JP2022099960A - Method for manufacturing oxide single crystal, and electrode used for method for manufacturing the same - Google Patents

Abstract

To prevent such a fault that electric polarity is not the same when simultaneously subjected to annealing and polling to improve productivity.SOLUTION: A method for manufacturing an oxide single crystal, capable of subjecting an oxide single crystal grown by the Cz method to annealing and polling comprises: arranging a pair of electrodes to the oxide single crystal embedded in a crystalline oxide powder in a heat-resistant vessel; annealing the oxide single crystal at a predetermined temperature; and applying voltage to the electrodes to poll the oxide single crystal. One of the pair of electrodes has an open hole in the central part, and the seed crystal part of the oxide single crystal is installed in the open hole.SELECTED DRAWING: Figure 1

Description

The present invention relates to heat treatment and single segmentation treatment of oxide single crystals such as lithium tantalate (LiTaO ₃ : hereinafter abbreviated as LT) single crystal and lithium niobate (LiNbO ₃ : hereinafter abbreviated as LN). Concerning the processing method of performing at the same time.

Substrates obtained from single crystals are used as various materials. For example, a lithium tantalate single crystal substrate (LT single crystal substrate) obtained from a lithium tantalate (LT) single crystal, a lithium niobate single crystal substrate (LN single crystal substrate) obtained from a lithium niobate (LN) single crystal, and the like. Piezoelectric single crystal substrate (hereinafter, may be abbreviated as "single crystal substrate") is used as a material for a surface elastic wave element (SAW filter) for removing electrical signal noise used in mobile communication equipment. ..

The LT single crystal and the LN single crystal are mainly manufactured by the Czochralski method (hereinafter, may be abbreviated as the Cz method), and the Cz method heats the pit containing the raw material of the single crystal by high-frequency induction heating. The crystal raw material is brought into a melt state by heating in a furnace or a resistance heating furnace, the seed crystal in the desired orientation is brought into contact with the melt surface, and then the seed crystal is pulled up in a furnace having a temperature gradient. This is a method for growing a single crystal in the same orientation as the seed crystal. The single crystal grown by the Cz method has residual strain due to thermal stress, and in order to remove this, heat treatment (annealing) is performed under soaking heat close to the melting point. Furthermore, the single crystal grown by the Cz method is in a multi-regional state, and if it is in the multi-regional state, cracks are likely to occur during wafer processing of the single crystal, and the characteristics of nonlinear optical materials, surface acoustic wave devices, etc. affect. Therefore, it is necessary to perform a single segmentation process (polling) on the grown single crystal. In the single-segmentation process, the temperature of the single crystal is raised from room temperature to a predetermined temperature above the Curie temperature, a voltage is applied to the single crystal, the temperature is lowered to a predetermined temperature below the Curie temperature while the voltage is still applied, and then the voltage is applied. A series of treatments are performed to stop the application and cool to room temperature. After the polling process, the outer surface of the grown single crystal is ground to adjust the outer shape, and the single crystal ingot processed into a columnar shape is processed into a wafer-shaped single crystal substrate.

The annealing and polling described above are performed individually, but in the case of a variety having a Curie temperature close to the melting point, for example, an LN single crystal, the annealing and polling are performed at the same time, and the cooling time after annealing and the upper and lower sides of the single crystal are performed. A method of shortening the cutting work of the electrode forming portion for cutting the polling and improving the productivity is being studied. A method of performing annealing and polling at the same time (collectively) is described in Patent Document 1 and Patent Document 2 below.

Japanese Unexamined Patent Publication No. 58-2083 Japanese Unexamined Patent Publication No. 2007-1775

By the way, in the single crystal grown by the Cz method, the seed crystal in a desired orientation is brought into contact with the melt surface, and then the seed crystal is pulled up while rotating to grow the single crystal. The single crystal grown in this way has a seed crystal on the upper side. The length of the seed crystal is about 5 to 10 cm. Conventionally, a seed crystal is annealed, cooled, cut, and then polled.

However, when annealing and polling are performed at the same time, the state of the single crystal before annealing has residual strain due to thermal stress during growth, and there is a high probability that the single crystal will crack when the seed crystal is cut. It is difficult to cut into. Therefore, when annealing and polling are performed at the same time, it is necessary to perform the annealing and polling in a state where the single crystal has a seed crystal.

In Patent Document 1, the seed crystal portion (seed crystal portion) on the upper side of the single crystal is covered with a tubular platinum electrode, and the inside of this electrode is a conductive material such as Ag paste made of a thermosetting resin containing silver powder. It is filled with. On the lower side of the single crystal, the single crystal is placed on the platinum electrode via a powder of the same type as the single crystal. In this method, the upper electrode and the lower electrode have different shapes, and in particular, the upper electrode is smaller than the crystal shape, so that there is a possibility that voltage cannot be applied to the entire crystal and proper processing cannot be performed. In addition, it is necessary to fill the upper electrode with Ag paste or the like, which causes problems such as poor workability.

In polling, there is also a method in which a single crystal is placed in a heat-resistant container and platinum electrodes are arranged in pairs above and below the single crystal and embedded in crystal powder. In the case of this method, when embedding a single crystal, since there is a seed crystal on the upper side of the single crystal, it is necessary to arrange it on the upper side of the upper end of the seed crystal so as not to come into contact with the seed crystal. Therefore, the vertical distance between the electrode and the single crystal cannot be made the same, and as a result, polling cannot be performed properly, and the electrical polarities of the single crystal may not be uniform. If the electrical polarities are not aligned, you will need to poll again. When polling is performed again, the crack rate of the single crystal becomes high. As described above, it was found that in the conventional method, when annealing and polling are performed at the same time, the electrical polarities of the single crystal may not be the same, which causes a decrease in productivity such as polling again. ..

Therefore, the present invention has been made by paying attention to the above-mentioned problems, and the problem thereof is to prevent problems such as the electrical polarities not being aligned in the process of performing annealing and polling at the same time. The purpose is to improve productivity.

According to the aspect of the present invention, it is a method for producing an oxide single crystal in which an oxide single crystal grown by the Cz method is annealed and polled, and the oxide single crystal is embedded in an oxide crystal powder in a heat-resistant container. On the other hand, a pair of electrodes is arranged, annealed at a predetermined temperature, and then a voltage is applied to the electrodes to poll the oxide single crystal, and one of the pair of electrodes has a through hole in the center. Provided is a method for producing an oxide single crystal, wherein the seed crystal portion of the oxide single crystal is installed in the through hole.

Further, the pair of electrodes may be arranged substantially evenly above and below the oxide single crystal. Further, the hole diameter of the through hole of the electrode may be 5 mm or more and 20 mm or less larger than the size of the seed crystal. Further, the seed crystal portion may be covered with an insulating sheet before the seed crystal portion of the oxide single crystal is inserted into the through hole of the electrode.

Further, according to the aspect of the present invention, the electrode used in the above-mentioned method for producing an oxide single crystal, the electrode has a through hole in the central portion, and the seed crystal portion of the oxide single crystal is contained in the through hole. Electrodes are provided, which can be installed.

According to the aspect of the present invention, in the process of performing annealing and polling at the same time, it is intended to prevent problems such as inconsistent electrical polarities and improve productivity.

It is a figure which shows an example of the manufacturing method of the oxide single crystal which concerns on embodiment. It is a flowchart of an example of the manufacturing method of the oxide single crystal which concerns on embodiment. It is a figure which shows an example of the manufacturing method of the oxide single crystal which concerns on embodiment. It is a figure which shows an example of the manufacturing method of the oxide single crystal which concerns on embodiment. It is a figure which shows an example of the manufacturing method of the oxide single crystal which concerns on embodiment. It is a figure which shows an example of the manufacturing method of the oxide single crystal which concerns on embodiment. It is a figure which shows an example of the manufacturing method of the oxide single crystal which concerns on embodiment.

[Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, a part or the whole is schematically described as appropriate, and the scale is changed and described. Further, in the following description, the description of "A to B" means "A or more and B or less" or "B or more and A or less".

As described above, the single crystal grown by the Cz method or the like has residual strain due to thermal stress, and in order to remove this, heat treatment (annealing) is performed under a soaking temperature close to the melting point. Furthermore, the single crystal grown by the Cz method is in a multi-regional state, and if it is in the multi-regional state, cracks are likely to occur during wafer processing of the single crystal, and the characteristics of nonlinear optical materials, surface acoustic wave devices, etc. affect. Therefore, it is necessary to perform a single segmentation process (polling) on the grown single crystal. In the single-segmentation process, the temperature of the single crystal is raised from room temperature to a predetermined temperature above the Curie temperature, a voltage is applied to the single crystal, the temperature is lowered to a predetermined temperature below the Curie temperature while the voltage is still applied, and then the voltage is applied. A series of treatments are performed to stop the application and cool to room temperature.

In the above description, annealing and polling are performed individually, but in the case of a variety having a Curie temperature close to the melting point, for example, an LN single crystal, annealing and polling can be performed at the same time. However, in the state before annealing, there is residual strain due to thermal stress during growth, and the probability that a single crystal will crack when cut is high, so it is difficult to cut the seed crystal portion. Therefore, when annealing and polling are performed at the same time, it is necessary to perform the annealing and polling in a state where the single crystal has a seed crystal. However, the conventional method has the above-mentioned problems.

A method for producing an oxide single crystal (hereinafter, also referred to as “simultaneous treatment method”) in which annealing and polling of the present embodiment are performed at the same time will be described with reference to the drawings. FIG. 1 is a diagram showing an example of a method for producing an oxide single crystal according to the present embodiment.

The method for producing an oxide single crystal (simultaneous treatment method) of the present embodiment is an oxide single crystal obtained by annealing and polling an oxide single crystal C (sometimes abbreviated as "single crystal") grown by the Cz method. The pair of electrodes E1 and E2 are arranged with respect to the oxide single crystal C embedded in the oxide crystal powder P in the heat-resistant container 1, annealed at a predetermined temperature, and then the electrode E1. , E2 is provided with a voltage applied to the oxide single crystal C to poll the oxide single crystal C, and one of the pair of electrodes E1 and E2 E2 has a through hole H in the central portion and the oxide single crystal in the through hole H. The seed crystal part SC of C is installed. The simultaneous processing method of the present embodiment solves the above-mentioned problem.

Hereinafter, the simultaneous processing method will be specifically described. The simultaneous processing method can be carried out using a heat-resistant container used in conventional polling. The heat-resistant container 1 used in this simultaneous treatment method is a container having a bottom portion 2 and a side wall portion 3, as shown in FIG. 1, for example. Further, the heat-resistant container 1 may be provided with a lid portion. The configuration of the lid portion is not particularly limited and is arbitrary. The shape of the heat-resistant container 1 is not particularly limited, but may be a bottomed cylinder or a bottomed square (bottomed square cylinder). The material of each part of the heat-resistant container 1 may be any material that can withstand the polling processing temperature, and for example, alumina or the like can be used as in the conventional heat-resistant container. Crystal powder P is housed in the heat-resistant container 1. As the crystal powder P, the same one as the conventional method can be used. For example, the crystal powder P preferably has a composition similar to that of the single crystal C, and substantially the same composition is preferable in that the influence on the composition of the single crystal C is small. Further, the crystal powder P is preferably a single crystal powder in that the above influence is low. The single crystal C and the pair of electrodes E1 and E2 are embedded in the crystal powder P housed in the heat-resistant container 1.

The electrodes used in this simultaneous processing method are characteristic. The electrodes E1 and E2 are arranged so as to be paired with the single crystal C interposed therebetween. The lower electrode E1 is arranged on the lower side of the single crystal, and the upper electrode E2 is arranged on the upper side of the single crystal. For example, in the present embodiment, in the pair of electrodes E1 and E2, the single crystal C is arranged so as to sandwich the single crystal C from the vertical direction (vertical direction) of the heat-resistant container 1 as illustrated in FIG. In this simultaneous processing method, the upper electrode E2 arranged on the upper side of the single crystal C has a through hole H in the central portion (in a plan view) viewed from above the electrode E2. The through hole H is formed so that the seed crystal portion SC of the single crystal C, which will be described later, can be installed, and is a hole into which the seed crystal portion SC is inserted. The size (hole diameter) of the through hole H is set to be 5 mm to 20 mm larger than the size of the seed crystal in order to prevent the seed crystal SC from coming into contact with the through hole H when the electrode E2 is installed in the heat-resistant container 1. Is preferable. If it is less than 5 mm, there is a high possibility that it will come into contact with the seed crystal portion SC when the electrode E2 is installed. If it exceeds 20 mm, the voltage may not be applied to the central portion of the single crystal C. The shape of the through hole H is not particularly limited, and for example, the shape of the cross section orthogonal to the hole axis of the through hole H may be circular or rectangular. The size of the seed crystal portion SC is the diameter in the case of a circle and the diagonal length in the case of a square. The single crystal C used in this simultaneous treatment method is not particularly limited as long as it is produced by the Cz method and has a seed crystal portion SC, and is arbitrary. For example, the component (composition), size, and shape of the single crystal C are arbitrary.

Further, when the seed crystal portion SC of the single crystal C is inserted into the through hole H of the upper electrode E2, the seed crystal portion SC of the single crystal C is formed with an insulating sheet (not shown) before the insertion so that they do not come into contact with each other. You may cover it. When covering the seed crystal portion SC with the insulating sheet, the entire seed crystal portion SC may be covered, or the side portion of the seed crystal portion SC may be covered.

Since the grown single crystal C before annealing has high pyroelectricity, when it comes into contact with a metal such as an electrode, it causes an electric discharge and easily cracks. Therefore, as described above, by protecting the seed crystal portion SC with the insulating sheet, contact with the electrode can be prevented and the generation of cracks can be suppressed.

The insulating sheet (not shown) is not particularly limited as long as it does not have electrical conductivity, but may be, for example, a heat-resistant resin material such as a Teflon sheet (Teflon is a registered trademark). Since the single crystal C grown as described above has high pyroelectricity, when the temperature of the single crystal C is lowered to 50 ° C. or lower, the crystal surface is charged due to the temperature difference between the inside and outside of the crystal due to the temperature change. The single crystal C may be cracked due to a discharge due to the atmosphere of the crystal surface or the like, and the work is performed in a state where the single crystal before annealing is kept at a temperature of 50 ° or more. Therefore, the insulating sheet preferably has a heat resistance of about 100 ° C. The thickness of the insulating sheet is preferably 0.1 mm to 0.5 mm. If the thickness of the insulating sheet is thick, it becomes difficult to wind it around the seed crystal portion SC. The insulating sheet is removed when the electrodes E1 and E2 are embedded in the crystal powder P and the electrodes E1 and E2 are fixed.

A predetermined voltage is set between the single crystal C and the pair of electrodes E1 and E2. It is desirable that the distances L1 and L2 (shortest distance) between the single crystal C and the pair of electrodes E1 and E2 are substantially uniform. The distances L1 and L2 (shortest distance) between the single crystal C and the pair of electrodes E1 and E2 are preferably 15 mm to 50 mm, although it depends on the diameter of the crystal. Here, the shortest distance L1 and L2 between the electrodes E1 and E2 and the single crystal C is the shortest distance between the single crystal C excluding the seed crystal portion SC and the electrode E1 or the electrode E2. In this embodiment, since the seed crystal portion SC is inserted into the through hole H of the upper electrode E2, the position of the upper electrode E2 can be aligned so that the shortest distance L1 between the lower side of the single crystal C and the electrode E1 is obtained. Therefore, the electrodes E1 and E2 can be easily installed so that the shortest distances L1 and L2 between the electrodes E1 and E2 and the single crystal C are substantially uniform. As a result, the vertical distances L1 and L2 between the electrodes E1 and E2 and the single crystal C can be made the same, so that polling cannot be performed properly and it is possible to prevent the single crystal C from having the same electrical polarity. be able to. In addition, almost uniform is a range including a difference of ± 5 mm. For example, when the distances L1 and L2 (shortest distance) between the single crystal C and the pair of electrodes E1 and E2 are set to 20 mm, the shortest distances L1 and L2 are almost equal if they are in the range of 15 mm to 25 mm.

Further, it is preferable that the single crystal C is evenly installed vertically and horizontally in the crystal powder P filled in the heat-resistant container 1 so that the single crystal C treated in the heat-resistant container 1 has a uniform temperature.

The size of the electrodes E1 and E2 is preferably set according to the size of the single crystal C. The size of the electrodes E1 and E2 is preferably larger than that of the single crystal C projected from an arbitrary direction. The single crystal C is preferably arranged in the region R1 (see FIG. 1) within the pair of electrodes E1 and E2. As a result, a voltage can be applied to the entire single crystal C. The region R1 between the pair of electrodes E1 and E2 is a region between the electrodes E1 and E2 as shown by the two-dot chain line in FIG.

Next, an example of this simultaneous processing method will be described with the case of a single crystal. FIG. 2 is a flowchart of an example of this simultaneous processing method. 3 to 7 are diagrams showing an example of the present simultaneous processing method.

In this simultaneous treatment method, the single crystal crystal powder P, the single crystal C, and the electrodes E1 and E2 are set in the heat-resistant container 1. The electrodes E1 and E2 used are as described above.

(Step S1)
In this simultaneous processing method, first, the electrode E1 is arranged. For example, the lower electrode E1 is installed (set) on the bottom 2 of a heat-resistant container 1 made of alumina or the like (steps S1 and 3 in FIG. 2).

(Step S2)
Subsequently, the crystal powder P is placed in the heat-resistant container 1 (steps S2 and 4 in FIG. 2). In step S2, a predetermined amount of crystalline crystal powder P is added. The crystal powder P is installed so that the minimum distance L1 between the single crystal C and the electrode E1 is a predetermined distance. At this time, preferably, the crystal powder P is installed so that the minimum distance L1 between the electrode E1 and the single crystal C is about 20 mm (15 to 25 mm). As for the crystal powder P installed in the heat-resistant container 1, since the grown single crystal is discharged in a conical shape on the lower side of the single crystal, it is simply formed into a mortar shape so that the central portion of the crystal powder P is recessed. It is preferable because the crystal C is stable and easy to arrange.

(Steps S3, S4)
Subsequently, the single crystal C is placed on the crystal powder P (steps S3 and 5 in FIG. 2). In the single crystal C, it is preferable to protect the seed crystal portion SC with the insulating sheet by covering the seed crystal portion SC with the above-mentioned insulating sheet (not shown) before installation (step S4 in FIG. 2). .. The single crystal C is installed so that the seed crystal portion SC is on the upper side.

(Step S5)
Subsequently, the crystal powder P is filled, and the entire single crystal C is embedded in the crystal powder P (steps S5 and 6 in FIG. 2). For example, the crystal powder P is filled so as to cover the surface of the single crystal C, and the entire single crystal C is embedded.

(Step S6)
Subsequently, the upper electrode E2 is placed on the crystal powder P in which the single crystal C is embedded (steps S6 and 7 in FIG. 2). The upper electrode E2 has a through hole H, and the seed crystal SC covered with the insulating sheet of the single crystal C is inserted into the through hole H to install the upper electrode E2. At this time, the distance L2 between the upper electrode E2 and the single crystal C excluding the seed crystal portion SC of the single crystal C is set to be equal to the minimum distance L1 between the electrode E1 and the single crystal C. As described above, according to this simultaneous processing method, the vertical distances L1 and L2 between the electrodes E1 and E2 and the single crystal C can be made the same, so that polling cannot be performed properly and the electrical polarity of the single crystal cannot be obtained. It can be suppressed that the polling is not aligned.

(Step S7)
Subsequently, the crystal powder P is refilled in an appropriate amount to cover the electrode E2, and the upper end portion of the seed crystal portion SC is embedded in the crystal powder P (step S7 in FIG. 2, FIG. 1). The upper electrode E2 is embedded in the crystal powder P, and when the upper electrode E2 is fixed, the insulating sheet is removed.

(Step S8)
Subsequently, annealing and polling are simultaneously (collectively) performed on the single crystal C embedded in the crystal powder P as in step S7 (step S8 in FIG. 2). In step S8, the single crystal C embedded in the crystal powder P is annealed and polled at the same time (collectively) without performing other treatments such as movement in the same heat-resistant container 1. In step S8, the single crystal C embedded in the crystal powder P is annealed at a predetermined temperature, and then polled. A voltage is applied at a predetermined temperature to be polled. Known conditions can be used for the temperature and voltage at the time of annealing and polling.

As described above, this simultaneous treatment method is a method for producing an oxide single crystal in which the single crystal C grown by the Cz method is annealed and polled, and the single crystal is embedded in the crystal powder P in the heat-resistant container 1. A pair of electrodes E1 and E2 are arranged with respect to C, annealed at a predetermined temperature, and then a voltage is applied to the electrodes E1 and E2 to poll the single crystal C, and the pair of electrodes E1 and E2 are provided. One of the electrodes E2 has a through hole H in the central portion, and the seed crystal portion SC of the single crystal C is installed in the through hole H. In this simultaneous processing method, the configurations other than the above are arbitrary configurations. According to this simultaneous processing method, in the processing of performing annealing and polling at the same time, it is possible to prevent problems such as inconsistent electrical polarities and improve productivity. Further, since this simultaneous treatment method is the same as the conventional method except that the through hole H is formed in the electrode E2, it can be easily carried out.

(electrode)
Next, the electrodes according to the embodiment will be described. The electrode according to the embodiment is the above-mentioned electrode E2 used in the above-mentioned simultaneous processing method. As described above, the electrode E2 has a through hole H in the central portion, and the seed crystal portion SC of the single crystal C can be installed in the through hole H. According to the electrode of the present embodiment, since the above-mentioned simultaneous processing method can be performed, it is possible to prevent problems such as the electrical polarities not being aligned in the processing of performing annealing and polling at the same time, and improve productivity.

Hereinafter, the present invention will be specifically described with reference to examples of the present invention, but the present invention is not limited to these examples.

[Example 1]
In Example 1, the LN single crystal was annealed and polled using the simultaneous treatment method and electrodes according to the present embodiment described above. In Example 1, a 128 ° RY LN single crystal (Curie point: 1140 ° C.) having a congluent composition and a diameter of φ160 mm (6.3 inches) and a total length of 100 mm was used. The seed crystal had a size of φ10 mm and a length of 70 mm.

First, as shown in FIG. 1, a cylindrical heat-resistant container having a bottom was prepared. The heat-resistant container was made of alumina having an inner diameter of φ300 mm, a height of 300 mm, and a thickness of 20 mm. Next, an electrode (lower electrode) having a diameter of φ200 mm and a thickness of 0.3 mm was installed on the bottom (bottom surface). Next, the single crystal powder P obtained by crushing the LN crystal was laid on the bottom surface of the heat-resistant container. Further, the single crystal powder was formed into a mortar shape having a concave shape in the vicinity of the central portion when viewed from above.

An insulating sheet having a thickness of 0.1 mm was wound around the seed crystal portion of the LN single crystal. This LN single crystal was placed in a heat-resistant container. The minimum distance between the electrode and the single crystal was set to 20 mm. The inside of the heat-resistant container was filled with a single crystal powder around the single crystal. An electrode (upper electrode) having a through hole with a diameter of φ200 mm, a thickness of 0.3 mm, and a through hole of φ25 mm in the center is placed 20 mm from the upper surface of the single crystal excluding the seed crystal, and the electrode penetrates the seed crystal part covered with an insulating sheet. It was inserted into the hole and placed. The single crystal powder was filled on the upper electrode, and the insulating sheet was removed after the upper electrode was fixed with the single crystal powder. Then, the single crystal powder was filled up to a position 10 mm from the end of the seed crystal.

After arranging the heat-resistant container containing the single crystal on the hearth plate of the elevating electric furnace as described above, the platinum wire of the electrode facing the lower side of the single crystal is used as the positive electrode, and the electrode facing the upper side of the single crystal is used. The platinum wire was connected to a DC power supply as a negative electrode. The temperature of the electric furnace was raised to 1150 ° C., held for 30 hours until the single crystal became stable, and 28 hours after reaching 1150 ° C., a 15 V voltage was applied between the electrodes, and the temperature was lowered after about 90 minutes. , Annealing, and polling were performed at the same time.

After annealing and polling, the heat-resistant container was taken out from the electric furnace. Then, the single crystal was taken out from the heat-resistant container.

When the LN single crystal after the annealing and polling treatment was examined, no cracks were generated, and when the polarization state of the LN single crystal was evaluated, there was no polarization in the opposite direction, and the single domain was satisfactorily divided. When the above was repeated 50 times, there was no problem that the electrical polarities were not aligned. The evaluation of the single segmentation of the crystal was performed based on the obtained waveform using an oscilloscope and a probe terminal. If no waveform appears, it is considered that it is not single-segmented.

[Comparative Example 1]
In Comparative Example 1, the seed crystal was left attached to the single crystal, and an upper electrode having no through hole was provided at a distance of 20 mm above the end of the seed crystal of the single crystal. Other conditions were the same as in Example 1, and annealing and polling processing were performed. As a result of evaluation of the single segmentation of the crystal after the treatment, a problem that the electrical polarities were not aligned occurred.

From the results of the above Examples and Comparative Examples, it was confirmed that the method for producing an oxide single crystal of the present embodiment has a remarkable effect of preventing problems such as the electrical polarities not being aligned in polling of the oxide single crystal. Will be done.

The technical scope of the present invention is not limited to the embodiments described in the above-described embodiments. One or more of the requirements described in the above embodiments and the like may be omitted. Further, the requirements described in the above-described embodiments and the like can be appropriately combined. In addition, to the extent permitted by law, the disclosure of all documents cited in the above-mentioned embodiments, etc. shall be incorporated as part of the description in the main text.

1 ... Heat-resistant container 2 ... Bottom 3 ... Side wall C ... Oxide single crystal (single crystal)
SC ... Seed crystal P ... Oxide crystal powder (crystal powder)
E1, E2 ... Electrode H ... Through hole

Claims (5)

It is a method for producing an oxide single crystal in which an oxide single crystal grown by the Cz method is annealed and polled.
A pair of electrodes are placed on the oxide single crystal embedded in the oxide crystal powder in a heat-resistant container, annealed at a predetermined temperature, and then a voltage is applied to the electrodes to poll the oxide single crystal. In preparation for that
A method for producing an oxide single crystal, wherein one of the pair of electrodes has a through hole in the center and a seed crystal portion of the oxide single crystal is installed in the through hole. The method for producing an oxide single crystal according to claim 1, wherein the pair of electrodes are arranged substantially evenly above and below the oxide single crystal. The method for producing an oxide single crystal according to claim 1 or 2, wherein the pore diameter of the through hole of the electrode is 5 mm or more and 20 mm or less larger than the size of the seed crystal. The oxide according to any one of claims 1 to 3, wherein the seed crystal portion of the oxide single crystal is covered with an insulating sheet before the seed crystal portion is inserted into the through hole of the electrode. A method for producing a single crystal. An electrode used in the method for producing an oxide single crystal according to claim 1.
The electrode has a through hole in the center and has a through hole.
An electrode in which the seed crystal portion of the oxide single crystal can be installed in the through hole.

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