KR20120120740A - Apparatus for growing sapphire single crystal - Google Patents

Abstract

PURPOSE: An apparatus for growing a sapphire single crystal is provided to suppress bubbles in the sapphire single crystal by remelting the lower section of the sapphire single crystal by a forced convection. CONSTITUTION: A crucible(120) receives aluminum oxide melt(130) and is installed in an insulation container(110). A convection blocking layer(180) is connected to the sidewall of the insulation container. An inner space(190) for receiving a sapphire single crystal(170) is formed in the convection blocking layer. The lower side of the convection blocking layer is located in the aluminum oxide melt.

Description

Sapphire single crystal growth device {APPARATUS FOR GROWING SAPPHIRE SINGLE CRYSTAL}

The present invention relates to an apparatus for growing sapphire single crystals. More specifically, the present invention relates to a sapphire single crystal growth apparatus in which bubble defects do not occur in the grown sapphire single crystal.

Sapphire is a single crystal of aluminum oxide (Al ₂ O ₃ ) having a hexagonal crystal structure. Sapphire single crystal is used as a substrate in the manufacture of light emitting diodes (LEDs). Examples of the sapphire single crystal manufacturing method include Czochralski method (hereinafter referred to as CZ method), Bernoulli method, Kiroprose method, EFG method, and HEM method. Among them, the CZ method is very effective because the single crystal can be enlarged, the temperature gradient can be easily adjusted to produce a high quality single crystal, and the waste of raw materials can be prevented during the production of the C surface substrate. In addition, in recent years, the diameter of the substrate is increasing in order to increase the productivity and reduce the manufacturing cost during LED manufacturing, and in this trend, sapphire crystal growth using the Cz method has many advantages.

1 shows a conventional sapphire single crystal growth apparatus using the Cz method.

The crucible 12 located inside the heat insulating material container 11 is filled with aluminum oxide, and the crucible 12 is heated using the high frequency coil 14. The aluminum oxide is melted by the heat of the crucible 12 to form the molten metal 13. The seed crystal 16 is connected to the lower end of the impression rod 15, and the seed crystal 16 is brought into contact with the molten metal 13, and then gradually pulled up while rotating to grow the sapphire single crystal 17. As shown in FIG.

The crucible 12 is heated by the high frequency coil 14 and is in a high temperature state. Therefore, the molten metal located on the sidewall side of the crucible 12 receives heat to lower the density and rises upward, and descends downward from the center of the crucible 12. Thus, a convection flow such as an arrow shown in FIG. 1 is formed (hereinafter, the convection of the flow is referred to as "natural convection"). By this natural convection, the sapphire single crystal 17 grows in a convex form expanded in the molten metal 13 direction. Bubble defects tend to occur in the sapphire single crystal 17 growing in such a form.

If bubble defects exist in the single crystal, cracking is liable to occur during processing, and when used as a substrate material or an optical material, a problem of insufficiently exhibiting the properties of sapphire occurs. Bubble defects occur due to the anisotropic properties of the sapphire single crystal. In other words, the growth rate of the crystal is different depending on the growth direction, and bubble defects occur in the slow growth portion.

In order to prevent such bubble defects, Japanese Laid-Open Patent Publication No. 2008-207992 discloses a technique of increasing the rotation speed of a single crystal to 40 RPM or more to form a single crystal lower end surface in parallel with the surface of the molten metal. This increases the rotational speed of the single crystal to increase the forced convection, and raises the hot melt at the bottom of the crucible to the top to form a cross section of the lower portion of the single crystal in parallel. However, such a structure is effective in sapphire single crystals having a diameter of 100 mm or less, but problems arise when growing sapphire single crystals having a diameter of 100 mm or more. This is because when the sapphire single crystal having a diameter of 100 mm or more is rotated to 40 RPM or more, the convection in the crucible changes very irregularly because the lower cross section of the sapphire single crystal is wider, which causes more bubble defects.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a sapphire single crystal growth apparatus in which bubble defects do not occur in the sapphire single crystal even when a large diameter sapphire single crystal is grown.

Sapphire single crystal growth apparatus according to an embodiment of the present invention,

A sapphire single crystal growth apparatus for growing sapphire single crystal in molten aluminum oxide, comprising: a crucible containing the aluminum oxide molten metal; A heat insulating material container in which the crucible is disposed; And a convection blocking film having an inner space (the inner space penetrates up and down) for accommodating the sapphire single crystal therein, the upper side of which is connected to the side wall of the heat insulating material container, and the lower end of which is located inside the molten metal. The convection flow of the molten metal rising from the side wall of the crucible and moving toward the sapphire single crystal is blocked by the convection blocking film and flows downward along the convection blocking film.

Sapphire single crystal growth apparatus according to another embodiment of the present invention,

A sapphire single crystal growth apparatus for growing sapphire single crystal in molten aluminum oxide, comprising: a crucible containing the aluminum oxide molten metal; A heat insulating material container in which the crucible is disposed; And a convection blocking film having an inner space (the inner space penetrates up and down) for accommodating the sapphire single crystal therein, the upper side of which is connected to the sidewall of the crucible, and the lower end of which is located inside the molten metal. The convection flow of the molten metal rising from the side wall side of the crucible and moving toward the sapphire single crystal is blocked by the convection barrier and flows downward along the convection barrier.

It is preferable that the separation distance h between the lower end of the convection blocking membrane and the lower part of the crucible is 30 to 60 mm.

The cross section of the inner space is circular, and the diameter (D1) of the inner space is preferably 1.2 to 1.3 times the diameter (d) of the final grown sapphire single crystal.

The cross section of the crucible is circular, and the inner diameter (D2) of the crucible is preferably 1.6 to 1.7 times the diameter (d) of the final grown sapphire single crystal.

In the sapphire single crystal growth apparatus according to an embodiment of the present invention, a convection blocking film is installed in the sapphire single crystal growth apparatus to block natural convection of the molten metal, and remelting the lower end surface of the sapphire single crystal by forced convection to prevent the occurrence of bubble defects in the single crystal. Decrease.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structure of the conventional sapphire single crystal growth apparatus.
2 is a diagram showing the configuration of a sapphire single crystal growth apparatus according to an embodiment of the present invention.
3 is a view showing a convection blocking film of a sapphire single crystal growth apparatus according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail through exemplary embodiments with reference to the accompanying drawings, and the present invention is not limited thereto. In addition, detailed descriptions of well-known functions and configurations that may blur the gist of the present invention will be omitted.

2 is a diagram showing the configuration of a sapphire single crystal growth apparatus 100 according to an embodiment of the present invention.

2, the sapphire single crystal growth apparatus 100 according to an embodiment of the present invention is a heat insulating material container 110, a crucible 120, a molten metal 130, a high frequency coil 140, impression bar 150, And a seed crystal 160 and a convection shield 180.

Since the remaining components except the convective barrier layer 180 have the same functions and functions as the known components used in the conventional single crystal growth apparatus, a description thereof will be omitted. Hereinafter, the convective barrier layer 180 is the single crystal growth apparatus 100. The growth process of the sapphire single crystal 170 when it is installed inside will be described.

The convection blocking layer 180 has an upper side connected to a side wall of the heat insulating material container 110, and a lower end thereof is positioned inside the molten metal 130, and the sapphire single crystal 170 is accommodated in the internal space 190. In FIG. 2, the upper side of the convection barrier layer 180 is illustrated as being connected to the heat insulating material container 110, but the upper side of the convection barrier layer 180 may be connected to the sidewall of the crucible 120.

3 is a view showing the convection blocking film 180 of the sapphire single crystal growth apparatus 100 according to an embodiment of the present invention. Referring to FIG. 3, the convection blocking film 180 has a sapphire single crystal 170 therein. It has an internal space 190 that is accommodated. The internal space 190 penetrates up and down to allow the sapphire single crystal 170 to rise upward. The interior space 190 is preferably circular, and various shapes are possible within the scope apparent to those skilled in the art. The convection blocking layer 180 may be the same material as the crucible 120, and is preferably an iridium material that is frequently used as a material of the crucible 120.

The molten metal 130 located on the sidewall of the crucible 120 heated by the high frequency coil 140 rises and is blocked by the convection blocking film 180 while flowing toward the sapphire single crystal 170 and along the convection blocking film 180. Flow down. That is, the convection blocking layer 180 blocks a natural convection flow of the molten metal 130 to form a flow like A.

The sapphire single crystal 170 rotates to guide the molten metal 130 introduced from the flow of A from the bottom of the crucible 120 to the upper side, and the molten metal 130 forms a forced convection flow such as B. The lower cross section of the growing sapphire single crystal 170 is melted by the rising hot melt 130 to form a cross section parallel to the surface of the melt 130. That is, as described in Japanese Laid-Open Patent Publication No. 2008-207992 described above, forced convection is generated without increasing the rotational speed of the sapphire single crystal 170, so that the lower end surface of the sapphire single crystal 170 can be formed in parallel. Thereby, the occurrence of bubble defects for the large diameter sapphire single crystal 170 can be reduced.

In the sapphire single crystal growth apparatus 100 according to the exemplary embodiment of the present invention, a distance h between the lower end of the convection blocking layer 180 and the bottom of the crucible 120 is preferably 30 to 60 mm. If the separation distance h is smaller than 30 mm, the high temperature molten metal 130 which exists around the sidewall of the crucible 120 may not be transferred well to the inside of the convection blocking layer 180, thereby making it difficult to control the temperature of the molten metal 130. In the case where the separation distance h is longer than 60 mm, since the amount of the molten metal 130 is decreased at the end of the growth of the single crystal 170, the surface of the molten metal 130 may be located below the convection blocking layer 180. The problem arises that the blocking effect of natural convection disappears.

In addition, the diameter D1 of the internal space 190 of the convection blocking film 180 may be 1.2 to 1.3 times the diameter d of the sapphire single crystal 170 grown finally. If the diameter D1 of the internal space 190 is smaller than 1.2 times the diameter d of the sapphire single crystal 170, the sapphire single crystal 170 may be blocked by blocking the heat emission of the sapphire single crystal 170 in which the convection blocking layer 180 grows. This is because the temperature gradient of) is not appropriately achieved and the sapphire single crystal 170 can be melted. In addition, if the diameter D1 of the internal space 190 is larger than 1.3 times the diameter d of the sapphire single crystal 170, it is expensive to manufacture the convection barrier film 180, and the convection barrier film 180 and the crucible are (120) There is a problem that the gap between the sides is narrowed to form a natural convection smoothly.

In addition, the cross section of the crucible 120 is preferably circular, the inner diameter (D2) of the crucible 120 is preferably 1.6 to 1.7 times the diameter (d) of the sapphire single crystal 170 is finally grown. If the inner diameter D2 of the crucible 120 is smaller than 1.6 times the diameter d of the sapphire single crystal 170, the gap between the side surface of the crucible 120 and the convection blocking film 180 is narrowed to smoothly form natural convection. If the inner diameter (D2) of the crucible 120 is greater than 1.7 times the diameter (d) of the sapphire single crystal 170, the cost for the manufacture of the crucible 120 is expensive.

Example  One

After filling 10 kg of aluminum oxide into a crucible 120 having an inner diameter of 170 mm, a convection block 180 as shown in FIG. 2 is positioned between the sapphire single crystal 170 and the crucible 120, and an upper insulation is placed on the convection block 180. Stacked up. Nitrogen gas was continuously injected into 2LPM during the process in order to suppress oxidation of the crucible 120 and the single crystal 170 inside the growth apparatus 100. Aluminum oxide was melted using high frequency, the c-axis seed crystal 160 was brought into contact with the molten metal 130, and then pulled up while rotating to grow the sapphire single crystal 170. At this time, the rotational speed starts with 20RPM in the shoulder process, and gradually decreases the rotational speed as the diameter grows and proceeds to 10RPM in the body process. The growth rate of the single crystal 170 was progressed to 1.0mm / hr, the pulling rate was set for each section in consideration of the decreasing amount and growth rate of the molten metal (130).

Example  2

Under the same conditions as in Example 1, only the growth rate was changed to 2.0 mm / hr, and after adjusting the pulling rate to reflect this, the single crystal 170 was grown. The higher the growth rate of the single crystal 170 tends to generate a lot of bubble defects to confirm this.

Comparative example  One

The single crystal 170 of 100 mm length was grown at a growth rate of 1 mm / hr and a rotational speed of 20 to 10 RPM in the same manner as in Example 1 without providing the convection blocking layer 180.

Comparative example  2

Under the same conditions as in Comparative Example 1, only 100 mm of single crystal 170 was grown by changing only the growth rate to 2.0 mm / hr.

The grown sapphire ingot was placed in a transparent glass bath, poured with a refractive solution having the same refractive index as sapphire, and then irradiated with light in the dark room to observe bubble defects in the sapphire ingot.

[Table 1]

The incidence of bubble defects represents the ratio of the length of the bubble generation section to the total length of the sapphire ingot. In Comparative Example 1 and Comparative Example 2, the incidence of bubble defects reached 52% and 97%, respectively, and in Example 1 and Example 2, it was confirmed that they were 0%. It can be seen that bubble defects do not occur due to the convection blocking layer 180. In addition, although the crystal defect incidence caused by partial non-uniformity of the solution composition reaches 90% in Comparative Example 2, only 10% is present in Example 2, so that the effect of reducing the crystal defect incidence caused by the convective barrier layer 180 can also be confirmed. there was.

As mentioned above, although this invention was demonstrated to the said Example, this invention is not limited to this. It will be understood by those skilled in the art that modifications and variations may be made without departing from the spirit and scope of the invention, and that such modifications and variations are also contemplated by the present invention.

10: conventional sapphire single crystal growth apparatus
100: sapphire single crystal growth apparatus according to the present invention
11, 110: insulation container
12, 120: crucible
13, 130: molten aluminum oxide
14, 140: high frequency coil
15, 150: impression rod
16, 160: seed crystal
17, 170: sapphire single crystal
180: convection barrier
190: interior space

Claims (5)

In the sapphire single crystal growth apparatus for growing sapphire single crystal in molten aluminum oxide,
A crucible containing the molten aluminum oxide;
An insulator container in which the crucible is located; And
An inner space (the inner space penetrates up and down) is formed therein to accommodate the sapphire single crystal therein, and includes a convection blocking film having an upper end connected to a side wall of the heat insulating material container and a lower end located inside the molten metal.
Sapphire single crystal growth apparatus, characterized in that the convection flow of the molten metal rising from the side wall of the crucible to move toward the sapphire single crystal is blocked by the convection blocking film and flows downward along the convection blocking film.
In the sapphire single crystal growth apparatus for growing sapphire single crystal in molten aluminum oxide,
A crucible containing the molten aluminum oxide;
An insulator container in which the crucible is located; And
An inner space (the inner space penetrates up and down) to accommodate the sapphire single crystal is formed therein, the upper side is connected to the side wall of the crucible, and the lower end includes a convection blocking film located inside the molten metal,
Sapphire single crystal growth apparatus, characterized in that the convection flow of the molten metal rising from the side wall of the crucible to move toward the sapphire single crystal is blocked by the convection blocking film and flows downward along the convection blocking film.
The separation distance (h) between the lower end of the convection blocking film and the lower part of the crucible, according to claim 1 or 2,
Sapphire single crystal growth apparatus, characterized in that 30 to 60mm.
The method according to claim 1 or 2,
The cross section of the inner space is circular,
Diameter D1 of the internal space is,
Sapphire single crystal growth apparatus, characterized in that 1.2 to 1.3 times the diameter (d) of the final grown sapphire single crystal.
The method according to claim 1 or 2,
The cross section of the crucible is circular,
The inner diameter D2 of the crucible is
Sapphire single crystal growth apparatus, characterized in that 1.6 to 1.7 times the diameter (d) of the final grown sapphire single crystal.

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