JP6988659B2 - Single crystal growing device - Google Patents

Description

The present invention relates to a single crystal growing apparatus 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.

As a method for growing a single crystal, the Czochralski method, in which a rutsubo filled with a raw material is heated and melted, and then the seed crystal is brought into contact with the surface of the raw material melt and the seed crystal is pulled up to grow the single crystal, has become widespread. There is.

The temperature distribution and temperature gradient in the furnace are important for growing single crystals. In the process of growing a single crystal, a slightly supercooled state is created from the thermal equilibrium state, and the single crystal is grown while releasing the latent heat generated when the raw material melt (liquid) changes to a 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 an industrially usable single crystal.

For example, when the temperature distribution in the furnace is narrow and the distance between the isotherms is narrow and the temperature gradient in the furnace is steep, the temperature control is easy and the latent heat associated with crystallization can be sufficiently released. Therefore, the shape of the single crystal can be easily controlled.
However, the temperature difference inside the growing single crystal becomes large, and due to the thermal strain caused by the thermal expansion of the crystal, crystal defects are introduced and polycrystallization is likely to occur. Further, even if the crystals are not polycrystallized, there arises a problem that the crystal quality is deteriorated due to cracking of the crystal due to thermal strain and crystal defects introduced inside the crystal.

On the other hand, when each isotherm has a wide temperature distribution in the furnace and the temperature gradient in the furnace is gentle, the temperature difference inside the growing single crystal becomes small, which is caused by 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 isotherm distribution of the raw material melt, the growth control of the single crystal is very difficult when the temperature gradient in the furnace is gentle and the distance between the isotherms is wide. It becomes difficult.
For example, the output control range of the heating means in the furnace at the time of growing a single crystal, such as a heating element for resistance heating and an induction heating coil, is narrowed. In addition, the crystal growth becomes sensitive to temperature changes due to changes in the environment around the single crystal growing device and changes in the components inside the device. Then, even if a slight fluctuation in the temperature 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, polycrystallization caused by crystal defects introduced into the crystal and cracking due to the generation of stress-concentrated portions due to a sudden change in crystal shape become problems. Further, since the desired single crystal shape cannot be obtained, when the single crystal is processed into a wafer shape, a portion where the wafer cannot be obtained is generated, and the yield at the time of wafer processing is lowered.

As described above, in growing a single crystal, it is necessary to optimize the temperature distribution and temperature gradient inside the single crystal growing device.
By the way, with respect to the heat insulating structure arranged around the heating element in the single crystal growing apparatus, the present inventor suppresses the radiant heat from the heating element from leaking to the outside through the heat insulating material, and suppresses the leakage to the outside of the heat insulating structure. As a technique capable of suppressing non-uniformity of the temperature distribution in the inner region and a decrease in thermal efficiency, the heat insulating structure described in the following Patent Document 1 was derived.

Japanese Unexamined Patent Publication No. 2016-20254

As shown in FIG. 5A, the technique described in Patent Document 1 is a heat insulating structure 53 arranged around a heating element (heaters 54, 55, rutsubo 51, raw material melt 52), and has a height. a plurality of heat insulating material 53 _{1-53 5} laminated direction, as shown in FIG. 5 (b) in a one heat insulating material 53 of _n adjacent in the height direction, in the other heat insulating material 53 n _{+ 1} Metropolitan , 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 _The recess 53b _{n + 1} corresponding to n is formed. In FIG. 5A, 56 is a chamber, 57 is a seed crystal, 58a is a seed crystal holding portion, 58 is a pull-up shaft, and 59 is a crucible support.
According to the technique described in Patent Document 1, heat insulating materials laminated adjacent to each other in the height direction have concave portions and convex portions, so that radiant heat from a heating element passes between the heat insulating materials due to the side walls of the convex portions. It is possible to prevent leakage to the outside.
For this reason, the present inventors have configured a single crystal growing apparatus using the technique of a heat insulating structure in which heat insulating materials laminated adjacent to each other in the height direction have concave portions and convex portions described in Patent Document 1. By doing so, I thought that it would be possible to optimize the temperature distribution and temperature gradient inside the single crystal growth device.

However, as a result of repeated trial and error, the present inventors have developed a technique of a heat insulating structure described in Patent Document 1 in which heat insulating materials laminated adjacent to each other in the height direction have concave portions and convex portions. In the single crystal growth device used, when the single crystal is grown repeatedly industrially, the yield of the single crystal is maintained by maintaining the optimization of the temperature distribution and temperature gradient inside the single crystal growth device while suppressing the cost. It was found that there are issues that need to be further improved in order to improve.

In view of the above circumstances, the present invention can suppress changes in the temperature distribution and temperature gradient inside the single crystal growing apparatus as much as possible by repeatedly growing the single crystal industrially, and the single crystal yield is high at low cost. It is an object of the present invention to provide a crystal growth apparatus.

In order to achieve the above object, the 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 in contact with the surface of the raw material melt, and is arranged at a position covering the upper part of the rutsubo. In a single crystal manufacturing apparatus in which a plate-shaped refractory material having a hole for pulling up the seed crystal and passing through the pulling shaft is divided at a straight line crossing the hole for pulling up the seed crystal. In each of the seams of the fireproof material, the tip of the seam portion of the fireproof material of one is located below the seam portion of the fireproof material of the other, and the seam portion of the fireproof material of each other is located. It is characterized in that it has planes facing each other on the upper side and the lower side, and the planes are in close contact with each other during single crystal growth.

Further, in the single crystal growing apparatus of the present invention, each of the seams of the refractory has a concave portion and a convex portion, and one of the concave portion of the refractory and the convex portion of the other refractory. The convex portion of the refractory and the concave portion of the other refractory are formed into an inlay structure, and the concave portion and the convex portion of each of the refractory have approximately ½ of the thickness of the refractory. It is preferable to have the height of.

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

Further, in the single crystal growing apparatus of the present invention, it is preferable that the tip of the seam portion of the refractory has a corner portion formed on the C-plane or the R-plane.

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

It is explanatory drawing which shows typically an example of the single crystal growth apparatus which can be applied to embodiment of this invention. In the explanatory view showing the main part configuration of the single crystal growing apparatus according to the first embodiment of the present invention, (a) is a straight line crossing a hole for passing a pulling shaft, which is arranged at a position covering the upper part of the crucible. A perspective view showing the overall configuration of the plate-shaped refractory divided as a boundary, (b) is a perspective view showing the joint portion of one of the divided plate-shaped refractories shown in (a), (c). Is a diagram showing the relationship between the height and length of the convex portion at the joint portion of the plate-shaped refractory shown in (b) and the thickness of the plate-shaped refractory, and (d) is the plate-shaped refractory shown in (c). The figure which shows one deformation example of the corner part of a seam part in a refractory, (e) is the figure which shows the other deformation example of the corner part of a seam part in a plate-shaped refractory shown in (c). It is explanatory drawing which shows the main part structure of the single crystal growth apparatus which concerns on the modification of embodiment of FIG. A perspective view showing the overall configuration of a plate-shaped refractory divided around the boundary, (b) is a side view of (a). In the explanatory view showing the main part configuration of the single crystal growing apparatus according to the second embodiment of the present invention, (a) is a straight line crossing a hole for passing a pulling shaft, which is arranged at a position covering the upper part of the rutsubo. A perspective view showing the overall configuration of the plate-shaped refractory divided as a boundary, (b) is a perspective view showing the joint portion of one of the divided plate-shaped refractories shown in (a), (c). Is a diagram showing the inclination angle of the inclined surface at the seam of the plate-shaped refractory shown in (b), and (d) is a modification of the corner of the seam of the plate-shaped refractory shown in (c). (E) is a diagram showing another deformation example of the corner portion of the seam portion in the plate-shaped refractory shown in (c). It is explanatory drawing which shows schematicly about the heat insulating structure described in Patent Document 1, (a) is the figure which shows the structural example of the single crystal growth apparatus provided with the heat insulating structure, (b) is the heat insulating structure of (a). It is a figure which shows the structure of the heat insulating material contained in. An explanatory diagram showing the configuration of a plate-shaped refractory that is arranged at a position that covers the upper part of the crucible in a conventional single crystal growing device and is divided by a straight line that crosses a hole for passing a pulling shaft. a) is a perspective view showing the overall configuration, (b) is a perspective view showing a joint portion of one of the divided plate-shaped refractories shown in (a), and (c) is a side view of (b). ..

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram schematically showing an example of a single crystal growing apparatus used in the Czochralski method, which is the most common method for producing a single crystal, which can be applied to the embodiment of the present invention.
In the Czochralski method, a single crystal called a seed crystal cut out according to a certain crystal orientation is attached to the tip of a pull-up 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 pull-up 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, the single crystal growing apparatus applicable to the present embodiment includes a crucible 1, a refractory 3 arranged around the crucible 1, and a refractory arranged at a position covering the upper part of the crucible 1. A refractory material constituting an object 4, a pulling shaft 8 provided with a rotation mechanism (not shown), a heating means 5 for heating the crucible 1 (a high-frequency induction coil in the example of FIG. 1), and a support base for supporting the crucible 1. It has a 9. 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 a 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. After that, the seed crystal 7 attached to the tip of the pulling shaft 8 is brought into contact with the surface of the raw material melt 2 while rotating, and the pulling shaft 8 is moved while maintaining the state in which the seed crystal is in contact with the surface of the raw material melt 2. A single crystal is manufactured while gradually pulling up.

However, regarding the refractory material 3 arranged around the crucible 1 in the single crystal growing apparatus having the above configuration, the heat insulating materials laminated adjacent to each other in the height direction described in Patent Document 1 derived by the present invention If a plurality of refractories are laminated in the height direction and the refractories laminated adjacent to each other in the height direction have the concave portions and the convex portions by using the technique of the heat insulating structure having the concave portions and the convex portions. It is possible to suppress the leakage of radiant heat from the raw material melt 2 and the crucible 1 to the outside.

Here, the present inventors consider that if the radiant heat from the raw material melt 2 and the crucible 1 can be suppressed from leaking to the outside, the temperature distribution and temperature gradient inside the single crystal growing apparatus can be maintained in an optimized state. Further, the refractory materials 3 arranged around the crucible 1 are laminated in a plurality of layers in the height direction, and the refractory materials 3 laminated adjacent to each other in the height direction have concave portions and convex portions. An experiment was conducted in which single crystal growth was repeated industrially using a single crystal growth device.

However, when the growth of the single crystal is repeated, the heat insulating materials laminated in the height direction adjacent to each other on the refractory material 3 arranged around the crucible 1 form concave portions and convex portions. It has been found that the problem of lowering the yield of a single crystal occurs due to the gradual deviation of the temperature distribution and temperature gradient inside the single crystal growing device using the technology of the heat insulating structure.

It is considered that the deviation of the temperature distribution and the temperature gradient inside the single crystal growing apparatus is due to the change with time of the components in the furnace generated by the thermal cycle in the single crystal growing process. In the single crystal growth process, the raw material is put into the rutsubo in the furnace at room temperature, and the temperature inside the single crystal growth device is raised for melting the raw material and growing the crystal from the state where the refractory is arranged. As the temperature to be raised at this time, a temperature sufficient for melting the raw material is required. In addition, after the crystal growth is completed, it is necessary to cool the grown single crystal to room temperature again in order to take it out.

In the case of melt growth, the temperature until the raw material installed inside the single crystal growing device 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. Due to the thermal cycle in which the temperature rises from room temperature to a melting point exceeding 1000 ° C. and then lowered to room temperature again, the composition inside the single crystal growing apparatus changes with time. Refractory materials can be considered as the main constituents that change over time.

The material of the refractory is selected according to the operating temperature and atmosphere. By repeating the heat cycle as described above, the refractory material also undergoes a reaction with the atmosphere inside the single crystal growing apparatus and a slight deterioration due to sublimation. Further, the refractory material repeats expansion and contraction. However, as the refractory material, a refractory material having a low thermal conductivity is usually used in order to shield heat. For this reason, a temperature difference occurs inside the refractory in the process of undergoing the thermal cycle in the growth of the single crystal. As a result, by repeating the thermal cycle as described above, thermal strain due to the temperature distribution and temperature gradient inside the refractory is generated, and the refractory is deformed.

Here, the heat insulating structure (refractory) arranged around the crucible described in Patent Document 1 has, for example, a configuration in which a plurality of brick-shaped heat insulating materials (refractory) are stacked in the height direction on the upper part of the crucible. It is thicker than the heat insulating structure (refractory) to be arranged. If the heat insulating materials (refractory) that are laminated adjacent to each other in the height direction with a large thickness have a concave portion and a convex portion, the radiant heat from the heating element is generated between the heat insulating materials (refractory) due to the side wall of the convex portion. It is considered that it is easy to suppress leakage to the outside through.

By the way, the refractory material arranged on the upper part of the rutsubo has a hole 4H for pulling up the seed crystal and passing the pulling shaft as shown in FIG. 6A in order to take out the grown single crystal, and also has a pulling shaft. It is often formed in the shape of a plate divided into two in a substantially semicircular shape in the vertical direction (direction of cutting by a vertical surface) with a straight line crossing the hole 4H for passing through as a boundary.
The reason is that if the refractory material placed on the upper part of the crucible is formed in a plate shape divided by a straight line crossing the hole for passing the pulling shaft, one plate-shaped refractory material should be removed. So, while it is possible to take out a single crystal that has grown to a diameter larger than the diameter of the hole for passing the pulling shaft, if the refractory material arranged on the upper part of the crucible is not divided, the pulling shaft is passed through. This is because a single crystal grown to a diameter larger than the diameter of the crucible cannot be taken out.

However, at the time of derivation of the technique described in Patent Document 1, the present inventor presents that the radiant heat from the heating element in the thick heat insulating structure (refractory) arranged around the crucible passes between the heat insulating materials to the outside. Focusing on suppressing leakage to the crucible, the refractory material placed on the upper part of the crucible is divided into two plates in the vertical direction with a straight line crossing the hole for passing the pulling shaft as a boundary. The problem of deformation due to the formation of the crucible and the problem of deformation due to repeated thermal cycles in the process of growing an industrial single crystal have not been noticed.

The conventional single crystal growing apparatus used in the crystal growing method for growing a single crystal while pulling up the seed crystal brought into contact with the surface of the raw material melt includes a crucible including the single crystal growing apparatus described in Patent Document 1. As shown in FIG. 6 (b), the fireproof material disposed on the upper part is divided into substantially semicircular shapes in the vertical direction with a straight line crossing the hole 4H for passing the pulling shaft as a boundary, and each plate-like material is formed. The structure was such that the vertical surfaces of the fireproof material were butted against each other.

If the refractory material (particularly in the vicinity of the hole 4H for passing the pulling shaft) arranged in the upper part of the crucible having such a structure is deformed, a gap is likely to occur in the joint portion between the refractory materials. When atmospheric gas leaks from this gap, heat outflow occurs due to convection heat transfer. Further, when light leaks, heat outflow occurs due to radiation. Such heat outflow occurs locally from the gap created by the deformation of the refractory. As a result, the temperature distribution and temperature gradient inside the single crystal growing device change locally, the symmetry of the temperature distribution and temperature gradient inside the single crystal growing device is broken, and the yield of the single crystal decreases.

The fireproof material placed on the upper part of the rutsubo has a large amount of heat transfer due to convection heat transfer due to the atmospheric gas flowing out of the system from the vicinity of the hole for passing the pulling shaft when growing a single crystal, and it also heats from the side of the hole. Therefore, the temperature in the vicinity of the hole is the highest, and the temperature is lower toward the periphery. have.
However, as described above, when the present inventors repeated the thermal cycle in the process of growing an industrial single crystal, the refractory material arranged on the upper part of the crucible was particularly near the hole for passing the pulling shaft. However, it was found that it is easily deformed by thermal strain caused by the temperature distribution and temperature gradient in the refractory. When a gap is created in the initially designed seam due to deformation of the refractory material arranged on the upper part of the crucible, convection heat transfer by atmospheric gas and heat outflow due to radiation occur from the gap.
As for the deformation of the refractory material arranged on the upper part of the crucible, for example, as shown in FIGS. 6 (a) and 6 (b), the substantially disc-shaped refractory material 4 crosses the hole 4H for passing the pulling shaft. _{In the case of a configuration in which the refractory 4 1} and the refractory 4 ₂ are vertically divided into two with the straight line as the boundary, the hole 4H for passing the pull-up shaft located in the center of the circle which is the outer shape of the refractory 4. Since the joint portion in the vicinity is located in the center of the upper part of the crucible, the temperature tends to be high and the deformation becomes large. As for the deformation of this part, the pull-up shaft located in the center of the circle tends to warp upward in the vicinity of the hole 4H for passing the pull-up shaft located in the center of the circle due to heat from below. A gap is created in the vicinity of the hole 4H for passing.

If the refractory material arranged on the upper part of the crucible is deformed, the yield of the single crystal is lowered, so that it is necessary to replace the refractory material arranged on the deformed upper part of the crucible. However, if the number of times of repeating the thermal cycle in the industrial single crystal growing process until the refractory material disposed on the upper part of the crucible is deformed is small, the replacement cost of the refractory material becomes high.

However, at the time when the present inventor has derived the technique described in Patent Document 1, as described above, the refractory material arranged on the upper part of the rutsubo is in the vertical direction with the straight line crossing the hole for passing the pulling shaft as a boundary. Attention has been paid to the problem of deformation due to the formation of a plate divided into two in a substantially semicircular shape, and the problem of deformation due to repeated thermal cycles in the process of growing an industrial single crystal. I wasn't.
As a result of repeated trial and error, the present inventors have used the technique of a heat insulating structure described in Patent Document 1 in which heat insulating materials laminated adjacent to each other in the height direction have concave portions and convex portions. The single crystal growth device maintains the optimization of the temperature distribution and temperature gradient inside the single crystal growth device while suppressing the cost when growing the single crystal repeatedly industrially, and improves the yield of the single crystal. We found that there were inherent issues that needed to be further improved.

Therefore, the present inventors tend to warp the vicinity of the hole for passing the refractory shaft located at the center of the circle upward due to the deformation of the refractory material arranged on the upper part of the crucible. As a means to prevent a gap from forming even if the vicinity of the hole for passing is warped upward, the joint of each refractory is divided with a straight line crossing the hole for passing the pulling shaft as a boundary. The tip of the seam of one refractory is located below the seam of the other refractory, and has planes facing each other on the upper and lower sides of the seam of each refractory. We have come up with the idea of the configuration of the single crystal growing apparatus of the present invention, which has a structure in which the planes are in close contact with each other during single crystal growing.

1st Embodiment FIG. 2 is an explanatory view which shows the main part structure of the single crystal growing apparatus which concerns on 1st Embodiment of this invention, (a) is for passing a pulling shaft arranged at the position which covers the upper part of a refractory. A perspective view showing the overall configuration of a plate-shaped refractory divided with a straight line crossing the hole as a boundary, (b) shows the joint portion of one of the divided plate-shaped refractories 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-shaped refractory shown in (b) and the thickness of the plate-shaped refractory, (d) is (d). The figure showing one modification of the corner of the seam in the plate-shaped refractory shown in c), (e) is another modification of the corner of the seam in the plate-shaped refractory shown in (c). It is a figure which shows. FIG. 3 is an explanatory view showing a main configuration of a single crystal growing device according to a modified example of the embodiment of FIG. 2, and FIG. 3A shows a hole for passing a pulling shaft arranged at a position covering the upper part of the crucible. A perspective view showing the overall configuration of a plate-shaped refractory divided with a crossing straight line as a boundary, (b) is a side view of (a). In the figure used in the embodiment of the present invention, for convenience, it corresponds to the technique of the heat insulating structure in which the heat insulating materials laminated adjacent to each other in the height direction have concave portions and convex portions, which is described in Patent Document 1. , The configuration of the portion where the refractory material 3 and the refractory material 4 are laminated in the height direction is omitted.

In single crystal growing apparatus of the present embodiment, FIG. 2 (a), the as shown in FIG. 2 (b), the joint portion of the refractory of the respective 4 _{1 (4 2),} the recess 4b 1 and _{(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)} approximately half the height of the thickness (tx) (hb ≒ 1 / 2tx, ha ≒ 1 / 2tx) and having a refractory ₄ 1 _{(4 2)} 0.4 times to 0.6 times the thickness of the Has a length of (Lb = (0.6 to 0.4) tx, La = (0.4 to 0.6) tx).
Then, another refractory ₄ 1 _{(4 2)} has a plane face on the upper side and lower side of the recess _4b 1 (4b ₂₎ and the protrusions _4a 1 (4a _2), in the upper and lower The planes facing each other are arranged so as to be in close contact with each other 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 each other on the upper side and the lower side are brought into close contact with each other during single crystal growth, the concave portions 4b ₁ (4b ₂ ) and the convex portions 4a ₁ (4a ₂ ) of the refractory are brought into close contact with each other, so that the refractory is a refractory. vertical hole 4H vicinity for passing the pulling shaft in the center portion even if deformation warped upward, the convex portion 4a ₁ of the one of the refractory 4 ₁ the front end of the seam section is positioned below the Since the plane in the direction overlaps with the vertical plane of the recess 4b _{2 in the other refractory 4 2} where the tip of the seam is located on the upper side over the length of the _{protrusion 4a 1, gas convection occurs.} It can block and prevent light (radiation) leakage.

Incidentally, the refractory of each of the single crystal growing apparatus of the present embodiment ₄ 1 _{(4 2)} recess _4b 1 which forms a spigot structure seam portion (4b ₂₎ and the protrusions _4a 1 (4a ₂₎ includes an upper It is important to have planes facing each other on the lower side and to arrange the planes facing each other on the upper side and the lower side so as to be in close contact with each other during single crystal growth. If there is a gap in this flat surface portion, gas convection can be blocked and light (radiation) leakage cannot be prevented.
On the contrary, it is preferable to provide a gap between the vertical seams of the tips _{of the convex portions 4a 1} (4a _{2 ) (the roots of the concave portions 4b 1} (4b _{2)) at room temperature.} The gap between the joints 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, when the refractory thermally expands due to the temperature rise during heating, the vertical seams (especially the seams near the crucible) ) Is overstressed, which may cause misalignment or damage to the refractory. Therefore, in consideration of the amount of thermal strain at the operating temperature of the refractory, it is preferable to have a structure in which there is a gap between the joints in the vertical direction as shown in FIGS. 3 (a) and 3 (b) at room temperature. ..
In the examples of FIGS. 3 (a) and 3 (b), the planes facing each other on the upper side and the lower side in _{the concave portion 4b 1} (4b ₂ ) and the convex portion 4a ₁ (4a _{2) have a gap at room temperature.} However, it is configured to be in close contact 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 ) The structure has a height (hb≈1 / 2tx, ha≈1 / 2tx) approximately 1/2 times the thickness (tx), and the upper and lower portions of each refractory are in close contact with each other. Since the thickness of the refractory is made substantially uniform, it is possible to prevent severe deformation of only one of the refractory joints, cracking or breakage of the convex portion, or generation of a gap. This effect is known as a result of trial and error by the present inventors regarding the heights of the concave portions 4b ₁ (4b ₂ ) and the convex portions 4a ₁ (4a _{2 ) of each other's refractories 4a 1} (4a _2). I got it.

If the recesses and protrusions of each refractory are not configured to have a height of approximately 1/2 the thickness of the refractory, the refractory with the tip of the seam located on the lower side and the refractory. The thickness of the overlapping portion differs between the upper side and the lower side of the other refractory whose tip of the seam is located on the upper side.
However, when the thickness of the overlapping portion is different between the upper side and the lower side, the joint portion of one of the refractories is severely deformed, and the convex portion is cracked or damaged, or the gap between the concave portion and the convex portion is generated. Is more 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) With a configuration having a length (Lb = (0.6 to 0.4) tx, La = (0.4 to 0.6) tx) of 0.4 to 0.6 times the thickness (tx) of Therefore, even if the refractory is deformed, it becomes easy to prevent the generation of gaps in the flat portion in the concave portion and the convex portion, and the cracking or breakage of the convex portion.
If the length of the concave and convex portions of each refractory is less than 0.4 times the thickness of the refractory, a gap is likely to occur in the flat surface portion 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, the thermal stress increases, and the amount of deformation of the refractory increases. Therefore, the length of the concave portion and the convex portion of each refractory must be 0.4 times or more the thickness of the refractory, and the thicker the refractory, the longer it is preferable.
However, if the length of the concave and convex portions of each refractory exceeds 0.6 times the thickness of the refractory, the tip of the seam will be located on the lower side of the refractory when the refractory is deformed. The convex part in the above is too restrained in contact with the concave part of the other refractory whose tip of the seam is located on the upper side, and a large stress is generated, and the tip of the seam is located on the lower side of the refractory. There is a risk that the convex part of the object will crack.
Therefore, the single crystal growing apparatus of the present embodiment, preferably, the length Lb of the recess _4b 1 of each of the refractories _{4 1 (4 2) (4b} 2) and the protrusions _4a 1 _{(4a 2),} La is It is preferable that the length is 0.5 times the thickness of the refractory (Lb = 0.5tx, La = 0.5tx).

The tip of the convex portion constituting the seam portion is easily chipped. In particular, in the convex portion of one refractory whose tip of the seam is located on the lower side, the corner portion on the side near the root of the concave portion of the other refractory whose tip of the seam is located on the upper side is the refractory. Stress is concentrated at the time of deformation, and chipping is likely to occur.
Therefore, in the single crystal growing apparatus of the present embodiment, it is preferable that the corner portion of the tip of the joint portion of the refractory (particularly, the convex portion of the _{one refractory 41 whose tip is located on the lower side).} As shown in FIGS. 2 (d) and 2 (e), the corners of _{4a 1} near the root of the recess 4b _{2 of the other refractory 4 2} in which the tip of the seam is located on the upper side). , It is desirable to have a configuration formed on the C surface or the R surface.

2nd Embodiment FIG. 4 is an explanatory view which shows the main part structure of the single crystal growing apparatus which concerns on the 2nd Embodiment of this invention, (a) is for passing the pulling shaft arranged at the position which covers the upper part of a rut. A perspective view showing the overall configuration of a plate-shaped refractory divided with a straight line crossing the hole as a boundary, (b) shows the joint portion of one of the divided plate-shaped refractories shown in (a). The perspective view shown, (c) is a diagram showing the inclination angle of the inclined surface in the joint portion of the plate-shaped refractory shown in (b), and (d) is the joint portion in the plate-shaped refractory shown in (c). It is a figure which shows one deformation example of the corner part of, (e) is a figure which shows the other deformation example of the corner part of the seam part in the plate-shaped refractory shown in (c).
In the single crystal growing apparatus of the present embodiment, as shown in FIG. 4A, the seams of the respective refractories 4 ₁ (4 ₂ ) are formed of inclined surfaces, and each refractory 4 ₁ (4 _{2) is formed.} ) Is formed in a structure in which the inclined surfaces are butted against each other.
The inclined surface ₄ 1 of the refractory _{(4 2),} as shown in FIG. 4 (c), has an inclined angle less than 70 ° 40 ° or more with respect to the horizontal plane (30 ° ≦ αx <70 ° ).

Seam portion of the refractory of the respective in single crystal growing apparatus 4 _{1 (4 2)} of the present embodiment has a small thickness of the refractory is the optimal structure when spigot structure as in the first embodiment is difficult ..
This joint has a structure in which right triangles are inverted and abutted when viewed from the side, and the hypotenuses are brought into contact with each other. Therefore, even if the refractory is deformed, as long until a portion corresponding to the length Lc of the base of the right triangle shown in FIG. 4 (c), contact the inclined surfaces of each other refractory 4 _{1 (4 2)} In this state, it is possible to block gas convection and prevent light (radiation) leakage.

Then, according to the single crystal growing apparatus of the present embodiment, the inclination angle of the inclined surface constituting the seam portion of each of the refractories 4 _{1 (4 2),} less than 70 ° 40 ° or more with respect to the horizontal plane (30 ° 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 easier to prevent damage to the tip.

If the angle of inclination of the inclined surface of the refractory exceeds 70 °, there is a high possibility that a gap will be formed at the seam when the refractory is deformed.
On the other hand, when the inclination angle of the inclined surface of the refractory is less than 40 °, when the refractory is deformed, the inclined surface of the _{one refractory 41 whose tip of the seam is located on the lower side is the seam. The state of contact with the inclined surface of the other refractory 4 2} whose tip is located on the upper side is excessively restrained and a large stress is generated, and the seam of the refractory 4 _{1 whose tip is located on the lower side is excessively restrained.} The lower tip of the part may crack.
Therefore, in the single crystal growing apparatus of the present embodiment, preferably, when the inclination angle of the inclined surface of the refractory is 45 °, the inclined surface in _{one of the refractory 41 where the tip of the seam is located 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 easily prevent breakage of the tip of the seam section in one of the refractory 4 _1.

It should be noted that the tip of the seam portion formed of the inclined surface is sharp and easily chipped. 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 corner portion at the tip of the eye portion is formed on the C surface or the R surface. Further, when the edge of the distal end of the seam portion of the refractory of the respective is formed on the C plane or R plane, we have a gap in the vicinity of the distal end of the seam section in each other refractory 4 _{1 (4 2)} Also, as in the gap between the vertical seams at the tips of the protrusions (roots of the recesses) in the inlay structure that constitutes the seams of the single crystal growing apparatus of the first embodiment, due to the temperature rise during heating. It is possible to prevent misalignment and damage of the refractory due to excessive stress applied to the seams having an inclination angle (particularly, the seams near the rutsubo) when the refractory thermally expands. can.

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

Example 1
The single crystal growing apparatus of Example 1 is provided with a configuration corresponding to the single crystal growing apparatus of the first embodiment shown in FIGS. 2 and 3.
The procedure for growing the lithium tantalate single crystal was as follows. At room temperature, the crucible 1 made of iridium is filled with the raw material 2 of lithium tantalate, and the crucible 1 is heated by the 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 vertically pulling the iridium pulling shaft 8 at a speed of 1 to 5 mm / h while rotating the pulling shaft 8 at 1 to 20 rpm. .. After the growth of the single crystal is completed, the temperature is gradually lowered to room temperature, and then the grown single crystal is taken out.
In Example 1, such growth of a single crystal was continuously repeated.

In the single crystal growing apparatus of Example 1, the refractory material arranged at the position covering the upper part of the crucible was made of alumina. The disc-shaped refractory was divided into two, and two semi-circular refractories were used in combination. Seam section, similar to that shown in FIG. 2, was spigot structure to match the mutual refractory ₄ 1 recess _4b 1 of the _{(4 2)} (4b ₂₎ and convex portions _4a 1 (4a _2). The height and length of the convex portions 4a ₁ (4a ₂ ) and the convex portions 4a ₁ (4a ₂ ) of the inlay structure were set to 15 mm, respectively, and the thickness of the entire refractory was set to 30 mm. This refractory rises to 1400 ° C. during the growth of a single crystal of lithium tantalate. The coefficient of thermal expansion of the alumina used is 8.0 × 10 ^-6 / K. Therefore, the gap of the inlay structure is set to 0.2 mm.
When the single crystal growth was continuously repeated using the single crystal growth apparatus of Example 1, no decrease in the yield of the single crystal was observed up to 100 times. Deformation of the refractory was observed, but no gaps for gas convection or light (radiation) leakage from the seams were observed.

Example 2
The single crystal growing apparatus of Example 2 was provided with a configuration corresponding to the single crystal growing apparatus of the second embodiment shown in FIG.
For more information, becomes the joint portion of the alumina refractories arranged at a position covering the crucible upward from the inclined surface shown in FIG. 4, has a structure to match the inclined surfaces of each other refractory 4 _{1 (4 2)} .. With a 30mm length of the base of the cross-section of a right triangle at the seams of the formed respective refractory 4 _{1 (4 2)} the inclined surface, and the inclination angle relative to the horizontal plane of the inclined surface and 45 °. Further, the gap between the seams at room temperature was set to 0.2 mm.
Other configurations were the same as those of the single crystal growing apparatus of Example 1, and the growing of single crystals was continuously repeated as in Example 1.
When the single crystal growth 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. Deformation of the refractory was observed, but no gaps for gas convection or light (radiation) leakage from the seams were observed.

Example 3
The single crystal growing apparatus of Example 2 was provided with a configuration corresponding to the single crystal growing apparatus of the second embodiment shown in FIG.
For more information, becomes the joint portion of the alumina refractories arranged at a position covering the crucible upward from the inclined surface shown in FIG. 4, has a structure to match the inclined surfaces of each other refractory 4 _{1 (4 2)} .. With a 60 ° angle of inclination relative to the horizontal plane of the inclined surface of the seams of the formed respective refractory 4 _{1 (4 2)} the inclined surface, and a 0.2mm clearance between the joint portion at room temperature.
Other configurations were the same as those of the single crystal growing apparatus of Example 1, and the growing of single crystals was continuously repeated as in Example 1.
When the single crystal growth 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. Deformation of the refractory was observed, but no gaps for gas convection or light (radiation) leakage from the seams were observed.

Comparative Example 1
Apparatus for growing a single crystal of Comparative Example 1, perpendicular in the seam portion of the alumina refractories arranged at a position covering the crucible upward as shown in FIG. 6, a plate-like refractory respective 4 _{1 (4 2)} The structure is such that the faces are butted against each other. To prevent gas convection or light (radiation) from leaking through the joint portion, is disposed so that there is no gap in the seam portions of the plate-like refractory respective 4 _{1 (4 2)} at room temperature.
Other configurations were the same as those of the single crystal growing apparatus of Example 1, and the growing of single crystals 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 1, a decrease in the yield of the single crystal was observed in the growth of the single crystal after 30 times. Deformation was observed in the refractory, and there were gaps where gas convection and light (radiation) leaked from the seams.

Comparative Example 2
The single crystal growing device of Comparative Example 2 has an in-row structure in which the joint portion of the alumina refractory arranged at a position covering the upper part of the crucible has an in-row structure in which the concave portion and the convex portion of each refractory are butted against each other, and the convex portion of the in-row structure. The height of the refractory was set to 5 mm for one refractory whose tip of the seam is located on the lower side and 25 mm for the other refractory whose tip of the seam is located on the upper side.
Other configurations were the same as those of the single crystal growing apparatus of Example 1, and the growing of single crystals was continuously repeated as in Example 1.
When the single crystal growth 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 found in the convex part of the inlay structure in one refractory whose tip was located on the lower side of the seam, and there was a gap where gas convection and light (radiation) leaked from the seam.

Comparative Example 3
The single crystal growing device of Comparative Example 3 has a structure in which the seams of the alumina refractories arranged at positions covering the upper part of the crucible are made of inclined surfaces and the inclined surfaces of the refractory are abutted against each other, and the horizontal plane of the inclined surfaces is formed. The inclination angle with respect to the relative angle was set to 10 °.
Other configurations were the same as those of the single crystal growing apparatus of Example 1. Then, the growth of the single crystal was continuously repeated.
When the single crystal growth was continuously repeated 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. A crack was found in a part of the tip of the seam in one refractory whose tip is located on the lower side of the seam, and a gap was observed in which gas convection and light (radiation) leaked from the seam.

Comparative Example 4
The single crystal growing device of Comparative Example 4 has a structure in which the seams of the alumina refractories arranged at positions covering the upper part of the crucible are made of inclined surfaces and the inclined surfaces of the refractory are abutted against each other, and the horizontal plane of the inclined surfaces is formed. The inclination angle with respect to the relative angle was set to 80 °.
Other configurations were the same as those of the single crystal growing apparatus of Example 1, and the growing of single crystals was continuously repeated.
When the single crystal growth was continuously repeated 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. Deformation was observed in the refractory, and there were gaps where gas convection and light (radiation) leaked from the seams.

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

1 Crucible 2 Raw material melt 3 Refractory arranged around the crucible 4 Refractory arranged at a position covering the upper part of the crucible 4 ₁ One refractory 4 _{2 The} other refractory 4a ₁ , 4a ₂ Convex Part 4b ₁ , 4b ₂ Concave 4H Hole 5 Heating means (high frequency induction coil)
6 Chamber 7 Seed crystal 8 Pull-up shaft 9 Refractory forming a support base for crucible 1 Crucible 52 Raw material melt 53 Insulation structure 53 ₁ , 53 ₂ , 53 ₃ , 53 ₄ , _{5 5} Insulation material 54, 55 Heater 56 Chamber 57 Seed crystal 58 Pull-up shaft 58a Seed crystal holder

Claims (4)

It is used in a crystal growth method to grow a single crystal while pulling up a seed crystal that is in contact with the surface of the raw material melt, and is arranged at a position that covers the upper part of the crucible. In a single crystal growing apparatus in which a plate-shaped refractory material having a crucible is divided with a straight line crossing a hole for passing the pulling shaft as a boundary.
In each of the refractory seams, the tip of one of the refractory seams is located below the tip of the other refractory seam, and the seams of each other of the refractories. A single crystal growing device characterized by having planes facing each other on the upper side and the lower side in a portion, and the planes are in close contact with each other during single crystal growing. Each of the refractory joints has a concave portion and a convex portion, one of the concave portion of the refractory and the convex portion of the other refractory, and one convex portion of the refractory and the other of the refractory. Formed in an in-row structure that abuts against the recesses of
The single crystal growing apparatus according to claim 1, wherein each of the concave portion and the convex portion of the refractory has a height of approximately ½ of the thickness of the refractory. The seams of each of the refractories are formed of inclined surfaces, and are formed in a structure in which the inclined surfaces of the refractories are abutted against 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 the tip of the seam portion of the refractory has a corner portion formed on a C-plane or an R-plane.

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