JP2023132268A - 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 an upper end part 3b held by fixing means provided above the oxide crucible and a lower end part 3a arranged to be separated upward from an inner bottom surface 1a of the oxide crucible. A lower end part 2a of the high frequency induction coil is arranged below from the lower end part 3a of the cylindrical metal heater, and prevention of the oxide crucible and cylindrical metal heater from deforming has an effect capable of repeatedly and stably an oxide single crystal having same quality and a long size.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;
It is installed in the oxide crucible and is heated by induction by the high-frequency induction coil, and the upper end is held by a fixing means provided above the oxide crucible, and the lower end is separated upward from the inner bottom surface of the oxide crucible. Equipped with a cylindrical metal heater placed in
Further, the lower end of the high frequency induction coil is located below 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 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 third invention is
In the oxide single crystal growth apparatus according to the first invention or the second invention,
The cylindrical metal heater is made of platinum, iridium, rhodium, or an alloy thereof,
The fourth invention is
In the oxide single crystal growth apparatus according to any one of the first to third 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 fifth 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 in which a cylindrical metal heater is incorporated, and the cylindrical metal heater is induction heated by a high frequency induction coil to oxidize the crystal raw material in the cylindrical metal heater and the side wall surface of the cylindrical metal heater. While melting the crystal raw material existing between the inner wall surfaces of the crucible, a seed crystal is brought into contact with the raw material melt surface in the cylindrical metal heater to grow an oxide single crystal by a pulling method, and the above-mentioned cylindrical metal The raw material melt present between the side wall surface of the heater and the inner wall surface of the oxide crucible can be supplied into the cylindrical metal heater through the gap between the lower end of the cylindrical metal heater and the inner bottom surface of the oxide crucible. It is characterized by:

According to the oxide single crystal growth apparatus according to the present invention,
Since an oxide crucible made of the same material as the raw material melt is used as a means for storing and holding the raw material melt, deformation of the crucible can be suppressed, and when growing the oxide single crystal, the raw material existing inside the cylindrical metal heater Since the cylindrical metal heater is sandwiched between the melt and the raw material melt existing outside the cylindrical metal heater, thermal deformation of the cylindrical metal heater can be suppressed, so even if crystal growth is repeated, the growth conditions will not change. This makes it possible to prevent changes.

Furthermore, since the lower end of the high-frequency induction coil is located below the lower end of the cylindrical metal heater, the lower end of the cylindrical metal heater is also inductively heated, and as a result, the side wall surface of the cylindrical metal heater and the oxide are heated. It becomes possible to replenish the raw material melt present between the inner wall surfaces of the crucible into the cylindrical metal heater through the gap between the lower end of the cylindrical metal heater and the inner bottom surface of the oxide crucible.

Therefore, it has the effect that oxide single crystals of the same quality and large length can be repeatedly and stably grown.

FIG. 1 is an explanatory diagram of the configuration of a growing device according to the present invention. FIG. 3 is an explanatory diagram showing an example of a fixing means provided above the oxide crucible. FIG. 1 is an explanatory diagram of a growing device according to a first embodiment and a growing method using this device. 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;
It is incorporated into the oxide crucible 1 and is heated by induction by the high-frequency induction coil 2, while the upper end 3b is held by fixing means (not shown) provided above the oxide crucible 1 and the lower end 3a is oxidized. A cylindrical metal heater 3 is provided upwardly away from the inner bottom surface 1a of the crucible 1, and
The lower end 2a of the high frequency induction coil 2 is located below 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, and a heater fixing rod 14 (see FIG. ), a ring-shaped reflector 15 placed on the upper end 3b of the cylindrical metal heater 3 held by the heater fixing bar 14, and an after-heater placed on the ring-shaped reflector 15. 16 and a rod-shaped seed crystal 21 attached to the lower end side of the seed rod (crystal pulling shaft) 20. In FIG. 3, 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 to form a cylindrical material. The crystal raw material in the cylindrical metal heater 3 and the crystal raw material existing between the side wall surface of the cylindrical metal heater 3 and the inner wall surface of the oxide crucible 1 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.

At this time, the raw material melt 10 existing between the side wall surface of the cylindrical metal heater 3 and the inner wall surface of the oxide crucible 1 is passed through the gap between the lower end 3a of the cylindrical metal heater and the inner bottom surface 1a of the oxide crucible 1. It becomes possible to replenish the inside of the cylindrical metal heater.

(1-3) Effects of the growth method according to the first embodiment According to the growth method according to the first embodiment, the oxide crucible 1 made of the same material as the raw material melt is applied as a storage and holding means for the raw material melt. Therefore, deformation of the crucible can be suppressed, and when growing an oxide single crystal, the raw material melt 10 existing inside the cylindrical metal heater 3 and the raw material melt 10 existing outside the cylindrical metal heater 3 form a cylindrical shape. Since the metal heater 3 is in a sandwiched state, thermal deformation of the cylindrical metal heater 3 can also be suppressed, making it possible to prevent changes in the growth conditions even if the oxide single crystal is repeatedly grown.

Furthermore, since the lower end 2a of the high-frequency induction coil 2 is located below the lower end 3a of the cylindrical metal heater 3, the lower end 3a of the cylindrical metal heater 3 is also induction heated. The raw material melt 10 existing between the side wall surface of the cylindrical metal heater 3 and the inner wall surface of the oxide crucible 1 is passed through the gap between the lower end 3a of the cylindrical metal heater 3 and the inner bottom surface 1a of the oxide crucible 1 into a cylindrical shape. It becomes possible to replenish the inside of the metal heater 3.

Therefore, the growth method according to the first embodiment has the effect of repeatedly and stably growing oxide single crystals of the same quality and large length.

(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 (comprising an oxide crucible 1 and a cylindrical metal heater 3) according to the present invention is fixed on a support stand 11 and excludes the high-frequency induction coil 2, and a seed rod (not shown) is installed on the upper side. ), a heater fixing rod 14 attached to the approximate center of the insulating outer cylinder 13 and holding the upper end 3b of the cylindrical metal heater 3; A ring-shaped reflector 15 placed on the upper end 3b of the cylindrical metal heater 3 held by a fixing bar 14, an after-heater 16 placed on this ring-shaped reflector 15, and the above-mentioned seeds (not shown). The main part consists of a rod-shaped seed crystal (not shown) attached to the lower end side of the rod (crystal pulling shaft). 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 same quality and length dimension as in the growth method according to the first embodiment can be grown. It has the effect of repeatedly and stably growing large oxide single crystals.

(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 is assembled into the upper space 41 of the ceramic crucible (CP crucible) 40, and the heater fixing rod 14 (see FIG. The upper end 3b of the cylindrical metal heater 3 is fixed by means of fixing means (see fixing means).

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 held by the heater fixing bar 14, and an after-heater 16 is placed on the ring-shaped reflector 15. place

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. The crystal material 10a near the lower end 3a is melted to form a raw material melt 10, and the raw material melt 10 is flowed between a portion of the crystal material 10a located away from the side wall of the cylindrical metal heater 3 and a portion away from the lower end 3a. A continuous oxide layer 1c is formed, and an oxide crucible 1 having the oxide layer 1c on the inner surface and capable of storing and holding the raw material melt 10 is formed to provide a growth apparatus according to the second embodiment. can be manufactured.

In addition, in the growth apparatus according to the first embodiment, as shown in FIG. 3, 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-mentioned ceramic crucible (CP crucible) 40 is used. Unable to manufacture growth equipment. In such a case, a crystal material powder or a crystal 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 for pressure molding to be 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 a material that can be subjected to high-frequency heating without being oxidized or cracked in an oxygen-containing atmosphere. Specifically, it is preferably made of platinum, iridium, rhodium alone or an alloy thereof. is desirable.

Further, as a fixing means for fixing the upper end of the metal heater, a heater fixing rod 14 (see fixing means in FIG. 2) attached to the approximate center of the heat insulating outer cylinder 13 shown in FIG. 3 is exemplified. The metal heater is fixed by passing the upper end thereof through a bar 14, and the number of heater fixing bars 14 is preferably about 2 to 6.

Further, it is preferable that the same material as the metal heater be used for the ring-shaped reflector placed on the upper end of the metal heater and the after-heater placed on the ring-shaped reflector.

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 270 mm and an inner height of 340 mm, which is incorporated into a 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 170 mm, a height of 170 mm, and a thickness of 2 mm is installed in the upper space 41 of the ceramic crucible (CP crucible) 40, and the approximately central portion of the insulating outer cylinder 13 is installed. The upper end 3b of the cylindrical metal heater 3 was fixed by a heater fixing rod 14 attached to the heater fixing rod 14.

Then, as shown in FIG. 5, lithium tantalate powder (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 installed, and the cylindrical metal heater 3 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 is placed on the upper end 3b of the cylindrical metal heater 3 held by the heater fixing bar 14, and an after-heater 16 is placed on the ring-shaped reflector 15. I placed it.

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 and the bottom end 3a is melted to form a raw material melt 10, and a part away from the side wall of the cylindrical metal heater 3 and a part away from the bottom end 3a The raw material melt 10 is made to flow between the lithium tantalate powder (crystalline material) 10a to form a continuous oxide layer 1c, which has the oxide layer 1c on the inner surface and is capable of storing and holding the raw material melt 10. A growth apparatus according to Example 1 was manufactured by forming an oxide crucible 1.

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 (not shown) with a seed crystal (not shown) attached to the tip (crystal pulling shaft ), and crystal growth was performed by the pulling method (Czochralski method), and it was possible to grow a lithium tantalate single crystal with a diameter of 4 inches and a straight body length of about 130 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 cylindrical metal heater is heated by the high frequency induction coil 2. 3 is induction heated, and the lithium tantalate powder (crystal raw material) in the cylindrical metal heater 3 and the lithium tantalate powder (crystal raw material) present between the side wall surface of the cylindrical metal heater 3 and the inner wall surface of the oxide crucible 1 are heated by induction heating. was melted.

Next, the seed rod (crystal pulling shaft) with the seed crystal attached was lowered from the opening 12 and crystal growth was performed by the pulling method (Czochralski method). A lithium tantalate single crystal was grown.

When the same crystal growth was repeated 30 times, it was possible to grow a lithium tantalate single crystal of the same quality, 4 inches in diameter, and about 130 mm in straight body length in 29 times.

[Comparative example (conventional example)]
Tantalum with a diameter of 4 inches and a straight body length of about 130 mm is produced by the pulling method (Czochralski method) using the conventional growth apparatus shown in FIG. A lithium oxide single crystal was grown.

Then, as in Example 1, when crystal growth was repeated 30 times, a lithium tantalate single crystal of the same quality was obtained 21 times, and no single crystal was obtained after the 23rd time.

This was because the crucible 100 was significantly deformed after the 23rd time.

According to the present invention, since oxide single crystals of the same quality and large length can be repeatedly and stably grown, it can be used as a growth device for oxide single crystals such as lithium tantalate single crystals used as surface acoustic wave device materials. It has industrial applicability.

1 Oxide crucible 1a Inner bottom surface 1b Outer bottom surface 2 High frequency induction coil 2a Lower end 3 Cylindrical metal heater 3a Lower end 3b Upper end 4 Ceramic container 10 Raw material melt 10a Crystal material powder 11 Support stand 12 Opening 13 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 (5)

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;
It is installed in the oxide crucible and is heated by induction by the high-frequency induction coil, and the upper end is held by a fixing means provided above the oxide crucible, and the lower end is separated upward from the inner bottom surface of the oxide crucible. Equipped with a cylindrical metal heater placed in
An apparatus for growing an oxide single crystal, wherein the lower end of the high-frequency induction coil is located below the lower end of the cylindrical metal heater. 2. The oxide single crystal growth apparatus according to claim 1, wherein the oxide single crystal is any one of lithium niobate single crystal, lithium tantalate single crystal, and yttrium aluminum garnet single crystal. 3. 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. The oxide single crystal according to any one of claims 1 to 3, further 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. Cultivation equipment. 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 in which a cylindrical metal heater is incorporated, and the cylindrical metal heater is induction heated by a high frequency induction coil to oxidize the crystal raw material in the cylindrical metal heater and the side wall surface of the cylindrical metal heater. While melting the crystal raw material existing between the inner wall surfaces of the crucible, a seed crystal is brought into contact with the raw material melt surface in the cylindrical metal heater to grow an oxide single crystal by a pulling method, and the above-mentioned cylindrical metal The raw material melt present between the side wall surface of the heater and the inner wall surface of the oxide crucible can be supplied into the cylindrical metal heater through the gap between the lower end of the cylindrical metal heater and the inner bottom surface of the oxide crucible. A method for growing an oxide single crystal characterized by:

Images