JP2023132267A - Apparatus and method for growing oxide single crystal - Google Patents

Abstract

To provide an apparatus and a method for growing an oxide single crystal, using an oxide crucible formed of the same material as a raw material melt as storing and holding means of the raw material melt.SOLUTION: An apparatus for growing an oxide single crystal includes: an oxide crucible 1 constituted of an oxide crystal material and capable of storing and holding a raw material melt 10; a high frequency induction coil 2 provided around a side wall of the oxide crucible; and a cylindrical metal heater 3 built in the oxide crucible, inductively heated by the coil and including a lower end part 3a fitted to an inner bottom surface 1a of the oxide crucible. A lower end part 2a of the coil is arranged above from the lower end part 3a of the cylindrical metal heater; the lower end part 2a of the coil positioned above from the lower end part 3a of the cylindrical metal heater and the lower end part 3a having a structure preventing induction heating can stably fix the cylindrical metal heater in the oxide crucible, and prevention of the oxide crucible and cylindrical metal heater from being deformed has an effect capable of repeatedly and stably growing an oxide single crystal having same quality.SELECTED DRAWING: Figure 1

Description

The present invention relates to improvements in a growth apparatus and method for growing oxide single crystals such as lithium tantalate by a pulling method.

As a method for growing an oxide single crystal, a crucible filled with raw materials to become an oxide single crystal is heated to a high temperature to melt the raw materials, and a seed crystal is brought into contact with the raw material melt surface in the crucible from above. A pulling method (also referred to as the Czochralski method) is widely used in which an oxide single crystal is grown in the same direction as the seed crystal by raising the crystal while rotating it.

In the apparatus for growing an oxide single crystal using the pulling method, as shown in FIG. An eddy current is generated in the crucible 100, which causes the crucible 100 to generate heat and melt the raw material. Additionally, as the pulling progresses, the upper part of the oxide single crystal is cooled down through the seed rod (crystal pulling shaft) 102, but if the only heating element is the crucible 100, the temperature distribution within the single crystal during growth is large. Therefore, a metal ring-shaped reflector 103 is placed at the open end of the crucible 100, and a metal after-heater 104 is placed at the upper end of the crucible 100. In FIG. 7, 105 is a seed crystal, 106 is a raw material melt, 107 and 108 are heat insulating materials, 109 is a CP crucible (porous alumina crucible), and 110 is a heat insulating crucible stand. .

Incidentally, in recent years, the market for oxide single crystals, particularly lithium tantalate, as a surface acoustic wave device material has been expanding, and the pulled length and diameter of single crystals are gradually increasing in order to secure production volume. Along with this increase in size, crucibles used for crystal growth are also becoming larger.

In addition, the crucible must be conductive to allow high-frequency current to flow through it, and in order to melt the crystal raw material, it must be made of a material with a high melting point that can withstand high temperatures and that will not deteriorate in an oxidizing atmosphere. The crucible used is often made of noble metals such as iridium, platinum, rhodium, etc., or alloys thereof.

However, when a single crystal is grown using a noble metal crucible, there is a problem in that the crucible is deformed. This is because the cylindrical noble metal crucible 100 shown in FIG. 8(A) expands as shown in FIG. 8(B) when the raw material is melted, and when cooled, the solidified portion of the raw material melt 106 expands as shown in FIG. 8(C). This is because the noble metal crucible and the oxide melt have different expansion coefficients.

Therefore, in Patent Document 1, a noble metal crucible is proposed in which a reinforced precious metal plate made of the same material as the crucible and to which zirconium oxide is added is reinforced by closely adhering to the outer periphery of the crucible body, and Patent Document 2 has proposed a growth device in which the crucible is covered with a cylindrical heat insulating material such as alumina to suppress deformation of the crucible. Further, in Patent Document 3, a crucible for single crystal growth is proposed in which a ring-shaped frame is fitted into the outer peripheral surface of the crucible side wall to prevent deformation, and in Patent Document 4, the plate thickness on the bottom side of the crucible is An iridium crucible has been proposed that has a structure that allows deformation to escape to the bottom side by making the crucible thinner than the plate thickness of .

However, even if any of the measures proposed in Patent Documents 1 to 4 is taken, it is difficult to prevent crucible deformation, and in particular, when growing large oxide single crystals, the amount of crucible deformation becomes large, so it is difficult to prevent crucible deformation. countermeasures were required.

Japanese Patent Application Publication No. 10-338593 Japanese Patent Application Publication No. 2020-164339 JP2019-112240A Japanese Patent Application Publication No. 2012-250874

As long as the noble metal crucible is used as a storage and holding means for the raw material melt, deformation cannot be suppressed, so a means for storing and holding the raw material melt in place of the noble metal crucible is required.

The present invention has been made in view of these problems, and its object is to develop an oxidation method using an oxide crucible made of the same material as the raw material melt as a storage and holding means for the raw material melt in place of a precious metal crucible. An object of the present invention is to provide a growing device and method for growing single crystals.

That is, the first invention according to the present invention is
In an apparatus for growing oxide single crystals by the pulling method,
an oxide crucible made of the crystalline material and capable of storing and holding a raw material melt;
a high frequency induction coil provided around the side wall of the oxide crucible;
a cylindrical metal heater that is incorporated into the oxide crucible, is heated by induction by the high-frequency induction coil, and whose lower end is inserted into the inner bottom surface of the oxide crucible;
Further, the lower end of the high frequency induction coil is located above the lower end of the cylindrical metal heater.

Moreover, the second invention according to the present invention is
In the oxide single crystal growth apparatus according to the first invention,
The lower open part of the cylindrical metal heater is closed or a ring-shaped flat part is formed in the lower open part,
The third invention is
In the oxide single crystal growth apparatus according to the first invention or the second invention,
The oxide single crystal is any one of a lithium niobate single crystal, a lithium tantalate single crystal, and a yttrium aluminum garnet single crystal,
The fourth invention is
In the oxide single crystal growth apparatus according to any one of the first to third inventions,
The cylindrical metal heater is made of platinum, iridium, rhodium, or an alloy thereof,
The fifth invention is
In the oxide single crystal growth apparatus according to any one of the first to fourth inventions,
It is characterized by comprising a ceramic container that covers the outer bottom surface of the oxide crucible, or a ceramic crucible that covers the outer bottom surface and side walls of the oxide crucible.

Next, the sixth invention according to the present invention is:
In the method of growing an oxide single crystal using the growth apparatus according to the first invention,
A crystal raw material is put into an oxide crucible with a built-in cylindrical metal heater, and the cylindrical metal heater is heated by induction using a high-frequency induction coil to separate the crystal raw material existing inside the cylindrical metal heater and the cylindrical metal heater. This method is characterized by melting the crystal raw material existing outside the cylindrical metal heater, and growing an oxide single crystal by a pulling method by bringing a seed crystal into contact with the surface of the raw material melt inside a cylindrical metal heater.

According to the oxide single crystal growth apparatus according to the present invention,
The lower end of the high-frequency induction coil is located above the lower end of the cylindrical metal heater, making it difficult for the lower end of the cylindrical metal heater to be heated by induction. It becomes possible to stably fix the cylindrical metal heater in the oxide crucible by inserting it into the inner bottom surface of the crucible.

In addition, since an oxide crucible made of the same material as the raw material melt is used as a storage and holding means for the raw material melt, it is possible to suppress deformation of the crucible. The cylindrical metal heater except for the lower end and its vicinity is heated by induction, so when growing an oxide single crystal, the raw material melt present inside the cylindrical metal heater and the material melt present outside the cylindrical metal heater are heated by induction. The cylindrical metal heater is sandwiched between the raw material melt, and thermal deformation of the cylindrical metal heater can also be suppressed.

Therefore, even if crystal growth is repeated, it is possible to prevent changes in the growth conditions due to fluctuations in the fixed cylindrical metal heater or deformation of the crucible, so that oxide single crystals of the same quality can be repeatedly and stably grown. This has the effect of making it possible.

FIG. 1 is an explanatory diagram of the configuration of a growing device according to the present invention. FIG. 1 is an explanatory diagram of a growing device according to a first embodiment and a growing method using this device. An explanatory diagram of a growing device according to a modification of the first embodiment. Explanatory diagram showing the manufacturing process of the growth device according to the second embodiment. Explanatory diagram showing the manufacturing process of the growth device according to the second embodiment. An explanatory diagram of a growing device according to a second embodiment. FIG. 2 is an explanatory diagram of a growth method using a conventional growth apparatus that uses a noble metal crucible as a storage and holding means for a raw material melt. Figure 8 (A) is a cross-sectional view of the noble metal crucible, Figure 8 (B) is a cross-sectional view of the noble metal crucible when the input crystal raw material is melted, and Figure 8 (C) is the precious metal that has been deformed as the raw material melt solidifies. A cross-sectional view of a crucible.

Hereinafter, embodiments of the present invention will be described in detail using the drawings.

1. Conventional growth device and growth method (1) Conventional growth device and growth method using this device As described above, the conventional growth device includes a CP crucible (porous alumina crucible) in the chamber 200 (see FIG. 7). ) 109, a crucible 100, a heat-insulating crucible stand 110, a ring-shaped reflector 103, an after-heater 104, heat insulators 107 and 108, a seed rod (crystal pulling shaft) 102, and a high-frequency induction coil 101. It has been known. The crucible 100 used for high-temperature crystal growth is a high melting point metal crucible such as tungsten or tantalum, a noble metal crucible such as platinum, rhodium or iridium, or a crucible of alumina, magnesia, carbon or PBN (Pyrolytic Boron Nitride). Non-metallic crucibles are known.

By the way, lithium niobate (LiNbO ₃ : hereinafter abbreviated as LN), lithium tantalate (LiTaO ₃ : hereinafter abbreviated as LT), yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ : hereinafter abbreviated as YAG) When growing oxide single crystals such as oxides, the growth atmosphere contains oxygen, so tungsten, tantalum, and carbon, which are easily oxidized, cannot be used. Similarly, alumina and magnesia cannot be used because they react with the oxide melt, and PBN is expensive and difficult to prepare in large crucibles.

For this reason, when growing oxide single crystals, crucibles of noble metals such as platinum, rhodium, and iridium are used, which are not oxidized and do not crack and cause the raw material melt to flow out.

(2) Conventional issues However, as shown in Figures 8 (A) to (C), noble metal crucibles thermally expand when raw materials are melted, and when the residue of the raw material melt solidifies, the thermal expansion coefficient of the oxide and precious metal increases. are deformed because they are different. Due to this deformation, in the case of high-frequency induction heating, the heat generation state changes, so the growth conditions change, and as the crucible deforms, a single crystal cannot be obtained.

2. Growth apparatus and growth method of the present invention The growth apparatus of the present invention using the pulling method (Czochralski method) is capable of growing oxides such as LN, LT, and YAG in the air or in an inert gas atmosphere containing oxygen. This is a device used to manufacture single crystals. In the Czochralski method, the tip of a single crystal, called a seed crystal, cut out along a certain crystal orientation and usually processed into a rod shape, is soaked in a raw material melt of the same composition and gradually pulled up while rotating. This is a method of growing a single crystal with the same crystal orientation.

In order to solve the conventional problems, the present inventor developed an oxide single crystal growth device and a growth device using an oxide crucible made of the same material as the raw material melt as a storage and holding means for the raw material melt in place of the deformable noble metal crucible. I found a way.

That is, the growing device according to the present invention, as shown in FIG.
An oxide crucible 1 made of an oxide crystal material and capable of storing and holding a raw material melt 10;
a high frequency induction coil 2 provided around the side wall of the oxide crucible 1;
A cylindrical metal heater 3 is installed in the oxide crucible 1, is heated by induction by the high-frequency induction coil 2, and has a lower end 3a inserted into the inner bottom surface 1a of the oxide crucible 1.
Further, the lower end 2a of the high frequency induction coil 2 is located above the lower end 3a of the cylindrical metal heater 3.

(1) Growing device according to the first embodiment and growing method using this device (1-1) Growing device according to the first embodiment The growing device according to the first embodiment has a bottom surface as shown in FIG. The side is fixed with a support stand 11, and the growth apparatus according to the present invention (comprising an oxide crucible 1 and a cylindrical metal heater 3) excluding the high-frequency induction coil 2 is accommodated, and a seed rod (crystal pulling shaft) is installed on the upper side. 20, a ring-shaped reflector 15 placed on the upper end 3b of the cylindrical metal heater 3, and an after-heater 16 placed on the ring-shaped reflector 15. The main part is constituted by a rod-shaped seed crystal 21 attached to the lower end side of the seed rod (crystal pulling shaft) 20. In FIG. 2, reference numeral 4 indicates a ceramic container that covers the outer bottom surface 1b of the oxide crucible 1.

(1-2) Growth method according to the first embodiment A crystal raw material is introduced into an oxide crucible 1 in which a cylindrical metal heater 3 is incorporated, and the cylindrical metal heater 3 is heated by induction using a high frequency induction coil 2. The crystal raw material present inside the cylindrical metal heater 3 and the crystal raw material present outside the cylindrical metal heater 3 are melted.

Next, after bringing the seed crystal 21 into contact with the surface of the raw material melt 10 in the cylindrical metal heater 3, the seed rod (crystal pulling shaft) 20 is raised while rotating to grow the oxide single crystal 30.

(1-3) Effects of the first embodiment According to the growth device according to the first embodiment, the lower end 2a of the high-frequency induction coil 2 is located above the lower end 3a of the cylindrical metal heater 3, and the cylindrical metal Since the lower end 3a of the heater 3 has a structure that is difficult to be heated by induction, the lower end 3a of the cylindrical metal heater 3 is inserted into the inner bottom surface 1a of the oxide crucible 1, and the cylindrical metal heater 3 is inserted into the oxide crucible. It can be stably fixed within 1.

Since the oxide crucible 1 made of the same material as the raw material melt is used as a storage and holding means for the raw material melt, deformation of the crucible can be suppressed, and furthermore, the oxide crucible 1 can be inserted into the inner bottom surface 1a of the oxide crucible 1. Since the portion of the cylindrical metal heater 3 excluding the lower end portion 3a and its vicinity is heated by induction, the raw material melt 10 existing inside the cylindrical metal heater 3 and the cylinder are heated during the growth of the oxide single crystal. The cylindrical metal heater 3 is sandwiched between the raw material melt 10 existing outside the cylindrical metal heater 3, and thermal deformation of the cylindrical metal heater 3 can also be suppressed.

Therefore, even if crystal growth is repeated, changes in the growth conditions due to fluctuations in the fixed cylindrical metal heater 3 or deformation of the crucible can be prevented, so oxide single crystals of the same quality can be repeatedly and stably grown. This has the effect of making it possible to

(1-4) Growth device according to a modification of the first embodiment As shown in FIG. This is the same as the growing device according to the first embodiment shown in FIG. 2 except that a portion 3c is formed.

According to the growth device according to this modification, the cylindrical metal heater 3 becomes easy to stand on its own due to the action of the ring-shaped flat portion 3c, and the work of fixing the cylindrical metal heater 3 in the oxide crucible 1 is simplified. This makes it possible to more stably fix the cylindrical metal heater 3 within the oxide crucible 1.

Incidentally, instead of the above structure in which the ring-shaped flat part 3c is formed at the lower open part of the cylindrical metal heater 3, the lower open part of the cylindrical metal heater 3 is closed to form the cylindrical metal heater 3 into a cup shape. In this case, the cylindrical metal heater 3 becomes easier to stand on its own, which has the advantage that the work of fixing the cylindrical metal heater 3 within the oxide crucible 1 becomes easier.

(2) Growing device according to second embodiment and manufacturing method of this growing device (2-1) Growing device according to second embodiment As shown in FIG. 6, the growing device according to the second embodiment has a bottom side. The growth apparatus according to the present invention (comprising an oxide crucible 1 and a cylindrical metal heater 3) is fixed on a support stand 11 and excludes the high-frequency induction coil 2, and a seed rod (crystal pulling shaft) 20 is mounted on the upper side. a heat insulating outer cylinder 13 having an opening 12 for use, a ring-shaped reflector 15 placed on the upper end 3b of the cylindrical metal heater 3, an after-heater 16 placed on this ring-shaped reflector 15, and the above-mentioned The main part is constituted by a rod-shaped seed crystal 21 attached to the lower end side of a seed rod (crystal pulling shaft) 20. In FIG. 6, reference numeral 40 indicates a ceramic container (CP crucible) that covers the outer bottom surface 1b and side walls of the oxide crucible 1.

Using this growth apparatus, an oxide single crystal can be grown in the same manner as in the growth method according to the first embodiment, and the oxide single crystal has the same quality as in the growth method in the first embodiment. It has the effect of being able to grow repeatedly and stably.

(2-2) Method of manufacturing the growth device according to the second embodiment The growth device according to the second embodiment can be manufactured, for example, as follows.

First, as shown in FIG. 4, a crystal material 10a is placed into a ceramic crucible (CP crucible) 40 built into a heat insulating outer cylinder 13, leaving an upper space 41. Incidentally, the crystal material 10a is exemplified by crystal material powder or crystal material lump.

Next, the cylindrical metal heater 3 with the ring-shaped flat part 3c formed in the lower open part is assembled into the upper space 41 of the ceramic crucible (CP crucible) 40, and the lower end 3a of the cylindrical metal heater 3 is inserted into the upper space 41 of the ceramic crucible (CP crucible) 40. It is placed on the crystal material 10a of a ceramic crucible (CP crucible) 40.

Then, as shown in FIG. 5, the crystal material 10a is put into the upper space 41 of the ceramic crucible (CP crucible) 40 in which the cylindrical metal heater 3 is incorporated, and the crystal material 10a is placed inside the cylindrical metal heater 3 and the ceramic crucible (CP crucible) The upper space 41 of the crucible 40 is filled with the crystal material 10a.

Next, as shown in FIG. 6, a ring-shaped reflector 15 is placed on the upper end 3b of the cylindrical metal heater 3, and an after-heater 16 is placed on the ring-shaped reflector 15.

Then, the cylindrical metal heater 3 is inductively heated by the high frequency induction coil 2 provided around the side wall of the ceramic crucible (CP crucible) 40, and the crystal material 10a inside the cylindrical metal heater 3 and the vicinity of the side wall of the cylindrical metal heater 3 are heated by induction. The crystalline material 10a is melted to form a raw material melt 10, and the raw material melt 10 is caused to flow between the crystalline materials 10a at a portion away from the side wall of the cylindrical metal heater 3 to form a continuous oxide layer 1c. The growth apparatus according to the second embodiment can be manufactured by forming an oxide crucible 1 having an oxide layer 1c on its inner surface and capable of storing and holding the raw material melt 10.

In addition, in the growth apparatus according to the first embodiment, as shown in FIG. 2, a ceramic container 4 that covers the outer bottom surface 1b of the oxide crucible 1 is used, and the manufacturing method using the above-described ceramic crucible (CP crucible) 40 is used. Unable to manufacture growth equipment. In such a case, a crystalline material powder or a crystalline material lump is pressure-molded into the shape of an oxide crucible as shown in FIG. After being housed in the heat insulating outer cylinder 13, it is possible to manufacture the growth apparatus according to the first embodiment by applying the above manufacturing method. At this time, it is necessary to set the wall thickness of the crucible to be pressure-molded large so that the entire wall does not melt when the cylindrical metal heater 3 is heated by induction.

(3) Crystal material constituting the oxide crucible Regarding the oxide crucible 1 having the oxide layer 1c on the inner surface and being made of a crystal material, the entire crucible does not need to be made of one crystal. It is preferable that the entire crucible is composed of a sintered body or a polycrystalline body, but a part of the crucible may be in a powder state. Note that when a part of the oxide crucible is in a powder state, it is desirable to provide the above-mentioned ceramic container for holding the powder. Incidentally, the unmelted portion of the crystal material that is away from the oxide layer 1c of the oxide crucible 1 functions similarly to the heat insulating material 108 and the heat insulating crucible stand 110 in the conventional growth apparatus shown in FIG.

The ceramic container that covers the outer bottom surface 1b of the oxide crucible 1 or the ceramic crucible that covers the outer bottom surface 1b and side walls of the oxide crucible 1 may be made of sintered materials such as alumina, zirconia, magnesia, and calcia. Solid refractories are preferred.

(4) Metal heater The shape of the metal heater mentioned above can be arbitrary as long as high-frequency induction heating is possible, but when growing high-quality crystals using the Czochralski method, the raw material melt is rotationally symmetrical with respect to the seed (seed crystal). It is desirable to have sex. For this reason, it is preferable that the metal heater also have a rotationally symmetrical shape, and it is required that the metal heater has a cylindrical shape.

In addition, the metal heater is preferably made of an unbreakable material that does not oxidize in an oxygen-containing atmosphere and is capable of high-frequency heating. Specifically, it is preferably made of platinum, iridium, rhodium alone or an alloy thereof. is desirable.

By the way, as a method for fixing the cylindrical metal heater, a rod for fixing the heater is attached to the inner wall surface of the heat insulating outer cylinder 13, a hole is provided near the upper end of the cylindrical metal heater, and the heater is inserted into this hole. A possible method is to insert a fixing rod to support it.

However, as the size of the metal heater increases for growing large crystals, the weight also increases, so the hole of the cylindrical metal heater becomes thermally deformed under the high temperature conditions during growth, making it difficult to stabilize the cylindrical metal heater. There is a concern that it will be difficult to secure the device in place.

On the other hand, in the present invention, a method is adopted in which the lower end of the cylindrical metal heater is inserted into the inner bottom surface of the oxide crucible to fix the cylindrical metal heater, and the lower end of the high frequency induction coil is inserted into the cylindrical metal heater. The lower end of the cylindrical metal heater is located above the lower end, so that the lower end of the cylindrical metal heater is difficult to be heated by induction. Therefore, even under high temperature conditions during crystal growth, it is possible to stably fix the cylindrical metal heater within the oxide crucible.

Note that the ring-shaped reflector placed on the upper end of the metal heater and the after-heater placed on the ring-shaped reflector are preferably made of the same material as the metal heater.

Hereinafter, examples of the present invention will be specifically explained by citing comparative examples (conventional examples).

[Example 1]
1. Manufacturing of the growth device according to Example 1
Lithium tantalate powder (crystalline material) 10a is placed in a ceramic crucible (CP crucible) 40 with an inner diameter of 320 mm and an inner height of 340 mm, which is built into the heat insulating outer cylinder 13 shown in FIG. 4, leaving an upper space 41. I put it in.

Next, a cylindrical metal heater 3 made of iridium with an inner diameter of 230 mm, a height of 240 mm, and a thickness of 2 mm, which has a ring-shaped flat part 3c with an opening diameter of 190 mm formed in the lower open part, is placed in the upper space of the ceramic crucible (CP crucible) 40. 41, and the lower end 3a of the cylindrical metal heater 3 was placed on the crystal material 10a of the ceramic crucible (CP crucible) 40. At this time, the lower end 3a of the iridium cylindrical metal heater 3 was adjusted to be located 30 mm below the lower end 2a of the high frequency induction coil 2.

As shown in FIG. The interior and the upper space 41 of the ceramic crucible (CP crucible) 40 were filled with lithium tantalate powder (crystalline material) 10a.

Next, as shown in FIG. 6, a ring-shaped reflector 15 was placed on the upper end 3b of the cylindrical metal heater 3, and an after-heater 16 was placed on the ring-shaped reflector 15.

Then, the cylindrical metal heater 3 is inductively heated by the high-frequency induction coil 2 provided around the side wall of the ceramic crucible (CP crucible) 40, and the lithium tantalate powder (crystal material) 10a in the cylindrical metal heater 3 and the cylindrical The lithium tantalate powder (crystalline material) 10a near the side wall of the metal heater 3 is melted to form a raw material melt 10, and the raw material is melted between the lithium tantalate powder (crystalline material) 10a at a portion away from the side wall of the cylindrical metal heater 3. Example 1 was carried out by introducing the melt 10 to form a continuous oxide layer 1c, forming an oxide crucible 1 having the oxide layer 1c on the inner surface and capable of storing and holding the raw material melt 10. Such a growing device was manufactured.

When melting the lithium tantalate powder (crystalline material) 10a to form the oxide layer 1c, in order to increase the amount of melt outside the cylindrical metal heater 3, the input power of the high-frequency induction coil 2 is adjusted as follows. It is set 10% higher than before. As a result, the raw material melt flows between the lithium tantalate powders (crystalline materials) 10a, forming a continuous oxide layer 1c.

2. Growth of lithium tantalate single crystal (1) Next, a seed rod (crystal pulling shaft) 20 with a seed crystal 21 attached to the tip is lowered and pulled up from the opening 12 (see FIG. 6) of the heat insulating outer cylinder 13. (Czochralski method), it was possible to grow a lithium tantalate single crystal with a diameter of 6 inches and a straight body length of about 150 mm.

(2) After growing the lithium tantalate single crystal, lithium tantalate powder (crystal raw material) is put into the oxide crucible 1 in which the cylindrical metal heater 3 is installed, and the high-frequency induction coil 2 The metal heater 3 was heated by induction to melt the lithium tantalate powder (crystal raw material) present inside the cylindrical metal heater 3 and the lithium tantalate powder (crystal raw material) present outside the cylindrical metal heater 3.

Next, the seed rod (crystal pulling shaft) 20 to which the seed crystal 21 is attached is lowered from the opening 12, and crystal growth is performed by the pulling method (Czochralski method). A 150 mm lithium tantalate single crystal was grown.

When the same crystal growth was repeated 40 times, it was possible to grow a lithium tantalate single crystal of the same quality, 6 inches in diameter, and about 150 mm in straight body length in 38 times.

[Comparative example (conventional example)]
Tantalum with a diameter of 6 inches and a straight body length of approximately 150 mm is produced by the pulling method (Czochralski method) using the conventional growth apparatus shown in FIG. A lithium oxide single crystal was grown.

As in Example 1, crystal growth was scheduled to be performed 40 times, but since a single crystal could not be obtained after the 24th time, the crystal growth was ended after 30 times.

Note that a single crystal was obtained 22 times out of 30 times.

The iridium crucible was deformed after the growth, and it is thought that the single crystal could not be obtained because it was significantly deformed after the 24th test.

According to the present invention, oxide single crystals of the same quality can be repeatedly and stably grown. It has availability.

1 Oxide crucible 1a Inner bottom surface 1b Outer bottom surface 2 High frequency induction coil 2a Lower end portion 3 Cylindrical metal heater 3a Lower end portion 3b Upper end portion 3c Ring-shaped flat portion 4 Ceramic container 10 Raw material melt 10a Crystal material powder 11 Support stand 12 Opening 13 Heat insulating outer cylinder 14 Heater fixing rod 15 Ring-shaped reflector 16 After heater 20 Seed rod (crystal pulling shaft)
21 Seed crystal 30 Oxide single crystal 40 Ceramic crucible 41 Upper space 100 Crucible 101 High frequency induction coil 102 Seed rod (crystal pulling axis)
103 Ring-shaped reflector 104 After heater 105 Seed crystal 106 Raw material melt 107 Insulating material 108 Insulating material 109 CP crucible (porous alumina crucible)
110 Insulating crucible stand

Claims (6)

In an apparatus for growing oxide single crystals by the pulling method,
an oxide crucible made of the crystalline material and capable of storing and holding a raw material melt;
a high frequency induction coil provided around the side wall of the oxide crucible;
a cylindrical metal heater that is incorporated into the oxide crucible, is heated by induction by the high-frequency induction coil, and whose lower end is inserted into the inner bottom surface of the oxide crucible;
An apparatus for growing an oxide single crystal, wherein the lower end of the high-frequency induction coil is located above the lower end of the cylindrical metal heater. 2. The oxide single crystal growth apparatus according to claim 1, wherein a lower open part of the cylindrical metal heater is closed or a ring-shaped flat part is formed in the lower open part. 3. The oxide single crystal growth apparatus according to claim 1, wherein the oxide single crystal is any one of a lithium niobate single crystal, a lithium tantalate single crystal, and a yttrium aluminum garnet single crystal. 4. The oxide single crystal growth apparatus according to claim 1, wherein the cylindrical metal heater is made of platinum, iridium, rhodium, or an alloy thereof. Growth of the oxide single crystal according to any one of claims 1 to 4, characterized in that the oxide crucible is provided with a ceramic container that covers the outer bottom surface of the oxide crucible, or a ceramic crucible that covers the outer bottom surface and sidewall periphery of the oxide crucible. Device. A method for growing an oxide single crystal using the growth apparatus according to claim 1,
A crystal raw material is put into an oxide crucible with a built-in cylindrical metal heater, and the cylindrical metal heater is heated by induction using a high-frequency induction coil to separate the crystal raw material existing inside the cylindrical metal heater and the cylindrical metal heater. Growth of an oxide single crystal characterized by melting the crystal raw material existing outside the cylindrical metal heater and growing the oxide single crystal by a pulling method by bringing a seed crystal into contact with the surface of the raw material melt inside a cylindrical metal heater. Method.

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