JPH03215386A - Production of oxide single crystal - Google Patents

Abstract

PURPOSE:To effectively control shape of a solid-liquid interface in melt in pulling up of crystal to improve quality of a single crystal by growing an oxide single crystal from melt in a crucible with making a ratio of a crystalline diameter of pulledup single crystal to an inner diameter of the crucible in a specific range. CONSTITUTION:An oxide single crystal is grown with making a ratio of a crystalline diameter of pulled-up single crystal to an inner diameter of a crucible to 0.65-0.75 in growing the oxide single crystal from melt in the crucible by a pulling-up method. Said method is utilizable to all of various methods in the pulling-up method, thus an oxide single crystal such as LiNbO3 or LiTaO3 is advantageously obtained. For <=0.65 said ratio of a crystalline diameter to an inner diameter of the crucible, a shape ratio (a/L) at a solid-liquid interface of a single crystal 8 becomes smaller than -0.05 and a shape of the interface becomes concave (upwardly protruding), thus crystallinity is decreased. On the other hand, for >=0.75 of said ratio, crystallinity is also decreased, while the shape of the interface is downwardly protruding, thus improving of quality of the resultant single crystal 8 is difficult.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to L iNbo. , LiTaos, etc., and particularly relates to a method of manufacturing such an oxide single crystal by a pulling method.

(11th Background Art) Various methods have been known for producing this type of oxide single crystal, but one of them, the pulling method (Czochralski method), From the liquid
This method involves growing and pulling the desired oxide single crystal, and is in practical use as a method for producing large-diameter, high-quality oxide single crystals.

By the way, in order to grow a high-quality single crystal using such a pulling method, it is important to control the solid-liquid interface of the single crystal. By moving the work coil, slowing down the relative rotation speed and pulling speed of Lupo and the single crystal, etc.
Single crystals are being grown. This is because it is said that in order to grow a high-quality single crystal, it is desirable that the solid-liquid interface shape be flat. If the shape of the solid-liquid interface is not flat, macroscopic defects such as cracks and bubbles will appear in the pulled and grown single crystal.

However, it is difficult to control the solid-liquid interface of the single crystal in the pulling method only by changing the conditions that have been proposed in the past, and therefore, there is a problem that a high-quality single crystal cannot be obtained.

(Problem to be solved) The present invention has been made against the background of the above, and its object is to solve the problem of the shape of the melt-solid-liquid interface during pulling of an oxide single crystal in the pulling method. The objective is to provide a method that can effectively control the

(Solution Means) In order to solve this problem, the present invention aims to reduce the ratio of the crystal diameter of the pulled single crystal to the inner diameter of the crucible to 0 when growing an oxide single crystal from the melt in the Lupo by the pulling method. .65
The gist of the above is a method for producing an oxide single crystal, which is characterized in that the growth is carried out at a value of 0.75 or less.

(Specific structure/effect) In short, it has been known for a long time that the shape of the solid-liquid interface depends on the rotation speed of the crystal when pulling an oxide single crystal using the pulling method, but the present inventors have conducted various studies. As a result, it was found that the shape of the solid-liquid interface depends on the ratio (crystal diameter/crucible diameter) between the pulled crystal and the inner diameter (diameter) of the melting tube used for pulling. , was completed based on such knowledge.

That is, an example of a pulling method is schematically shown in FIG. 1, and in such a pulling method, the crystal diameter (L)/
As the crucible diameter (φ) ratio increases, the solid-liquid interface shape of the crystal becomes convex downward, and in the present invention, the L/φ ratio is 0.65 to 0.75. In this way, the solid-liquid interface shape becomes flat or slightly convex, improving crystallinity, thereby suppressing the occurrence of crystal defects, and increasing the yield. This improved the quality of the single crystal produced.

Note that the present invention can be applied to any of various methods known as a pulling method, and thereby LiNbOz. This advantageously provides oxide single crystals such as LiTao3.

For example, in the pulling method schematically shown in FIG. 1, a high frequency induction heating furnace is used, and a crucible 4 is heated by a work coil (induction coil) 2 of the furnace. The crucible 4 contains a melt 6 of an oxide that provides the desired single crystal, and this melt 6
As is well known, seeding is performed using a seed crystal, and while the crystal is grown from the seed crystal, the grown single crystal 8 is gradually pulled up from the melt 6. In addition, when growing such a crystal 8, as in the conventional case, the single crystal 8 is rotated around its axis, the crucible 4 is rotated, and the relative relationship between the single crystal 8 and the crucible 4 is changed. A rotation is performed.

Further, the crystal diameter (L) of the single crystal 8 is controlled using a known automatic crystal diameter control device (ADC) or the like. This automatic crystal diameter control device (ADC) measures the crystal diameter (L) from the weight measurement of the grown single crystal 8, and controls the amount of heating by the work coil 2, etc.
This is to ensure that the single crystal 8 to be grown has a desired crystal diameter (L).

In the present invention, in such a pulling method, the crystal diameter (L)
The single crystal 8 is grown so that the ratio of crucible diameter (φ) is 0.65 to 0.75.
As shown in the figure, a single crystal 8 having an outer shape with a flat or slightly downwardly convex tail portion is obtained. In addition, when L/φ is less than 0.65, the shape ratio (a/L) of the solid-liquid interface becomes a value smaller than -0.05, and the interface shape becomes concave (upward convex). On the other hand, when L/φ exceeds 0.75, although the interface shape is downward convex, the crystallinity deteriorates and the quality of the obtained single crystal 8 is improved. It becomes difficult to discipline.

(Example) Below, typical examples of the present invention will be shown to clarify the present invention more specifically. However, the present invention is not limited in any way by the description of such examples. Needless to say, it is not something that can be accepted.

First, a LiNbOs sintered body was placed in a 120 mφ platinum crucible, heated to 1300°C by high frequency induction heating to melt it, and after seeding, a crystal shoulder was grown and the crystal was grown at a pulling rate of 3/hr. Under the conditions of rotation speed: 8 rpm and crucible rotation speed: Orpm, the crystal diameter was set as shown in Table 1 below, and the automatic crystal diameter control device (ADC) was used.
A LiNbO3 single crystal was grown under control. After pulling, the obtained single crystal was cut and its interface shape (a/L) was observed, and the results are shown in Table 1 below. Also, using a 150 φ crucible, LiNbO. The results of growing single crystals are also shown in the first section below.
It is also shown in the table.

Furthermore, the results of Table 1 are shown in FIG.

From the results shown in Table 1 and Figure 3, L/φ is set to 0.6.
It has been found that when the value is 5 or more, the solid-liquid interface becomes flat or downwardly convex.

In addition, when crystal defects were measured for various LiNbOs single crystals obtained in this way, it was found that when the crystal diameter/crucible diameter (L/φ) was 0.65 to 0.75, the solid-liquid interface shape ( a/L) is -0.05 to 0.1
0, indicating that good crystals with few crystal defects can be obtained. In addition, the quality of crystal defects is 0.5 from each single crystal.
The judgment was made based on a photograph taken by cutting out a wafer with a thickness of about 100 mm and measuring it using an X-ray tobograph. That is, the inside of the wafer is divided into squares of 7 squares, the presence or absence of defects in the squares is measured, and the ratio of the squares with defects to all the measured squares is calculated, and the ratio is set from 0 to 1.
Those with a defect rate of 0% were evaluated as good: O, those with a defect rate of 10 to 20% were evaluated as moderate: Δ, and those with a defect ratio of 20% or more were evaluated as poor: ×. The results are also shown in Table 1 below. No. 1 O: Defect ratio 0-10% Δ: 10-20% In the manufacturing process, the shape of the solid-liquid interface can be controlled arbitrarily, and high-quality single crystals can be advantageously obtained by growing with an effective solid-liquid interface shape. .

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing an example of a single crystal pulling device, FIG. 2 is an outline diagram showing an example of a single crystal produced by such a pulling device, and FIG. ,
Various crystal diameters/Luppo diameter (L/φ
) is a graph showing the results of the solid-liquid interface shape (a/L). 2: Work coil 4: Crucible 6: Melt 8: Single crystal

Claims (2)

[Claims] (1) When growing an oxide single crystal from the melt in a crucible using the pulling method, the ratio of the crystal diameter of the pulled single crystal to the crucible inner diameter is 0.65 or more and 0.75 or less. Characteristic method for producing oxide single crystals. (2) The manufacturing method according to claim (1), wherein the oxide single crystal is LiNbO_3.