of the crucible has a hole 4H for pulling up the seed crystal and passing the pulling shaft as shown in FIG. 6 (a) in order to take out the grown single crystal. In many cases, it is formed in a plate shape that is divided into two substantially semicircular shapes in a vertical direction (direction cut by a vertical surface) with a straight line crossing the hole 4H passing therethrough as a boundary.
The reason is that if the refractory placed at the top of the crucible is formed into a plate that is divided with a straight line across the hole for passing the lifting shaft as a boundary, remove one plate-like refractory. The single crystal grown to a diameter larger than the diameter of the hole for passing the pulling shaft can be taken out, whereas in the case where the refractory disposed at the upper part of the crucible is not divided, the pulling shaft is passed. This is because it becomes impossible to take out a single crystal grown to a diameter larger than the diameter of the hole.

  However, at the time of deriving the technique described in Patent Document 1, the present inventor has radiated heat from the heating element in the heat insulating structure (refractory) having a large thickness disposed around the crucible through the heat insulating material. Although the refractory disposed at the top of the crucible is divided into two substantially semicircular shapes in a vertical direction with a straight line crossing the hole for passing the lifting shaft as a boundary. However, the problem of deformation caused by the formation of a single crystal and the problem of deformation caused by repeated thermal cycles in the process of growing an industrial single crystal have not been noticed.

  In the conventional single crystal growth apparatus used for the crystal growth method for growing the single crystal while pulling up the seed crystal brought into contact with the surface of the raw material melt, the crucible including the single crystal growth apparatus described in Patent Document 1 is also included. As shown in FIG. 6 (b), the refractory disposed in the upper part is divided into a substantially semicircular shape in the vertical direction with a straight line crossing the hole 4H through which the lifting shaft is passed as a boundary. It had a structure in which the vertical surfaces of the refractory were butted together.

  If deformation occurs in the refractory disposed in the upper part of the crucible having such a structure (particularly in the vicinity of the hole 4H through which the lifting shaft is passed), a gap is likely to be generated at the joint portion between the refractories. If atmospheric gas leaks from this gap, heat outflow due to convective heat transfer occurs. In addition, when light leaks, heat outflow due to radiation occurs. Such a heat outflow is locally generated from a gap generated by deformation of the refractory. As a result, the temperature distribution and temperature gradient inside the single crystal growth apparatus are locally changed, the symmetry of the temperature distribution and temperature gradient inside the single crystal growth apparatus is broken, and the yield of the single crystal is lowered.

The refractory placed in the upper part of the crucible has a large amount of heat transported by convection heat transfer from the vicinity of the hole for passing the pulling shaft when the single crystal is grown, and is heated from the side of the hole. Therefore, the temperature distribution in the vicinity of the hole is the highest, the temperature is lower toward the periphery, and the temperature distribution and temperature gradient are symmetrical with respect to a concentric isotherm centering on the vicinity of the hole for passing the pulling shaft. have.
However, as described above, when the inventors repeated a thermal cycle in the process of growing an industrial single crystal, the refractory disposed on the upper part of the crucible is particularly near the hole for passing the lifting shaft. However, it has been found that it is easy to deform due to thermal strain caused by temperature distribution and temperature gradient in the refractory. When a gap is generated in the joint portion originally designed due to deformation of the refractory disposed at the upper part of the crucible, convective heat transfer by atmospheric gas and heat outflow by radiation are generated from the gap.
The deformation of the refractory disposed in the upper part of the crucible is, for example, as shown in FIGS. 6 (a) and 6 (b), when the substantially disk-shaped refractory 4 crosses the hole 4H for passing the lifting shaft. for straight line was divided into two and refractory 4 ₁ and refractory 4 ₂ in the vertical direction as a boundary configured to, hole 4H for passing the pulling shaft in the center of the circular is the outer shape of the refractory 4 Since the nearby seam is located in the center of the upper part of the crucible, the temperature tends to be high, and the deformation becomes large. The deformation of this part generally has a tendency that the vicinity of the hole 4H for passing the lifting shaft positioned at the center of the circle is warped upward due to heat from below, so that the lifting shaft positioned at the center of the circle is A gap is generated in the vicinity of the hole 4H for passing through.

  When deformation occurs in the refractory disposed on the upper part of the crucible, the yield of the single crystal is lowered, and thus it is necessary to replace the refractory disposed on the deformed upper part of the crucible. However, if the number of times of repeating the thermal cycle in the process of growing an industrial single crystal until the deformation of the refractory disposed at the upper part of the crucible occurs, the replacement cost of the refractory increases.

However, when the present inventor has derived the technique described in Patent Document 1, as described above, the refractory disposed on the upper portion of the crucible is perpendicular to the straight line passing through the hole for passing the lifting shaft. The problem of deformation caused by being formed into a plate that is divided into two substantially semicircular shapes, and the problem of deformation caused by repeated thermal cycles in the process of growing industrial single crystals, have come to focus attention. It wasn't.
As a result of repeating further trial and error, the present inventors used the technique of a heat insulating structure described in Patent Document 1 in which heat insulating materials stacked adjacent to each other in the height direction have concave and convex portions. Single crystal growth equipment improves the yield of single crystals by maintaining the optimization of the temperature distribution and temperature gradient inside the single crystal growth equipment while reducing costs when industrially repeating single crystal growth. In order to make this happen, it was found that there were problems to be further improved.

  Therefore, the present inventors have found that the deformation of the refractory disposed at the upper part of the crucible tends to warp upward in the vicinity of the hole for passing the lifting shaft positioned at the center of the circle. As a means to prevent a gap from occurring even if the vicinity of the hole for passing through is warped upward, the joint portion of each refractory is divided with a straight line crossing the hole for passing the lifting shaft as a boundary The tip of the joint portion of one refractory is located below the joint portion of the other refractory, and has a plane that faces the upper and lower sides of the joint portion of the refractory. The inventors have come up with a configuration of the single crystal growth apparatus of the present invention in which the flat surfaces are in close contact with each other during single crystal growth.

First Embodiment FIG. 2 is an explanatory view showing the configuration of the main part of a single crystal growth apparatus according to the first embodiment of the present invention. (A) is for passing a pulling shaft disposed at a position covering the upper part of the crucible. The perspective view which shows the whole structure of the plate-like refractory divided by making the straight line which crosses the hole of a boundary into a boundary, (b) is the joint part of one plate-like refractory divided as shown in (a). The perspective view shown, (c) is a diagram showing the relationship between the height and length of the convex portion at the joint portion of the plate-like refractory shown in (b) and the thickness of the plate-like refractory, (d) is ( The figure which shows one modification of the corner | angular part of the joint part in the plate-like refractory shown in c), (e) is another modification of the corner part of the joint part in the plate-like refractory shown in (c) FIG. FIG. 3 is an explanatory view showing the configuration of the main part of a single crystal growth apparatus according to a modification of the embodiment of FIG. 2, and (a) shows a hole for passing a pulling shaft disposed at a position covering the upper part of the crucible. The perspective view which shows the whole structure of the plate-shaped refractory material divided | segmented on the basis of the crossing straight line, (b) is a side view of (a). In addition, in the figure used for embodiment of this invention, it corresponds to the technique of the heat insulation structure in which the heat insulating materials laminated | stacked adjacent to the height direction of patent document 1 have a recessed part and a convex part for convenience. The configuration of the portion where the refractory 3 and the refractory 4 are stacked in the height direction is omitted.

In the single crystal growth apparatus of this embodiment, as shown in FIGS. 2 (a) and 2 (b), the joint portion of each refractory 4 ₁ (4 ₂ ) is the recess 4b ₁ (4b ₂ ). protrusions _4a 1 has a (4a _2), one of the refractory _{4 1} recess 4b ₁ and the other refractory _{4 2} of the convex portion 4a _2, one of the refractory _{4 of the} projecting portion 4a ₁ and the other refractory It is formed on the spigot structure to match the recess 4b ₂ of the object 4 _2.
Recess _4b 1 of the refractory respective ₄ 1 _{(4 2)} (4b ₂₎ and the protrusions _4a 1 (4a _2), respectively, as shown in FIG. 2 (c), refractory ₄ 1 _{(4 2)} It has a height (hb≈1 / 2tx, ha≈1 / 2tx) that is approximately ½ times the thickness (tx), and is 0.4 to 0.6 times the thickness of the refractory 4 ₁ (4 ₂ ). (Lb = (0.6 to 0.4) tx, La = (0.4 to 0.6) tx).
And each refractory 4 ₁ (4 ₂ ) has a plane which faces the upper part and the lower side in the concave part 4b ₁ (4b ₂ ) and the convex part 4a ₁ (4a ₂ ). The opposing flat surfaces are arranged so as to be in close contact during single crystal growth.

According to single crystal growing apparatus of the present embodiment, the refractory of the respective 4 _{1 (4 2)} the seam portion of, one of the refractory 4 ₁ recess 4b ₁ and the other refractory 4 ₂ of the convex portion 4a ₂ , formed in one of the refractory _{4 1} spigot structure matched with the recess 4b ₂ of the convex portion 4a ₁ and the other refractory _{4 2,} in the recess _4b 1 (4b ₂₎ and the protrusions _4a 1 (4a ₂₎ Since the planes facing the upper side and the lower side are brought into close contact with each other during single crystal growth, the concave portion 4b ₁ (4b ₂ ) and the convex portion 4a ₁ (4a ₂ ) of the refractory are brought into contact with each other, whereby the refractory Even if the deformation in which the vicinity of the hole 4H for passing the pulling shaft located at the center of the warp is warped upward occurs, the vertical portion of the convex portion 4a ₁ of the _one refractory 41 located at the lower end of the joint portion direction of the plane, over the length of the convex portion 4a _1, the joint Tip for overlaps in a state of close contact with the vertical plane of the recess 4b ₂ of the other refractory 4 ₂ positioned on the upper side, cut off the gas convection, light can be prevented leakage (radiation).

In addition, the concave portion 4b ₁ (4b ₂ ) and the convex portion 4a ₁ (4a ₂ ) forming the inlay structure of the joint portion of each refractory 4 ₁ (4 ₂ ) in the single crystal growth apparatus of the present embodiment are It is important to have a flat surface facing the lower side and to arrange the flat surfaces facing the upper side and the lower side so as to be in close contact during single crystal growth. If there is a gap in this flat portion, gas convection is blocked and light (radiation) leakage cannot be prevented.
On the contrary, it is preferable that a gap is provided between the joints in the vertical direction at the tips of the protrusions 4a ₁ (4a ₂ ) (the bases of the recesses 4b ₁ (4b ₂ )) at room temperature. The gap between the joint portions in the vertical direction can be designed according to the temperature at which the crystal is grown in the apparatus. If there is no gap between the vertical seams at room temperature, the vertical seams (especially between the seams near the crucible) when the refractory thermally expands due to the temperature rise during heating. ) Is overstressed, there is a risk of the refractory being displaced or damaged. Therefore, considering the amount of thermal strain at the working temperature of the refractory, it is preferable to have a structure with a gap between the vertical joints at room temperature as shown in FIGS. 3 (a) and 3 (b). .
In the example of FIGS. 3 (a) and 3 (b), the planes facing the upper side and the lower side of the concave portion 4b ₁ (4b ₂ ) and the convex portion 4a ₁ (4a ₂ ) have a gap at room temperature. And it becomes the structure closely_contact | adhered when heated.

Further, according to the single crystal growing apparatus of the present embodiment, the recess _4b 1 of the refractory respective ₄ 1 _{(4 2)} (4b ₂₎ and convex portions _4a 1 a (4a _2), respectively, refractory ₄ 1 ( 4 ₂ ) having a height (hb≈1 / 2tx, ha≈1 / 2tx) that is approximately ½ times the thickness (tx) of the _two refractories, and in close contact with the upper and lower sides of each refractory Since the thickness of each of the refractories is made substantially uniform, it is possible to prevent severe deformation only at the joint portion of one refractory, cracking or breakage of the convex portion, or generation of a gap. This effect is known as a result of trial and error regarding the respective heights of the concave portions 4b ₁ (4b ₂ ) and the convex portions 4a ₁ (4a ₂ ) of the refractories 4a ₁ (4a ₂ ). It came to get.

When the concave portion and the convex portion of each refractory are not configured to have a height that is approximately ½ of the thickness of the refractory, respectively, one refractory in which the tip of the joint portion is located on the lower side, The thickness of the part which overlaps by the upper side and the lower side differs with the other refractory material in which the front-end | tip of a joint part is located above.
However, when the thickness of the overlapping part is different between the upper side and the lower side, only the joint part of one refractory is deformed severely, causing cracks and breakage of the convex part, or generation of gaps in the flat part of the concave part and convex part. Is likely to occur.

Further, according to the single crystal growing apparatus of the present embodiment, the recess _4b 1 of the refractory respective ₄ 1 _{(4 2)} (4b ₂₎ and the protrusions _4a 1 (4a ₂₎ a refractory ₄ 1 ₍₄ 2) A structure having a length (Lb = (0.6 to 0.4) tx, La = (0.4 to 0.6) tx) that is 0.4 to 0.6 times the thickness (tx) of Therefore, even if deformation occurs in the refractory, it becomes easy to prevent the generation of gaps between the flat portions of the concave portion and the convex portion, and the cracking and breakage of the convex portion.
When the length of the concave portion and the convex portion of each refractory is less than 0.4 times the thickness of the refractory, gaps are likely to be generated in the flat portions of the concave and convex portions when the refractory is deformed. The temperature difference in the refractory is proportional to the thickness of the refractory, and as the refractory becomes thicker, the temperature difference in the refractory widens and the thermal stress increases and the amount of deformation of the refractory increases. For this reason, the length of the concave portion and the convex portion of each refractory is required to be 0.4 times or more the thickness of the refractory, and is preferably longer as the thickness of the refractory increases.
However, if the length of the concave and convex portions of each refractory exceeds 0.6 times the thickness of the refractory, when the refractory is deformed, one refractory with the tip of the joint located below One of the refractory parts where the tip of the joint part is located on the lower side is excessively restrained when the convex part of the joint is in contact with the concave part of the other refractory with the tip part of the joint part located on the upper side. There is a risk that the convex portion of the object will break.
Therefore, in the single crystal growth apparatus of the present embodiment, preferably, the lengths Lb and La of the concave portions 4b ₁ (4b ₂ ) and the convex portions 4a ₁ (4a ₂ ) of the respective refractories 4 ₁ (4 ₂ ) are The length of the refractory is preferably 0.5 times the length (Lb = 0.5 tx, La = 0.5 tx).

It should be noted that the tips of the convex portions constituting the seam portion are easily chipped. In particular, in the convex portion of one refractory where the tip of the joint portion is located on the lower side, the corner portion on the side close to the root of the concave portion of the other refractory where the tip of the joint portion is located on the upper side is refractory The stress is concentrated during the deformation of the steel, and chipping is likely to occur.
For this reason, in the single crystal growth apparatus of this embodiment, Preferably, the corner | angular part of the joint part front-end | tip of a refractory (especially convex part of _one refractory 41 in which the front-end | tip of a joint part is located below) in 4a _1, the corners closer to the root of the other refractory 4 _second recess 4b ₂ the front end of the seam section is positioned on the upper side side), as shown in FIG. 2 (d), FIG. 2 (e) It is desirable to have a configuration formed on the C and R planes.

Second Embodiment FIG. 4 is an explanatory view showing the configuration of the main part of a single crystal growth apparatus according to a second embodiment of the present invention. FIG. 4 (a) is for passing a pulling shaft arranged at a position covering the upper part of the crucible. The perspective view which shows the whole structure of the plate-like refractory divided by making the straight line which crosses the hole of a boundary into a boundary, (b) is the joint part of one plate-like refractory divided as shown in (a). (C) is a diagram showing the inclination angle of the inclined surface in the joint portion of the plate-like refractory shown in (b), (d) is a joint portion in the plate-like refractory shown in (c) The figure which shows the one modification of this corner | angular part, (e) is a figure which shows the other modification of the corner | angular part of the joint part in the plate-like refractory shown in (c).
In the single crystal growth apparatus of the present embodiment, as shown in FIG. 4A, the joint portion of each refractory 4 ₁ (4 ₂ ) is formed of an inclined surface, and each refractory 4 ₁ (4 _2). ) In such a structure that the inclined surfaces abut each other.
The inclined surface 4 ₁ (4 ₂ ) of the refractory has an inclination angle (30 ° ≦ αx <70 °) of 40 ° or more and less than 70 ° with respect to the horizontal plane as shown in FIG. 4 (c).

The joint portion of each refractory 4 ₁ (4 ₂ ) in the single crystal growth apparatus of this embodiment is an optimum structure when the thickness of the refractory is small and the inlay structure as in the first embodiment is difficult. .
When viewed from the side, the joint portion has a structure in which a right triangle is inverted and butted and the hypotenuses are brought into contact with each other. Therefore, even if the refractory is deformed, the inclined surfaces of the refractory 4 ₁ (4 ₂ ) are in close contact with each other as long as it corresponds to the length Lc of the base of the right triangle shown in FIG. In this state, gas convection can be cut off and light (radiation) leakage can be prevented.

And according to the single-crystal growth apparatus of this embodiment, the inclination angle of the inclined surface which comprises the joint part of each refractory 4 ₁ (4 ₂ ) is 40 degrees or more and less than 70 degrees (30 degrees) with respect to a horizontal surface. Having a ≦ αx <70 °), even if variations in refractory, occurrence of a gap of the inclined faces, the seam portion tip seam portion at one refractory 4 ₁ located on the lower side It becomes easy to prevent breakage of the tip.

When the inclination angle of the inclined surface of the refractory exceeds 70 °, there is a high possibility that a gap is generated at the joint when the refractory is deformed.
On the other hand, when the inclination angle of the inclined surface of the refractory is less than 40 °, during deformation of the refractory, the inclined surface at one refractory 4 ₁ the front end of the seam section is positioned on the lower side, the seam portion tip stress too constrained state in contact with the inclined surface of the other refractory 4 ₂ positioned on the upper side is large occurs, the joint at the seam portion one refractory tip is positioned below the 4 ₁ There is a possibility that the lower end of the part may break.
Therefore, the single crystal growing apparatus of the present embodiment, preferably, when the inclination angle of the inclined surface of the refractory and 45 °, the inclined surface at one refractory 4 ₁ the front end of the seam section is positioned on the lower side If, balanced the stress on the inclined surface of the seam portion one refractory tip is positioned above the 4 _2, occurrence of a gap of the inclined faces, seam section located below the tip of the It becomes easy to prevent the tip of the joint part in _one refractory 41 to break.

In addition, the tip of the joint portion formed by the inclined surface is sharp and easily lost. In particular, the corners of the front end of the seam section in one of the refractory 4 ₁ the front end of the seam section is positioned on the lower side, prone to chipping stress is concentrated upon deformation of the refractory.
Therefore, in the single crystal growing apparatus of the present embodiment, preferably, the corners of the tip end of the joint portion of the refractory (especially, combined in one of the refractory 4 ₁ the front end of the seam section is positioned on the lower side As shown in FIGS. 4 (d) and 4 (e), it is desirable that the corners at the tips of the eyes be formed on the C and R surfaces. Moreover, when the corner | angular part of the front-end | tip part of each refractory is formed in C surface or R surface, it has a clearance gap near the front-end | tip of the joint part in each refractory 4 ₁ (4 ₂ ). As with the gap between the vertical joints at the tips of the protrusions (the bases of the recesses) in the spigot structure that forms the joints of the single crystal growth apparatus of the first embodiment, the temperature rises during heating. To prevent misalignment or breakage of the refractory due to excessive stress applied to the joints having an inclination angle (particularly, the joints close to the crucible) when the refractory is thermally expanded. it can.

  Examples of the present invention will be specifically described below with reference to comparative examples. Here, a lithium tantalate single crystal growth method will be described as an example. The present invention is not limited to the following examples.

Example 1
The single crystal growth apparatus of Example 1 was provided with a configuration corresponding to the single crystal growth apparatus of the first embodiment shown in FIGS.
The procedure for growing the lithium tantalate single crystal was performed as follows. At room temperature, an iridium crucible 1 is filled with a raw material 2 of lithium tantalate, and the crucible 1 is heated by a high frequency induction coil 5 made of copper. A single crystal is grown from the seed crystal 7 by melting the lithium tantalate raw material in the crucible 1 and pulling it vertically at a speed of 1-5 mm / h while rotating the iridium pulling shaft 8 at 1-20 rpm. . After the growth of the single crystal is completed, the temperature is gradually lowered to room temperature, and then the single crystal grown is taken out.
In Example 1, such single crystal growth was continuously repeated.

In the single crystal growth apparatus of Example 1, the refractory disposed at a position covering the upper part of the crucible was made of alumina. The disc-shaped refractory was divided into two, and two semicircular refractories were used in combination. As shown in FIG. 2, the joint portion has an inlay structure in which the concave portion 4b ₁ (4b ₂ ) and the convex portion 4a ₁ (4a ₂ ) of each refractory 4 ₁ (4 ₂ ) are abutted. The height and length of the convex part 4a ₁ (4a ₂ ) and the convex part 4a ₁ (4a ₂ ) of the inlay structure were each 15 mm, and the thickness of the entire refractory was 30 mm. This refractory rises to 1400 ° C. during single crystal growth of lithium tantalate. The used alumina has a coefficient of thermal expansion of 8.0 × 10 ⁻⁶ / K. Therefore, the clearance of the inlay structure was set to 0.2 mm.
When single crystal growth was continuously repeated using the single crystal growth apparatus of Example 1, no single crystal yield reduction was observed up to 100 times. Although deformation of the refractory material was observed, no gas convection from the seam or gaps where light (radiation) leaked were observed.

Example 2
The single crystal growth apparatus of Example 2 was provided with a configuration corresponding to the single crystal growth apparatus of the second embodiment shown in FIG.
Specifically, the joint portion of the alumina refractory disposed at a position covering the crucible is formed of the inclined surface shown in FIG. 4, and the inclined surfaces of the refractory 4 ₁ (4 ₂ ) are abutted with each other. . The length of the base of the right triangle of the cross section at the joint portion of each refractory 4 ₁ (4 ₂ ) composed of the inclined surface was 30 mm, and the inclination angle of the inclined surface with respect to the horizontal plane was 45 °. Moreover, the clearance gap between the seam parts in room temperature was 0.2 mm.
Other configurations were the same as those of the single crystal growth apparatus of Example 1, and single crystal growth was continuously repeated as in Example 1.
When the growth of the single crystal was continuously repeated using the single crystal growth apparatus of Example 2, no decrease in the yield of the single crystal was observed up to 100 times. Although deformation of the refractory material was observed, no gas convection from the seam or gaps where light (radiation) leaked were observed.

Example 3
The single crystal growth apparatus of Example 2 was provided with a configuration corresponding to the single crystal growth apparatus of the second embodiment shown in FIG.
Specifically, the joint portion of the alumina refractory disposed at a position covering the crucible is formed of the inclined surface shown in FIG. 4, and the inclined surfaces of the refractory 4 ₁ (4 ₂ ) are abutted with each other. . The angle of inclination of the inclined surface with respect to the horizontal plane at each joint portion of each refractory 4 ₁ (4 ₂ ) constituted by the inclined surface was 60 °, and the gap between the joint portions at room temperature was 0.2 mm.
Other configurations were the same as those of the single crystal growth apparatus of Example 1, and single crystal growth was continuously repeated as in Example 1.
When the growth of the single crystal was continuously repeated using the single crystal growth apparatus of Example 2, no decrease in the yield of the single crystal was observed up to 100 times. Although deformation of the refractory material was observed, no gas convection from the seam or gaps where light (radiation) leaked were observed.

Comparative Example 1
In the single crystal growth apparatus of Comparative Example 1, the joint portion of the alumina refractory disposed at a position covering the crucible upper portion is perpendicular to each plate-like refractory 4 ₁ (4 ₂ ) as shown in FIG. It was set as the structure which faces each other. In order to prevent gas convection and light (radiation) from leaking from the joints, the joints of the respective plate-like refractories 4 ₁ (4 ₂ ) were arranged so as to have no gaps at room temperature.
Other configurations were the same as those of the single crystal growth apparatus of Example 1, and single crystal growth was continuously repeated as in Example 1.
When the single crystal growth was continuously repeated using the single crystal growth apparatus of Comparative Example 1, a decrease in the yield of the single crystal was observed in the growth of the single crystal after 30 times. While deformation was observed in the refractory, gas convection and light (radiation) leaked from the joint.

Comparative Example 2
In the single crystal growth apparatus of Comparative Example 2, the joint portion of the alumina refractory disposed at a position covering the crucible upper portion has an inlay structure in which the concave portion and the convex portion of each refractory are abutted, and the convex portion of the inlay structure The refractory with one end of the joint located on the lower side: 5 mm, and the other refractory with the end of the joint located on the upper side: 25 mm.
Other configurations were the same as those of the single crystal growth apparatus of Example 1, and single crystal growth was continuously repeated as in Example 1.
When the growth of the single crystal was continuously repeated using the single crystal growth apparatus of Comparative Example 2, a decrease in the yield of the single crystal was observed in the growth of the single crystal after 5 times. Cracks were observed in the convex portion of the inlay structure in one refractory with the tip of the joint located below, and a gap through which gas convection and light (radiation) leaked from the joint was observed.

Comparative Example 3
The single crystal growth apparatus of Comparative Example 3 has a structure in which the joint portion of the alumina refractory disposed at a position covering the crucible is formed of an inclined surface, and the inclined surfaces of the refractories are abutted with each other. The inclination angle with respect to the angle was 10 °.
Other configurations were the same as those of the single crystal growth apparatus of Example 1. And the growth of the single crystal was repeated continuously.
When the single crystal growth was repeated continuously using the single crystal growth apparatus of Comparative Example 3, a decrease in the yield of the single crystal was observed in the growth of the single crystal after 15 times. Cracks were found in part of the tip of the joint in one refractory with the tip of the joint located below, and a gap through which gas convection and light (radiation) leaked from the joint was observed.

Comparative Example 4
The single crystal growth apparatus of Comparative Example 4 has a structure in which the joint portion of the alumina refractory disposed at a position covering the upper portion of the crucible is formed of an inclined surface, and the inclined surfaces of the refractories are abutted with each other. The inclination angle with respect to was 80 °.
Other configurations were the same as those of the single crystal growth apparatus of Example 1, and single crystal growth was continuously repeated.
When the single crystal growth was repeated continuously using the single crystal growth apparatus of Comparative Example 4, a decrease in the yield of the single crystal was observed in the growth of the single crystal after 40 times. While deformation was observed in the refractory, gas convection and light (radiation) leaked from the joint.

  The single crystal production apparatus of the present invention is useful in a field where it is required to repeatedly grow a single crystal industrially using a crystal growth method for growing a single crystal while pulling a seed crystal from a raw material melt.

1 crucible 2 material melt 3 refractory disposed around the crucible 1 4 crucible 1 refractories arranged above the covering position 4 ₁ one refractory 4 ₂ other refractory 4a _1, 4a ₂ convex 4b ₁ , 4b ₂ recess 4H hole 5 heating means (high frequency induction coil)
6 refractory 51 crucible 52 a raw material melt 53 insulating structure ₅₃ 1 forming a support for supporting the chamber 7 seed crystal 8 pulling shaft 9 crucible _1, 53 _2, 53 _3, 53 4, 53 ₅ heat insulating material 54, 55 heater 56 Chamber 57 Seed crystal 58 Pull-up shaft 58a Seed crystal holding part

Claims (4)

A hole used for a crystal growth method for growing a single crystal while pulling up a seed crystal brought into contact with the surface of the raw material melt, and disposed in a position covering the upper part of the crucible to pull up the seed crystal and pass a pulling shaft In a single crystal growing apparatus, a plate-like refractory material having a straight line crossing a hole for passing the pulling shaft is divided,
The joint portion of each of the refractories is such that the tip of the joint portion of one of the refractories is located below the tip of the joint portion of the other refractory, and the joint of the refractories of each other A single crystal growing apparatus characterized in that the upper surface and the lower surface of the portion are opposed to each other, and the flat surfaces are brought into close contact with each other during single crystal growth. The joint portion of each refractory has a concave portion and a convex portion, one concave portion of the refractory and the convex portion of the other refractory, one convex portion of the refractory and the other refractory Is formed in an inlay structure that abuts the recess of
The single crystal growing apparatus according to claim 1, wherein each of the concave portion and the convex portion of each refractory has a height substantially ½ of the thickness of the refractory. The joint part of each of the refractories consists of inclined surfaces, and is formed in a structure in which the inclined surfaces of the refractories of each other face each other.
The single crystal growing apparatus according to claim 1, wherein the inclined surface of the refractory has an inclination angle of 40 ° or more and less than 70 °.   The single crystal growing apparatus according to any one of claims 1 to 3, wherein a tip of a joint portion of the refractory has a corner formed on a C plane or an R plane.

Images