KR20140080222A - Apparatus for growing sapphire single crystal - Google Patents

Abstract

The present invention relates to an apparatus for growing a sapphire single crystal in molten alumina, including: a chamber for conducting a process for growing a sapphire single crystal; a crucible mounted inside the chamber and filled with an alumina raw material; an insulation material installed inside the chamber for accommodating the crucible; a high-frequency coil installed outside the insulation material, for melting the alumina by induction heating of the crucible; and a temperature measurement unit installed on the chamber, to measure the surface temperature during a seeding process in which a single crystal seed comes in contact with the melt.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a sapphire single-

The present invention relates to a single crystal growth apparatus, and more particularly, to a sapphire single crystal growth apparatus for growing a sapphire single crystal from a high purity alumina melt.

A sapphire single crystal (or alumina single crystal) having a lattice constant similar to that of gallium nitride (GaN) is mainly used as a substrate material in manufacturing a light emitting diode (LED) chip using a gallium nitride (GaN) compound . The Czochralski method (hereinafter referred to as CZ method), the Bernoulli method, the Kirofuros method, the EFG method, the HEM method, and the like can be used to grow the sapphire single crystal. Among them, the CZ method is advantageous in that it can grow fast crystal and monocrystal growth in the C axis direction (direction of GaN polar axis) by a typical single crystal growth method. In addition, when the single crystal grown in the C axis is processed into a wafer, the loss of the single crystal ingot can be significantly reduced compared to other a-axis growth methods.

1 is a diagram showing a procedure of a sapphire single crystal manufacturing process using the CZ method.

As shown in FIG. 1, a high purity alumina 3 as a raw material is placed in an iridium crucible 1 and completely melted (a, b, c), and a single crystal seed 5 is gradually melted (D). This process is called a seeding process (e). Thereafter, a shouldering process for growing the shoulder portion 11 simultaneously in the horizontal direction and the vertical direction to the target diameter is performed (f), and the body portion 13 is grown in the vertical direction after growing to the target diameter Boding) process is performed (g, h). Thereafter, a tailing process is performed to decrease the diameter to separate the single crystal 10 from the solution, and a cut off process is performed to completely separate the single crystal 10 from the melt after the tail process (i) . Finally, the slow cooling step in which the single crystal 10 is gradually cooled is performed (j).

The step of bringing the seed into contact with the melt in the CZ process is called a seeding process, which is a very important step in the growth of the sapphire single crystal. If the internal temperature is too high during the seeding process, the seed will melt and fall off. If this process is repeated and the seed is consumed, the seed should be cooled and then replaced with a new seed. In this case, the time spent from cooling to replacement and melting is at least 60 hours and up to 72 hours, which leads to a significant deterioration in productivity. When the internal temperature is too low, the process is prolonged while repeating the process of rapidly growing from the surface to polycrystalline in the seeding process, melting it, and contacting again. In addition, when the crystal grows due to rapid growth of the surface, There is a problem that crystal defects such as a subgrain occur.

2 is a schematic view showing a conventional sapphire single crystal growing apparatus.

As shown in FIG. 2, a conventional sapphire single crystal growing apparatus 10 induces and melts an iridium crucible 12 filled with an alumina raw material by flowing a current through a high frequency coil 14 to induce melting. In addition, a heat insulating material 13 and a chamber 11 are required to prevent the heat of the heated iridium crucible 12 from escaping to the outside and to create a condition under which the sapphire single crystal can grow.

Further, conventionally, after the alumina as the raw material is melted, the operator directly observes the molten state through the inside camera 15 provided outside the chamber 11, and thus it is difficult to maintain a constant seed touch point. Therefore, no repeatability was observed in the process time or crystal quality. The operator observes the photographed image through the monitor and observes the flow of the melt surface or the reaction of the seed in the observed images to see the image. The criterion of this judgment is ambiguous, It depends. Therefore, it is necessary to improve the repeatability of the seeding process and shorten the process time.

The present invention relates to a process for producing a sapphire single crystal which can measure the surface temperature of a melt during a seeding process in which a single crystal seed is brought into contact with a melt and shorten a seeding process time by setting an optimal temperature measurement point, Device.

The present invention relates to a sapphire single crystal growing apparatus for growing a sapphire single crystal in molten alumina, comprising: a chamber in which a process for growing a sapphire single crystal is performed; A crucible installed in the chamber and filled with alumina as a raw material; A heat insulating material installed inside the chamber and the crucible being received therein; A high frequency coil installed outside the heat insulating material and inducing heating of the crucible to melt the alumina; And a temperature measuring device installed in the chamber and measuring a surface temperature of the melt in a seeding process in which a single crystal seed is brought into contact with a melt.

Further, the temperature measuring device is fixed to a mounting table provided at the upper end of the chamber, and discloses a sapphire single crystal growing apparatus.

Also, the temperature measuring device is characterized in that the surface of the melt between the crucible and the seed opposite to the temperature measuring device is used as a temperature measurement point.

Further, the temperature measuring apparatus is characterized in that a point between the crucible and the center of the melt is set as an optimal temperature measurement point.

Also, the present invention discloses a sapphire single crystal growth apparatus characterized in that the seeding process is carried out at a surface temperature of the melt measured by the temperature meter between 2,100 and 2,200 ° C.

The sapphire single crystal growth apparatus according to the present invention is provided with a temperature measuring device for measuring the surface temperature of a melt during a seeding process in which a single crystal seed is brought into contact with a melt and repeatedly measuring fixed temperature measurement points to set optimal conditions, The process time can be shortened to improve the productivity of single crystal and to prevent the occurrence of crystal defects at the initial stage of crystal growth.

1 is a diagram showing a procedure of a sapphire single crystal manufacturing process using the CZ method.
2 is a schematic view showing a conventional sapphire single crystal growing apparatus.
3 is a schematic view of a sapphire single crystal growth apparatus according to a preferred embodiment of the present invention.
4 is a schematic view showing a temperature measuring device of a sapphire single crystal growing apparatus according to the present invention.
5 is a view schematically showing the melt temperature measurement point of the temperature measuring instrument.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

FIG. 3 is a schematic view of a sapphire single crystal growing apparatus according to a preferred embodiment of the present invention, and FIG. 4 is a schematic view of a temperature measuring apparatus of a sapphire single crystal growing apparatus according to the present invention.

3 and 4, a sapphire single crystal growth apparatus 20 according to a preferred embodiment of the present invention includes a chamber 21, a crucible 22, a heat insulating material 23, a high frequency coil 24, a camera 25 and a temperature meter 27. [

The chamber 21 is formed with predetermined processes for growing a sapphire single crystal (or an alumina single crystal) used as a substrate material in a light emitting diode (LED) chip manufacturing process using a gallium nitride (GaN) compound To provide an enclosed space. Here, the Czochralski method (hereinafter referred to as CZ method), Bernoulli method, Kirofuros method, EFG method, HEM method, and the like can be used to grow the sapphire single crystal. Among them, the present invention uses a Czochralski (Czochralski) method in which a crystal is grown by immersing a single crystal seed (Seed) 1 in an alumina oxide melt (Melt) 2 and slowly pulling it up.

The chamber 21 is formed with a shaft hole 21a through which the pulling shaft 3 for pulling up the seed 1 can pass and is provided with a camera 25 on both sides of the shaft hole 21a Viewports 21b and 21c are provided for the transmission measurement of the temperature measuring instrument 27, respectively.

The crucible 22 is installed inside the chamber 21 and filled with an alumina raw material for growing the sapphire single crystal. The alumina raw material filled in the crucible 22 is heated by the high-frequency coil 24 to become a melt 2 state. In general, iridium (Ir) is used as the material of the crucible 22.

The heat insulating material 23 is located inside the chamber 21, and the crucible 22 is accommodated therein. The heat insulating material 23 serves to prevent the heat that heats the crucible 22 from escaping to the side wall of the chamber 21 by the high frequency coil 24.

The high frequency coil 24 is installed outside the side wall of the heat insulating material 23 so that the crucible 22 can be heated by induction. The high-frequency coil 24 may be in the form of a cylindrical coil surrounding the heat insulating material 23. The configuration and operation of the high-frequency coil 24 can be understood by a known technique, and thus a detailed description thereof will be omitted. Further, the high-frequency coil 24 can be vertically shifted by a lift means (not shown) of a known technique.

The camera 25 is fixed on one side of the upper end of the chamber 21 and passes through the upper hole 23a of the heat insulating material 23 in the upper one viewport 21b of the chamber 21 to photograph the internal molten state. After the alumina as the raw material is melted, the internal melting state is photographed through the camera 25, and the operator can observe the photographed image through a monitor (not shown). At this time, the operator visually judges the flow of the surface of the melt (2) and the degree of reaction of the seed (1) among the observed images.

The temperature measuring device 27 is a pyrometer for measuring the surface temperature of the melt 2 during the seeding process in which the single crystal seed 1 is brought into contact with the melt 2. [ The pyrometer is a pyrometer used for high-temperature measurement, and the configuration of the pyrometer can be understood by a known technique, and thus a detailed description thereof will be omitted.

The temperature measuring device 27 measures the surface temperature of the melt 2 through the upper hole 23a of the heat insulating material 23 in the upper second viewport 21c of the chamber 21. [

In order to measure the optimum temperature of the surface of the melt 2 and repeatedly implement it, the temperature measurement points for the workers using the temperature measuring device 27 must be the same. The temperature measuring device 27 is fixed. Also, the temperature measuring device 27 can rotate around the hinge 28a of the mount stand 28 to adjust the measurement angle.

The temperature measuring device 27 measures the surface of the melt 2 between the side wall of the crucible 22 opposite to the temperature measuring device 27 and the single crystal seed 1 in consideration of the position of the heat insulating material 23 and the viewport 21c Point.

The temperature measurement point of the surface of the melt 2 by the temperature meter 27 will be described in detail with reference to FIG.

5 is a view schematically showing the melt temperature measurement point of the temperature measuring instrument.

5, the surface temperature measurement point of the melt 2 by the temperature meter 27 passes through the upper hole 23a of the heat insulating material 23 in the viewport 21c of the chamber 21, ) Was set at the optimum point for measuring the surface. The temperature of the surface of the melt 2 becomes excessively high when the measurement point approaches the surface of the crucible 22 because the crucible 22 itself generates heat and it is difficult to judge whether the temperature of the melt 2 is too close to the center of the melt 2, Temperature distortion due to the pulling-up shaft 1 or the pulling-up shaft 3 may occur. Thus, the temperature measurement point is fixed at the center of the crucible 22 and the center of the melt 2, that is, at the center of the radius of the crucible 22, and the measurement angle is defined by the heat insulating material 23 and the viewport 21c ), And the vertical distance between the viewport 21c and the viewport 21c was fixed at 50 mm, thereby minimizing the fluctuation of the measured value.

The fixed temperature measurement point is measured in units of 30 minutes to adjust the power value of the high frequency coil 24 so that the optimum temperature condition can be satisfied. When the seed 1 reaches the optimum temperature, the seed 1 is brought into contact with the surface of the melt 2, and if the seed 1 does not melt or grow rapidly, the seed 1 is raised while growing the single crystal. At this time, repeated experiments were carried out to find the optimal conditions. The seeding process time was measured while changing the first seed (1) touch temperature band, and the productivity was improved.

Example

The results of the experiment to find the optimum seeding temperature condition based on the temperature measured by the method proposed in the present invention are shown in the table below. First seeding was done by dividing the temperature band. Seeding type and process time were different for each temperature band.

Table 1 below is a table comparing the results of conducting the touch temperature bands during the seeding process.

Temperature (℃) Comparative Example Example Before application Below 2,100 ℃ 2,100 ~ 2,200 ℃ More than 2,200 ℃ Seeding
time 85 hours 80 hours 26 hours 132 hours Seeding
shape Not constant

다결정 급성장

Rapid polycrystalline growth

Diameter 15 ~ 20mm
Circular Seeding

Seed recording
Replace shortened length

As shown in Table 1, when the seed 1 was contacted with the surface of the melt 2 at a temperature lower than 2,100 ° C, which is the lowest temperature range, a solid film such as scorching was formed on the surface of the melt 2, The power of the high-frequency coil 24 is increased again, and a considerable time is consumed in the process.

If the temperature is higher than 2,200 ° C., the inside of the hot zone becomes too hot to melt and drop the seed 1. As a result, the length of the seed 1 becomes excessively short to proceed with the seeding process, To replace it. In this process, it took about 3 days to waste, which caused considerable waste in terms of process time.

On the other hand, when the seeding process was carried out at a temperature of 2,100 ~ 2,200 ° C, the process was completed in 26 hours, and the subsequent shouldering process was performed. As a result, the process time was improved to about 60 hours, At this time, the seeding shape was maintained as a circular shape with a diameter of 15 to 25 mm.

Therefore, a temperature measuring device 27 for measuring the temperature of the melt 2 is provided outside the chamber 21, and the temperature measurement point of the surface of the melt 2 is fixed. It was confirmed that the process time was improved when the single crystal seed (1) was brought into contact with the surface of the melt (2) when the measured temperature was 2,100-2,200 ° C.

While the present invention has been described in connection with certain exemplary embodiments, it will be understood by those skilled in the art that various changes may be made without departing from the scope of the present invention. Further, the scope of the present invention is determined by the matters set forth in the claims, and the brackets used in the claims are not used for optional limitation, but are used for specific components, .

20: Sapphire single crystal growth device
21: chamber
22: Crucible
23: Insulation
24: High frequency coil
25: Camera
27: Temperature measuring instrument
28: Cradle

Claims (5)

A sapphire single crystal growing apparatus for growing a sapphire single crystal in molten alumina,
A chamber in which a process for growing a sapphire single crystal is performed;
A crucible located inside the chamber and filled with alumina as a raw material;
A heat insulator positioned inside the chamber and containing the crucible therein;
A high frequency coil located outside the heat insulating material and inducing heating of the crucible to melt the alumina; And
And a temperature measuring device installed in the chamber and measuring a surface temperature of the melt during a seeding process in which a single crystal seed is brought into contact with a melt. The method according to claim 1,
Wherein the temperature measuring device is fixed to a mount provided at an upper end of the chamber. The method according to claim 1,
Wherein the temperature measuring device uses the surface of the melt between the crucible facing the temperature measuring device and the seed as a temperature measurement point. The method of claim 3,
Wherein the temperature measuring unit uses an equilibrium point between the crucible and the center of the melt as an optimum temperature measurement point. 2. The sapphire substrate according to claim 1,
Wherein the seeding step is carried out at a surface temperature of the melt measured by the temperature meter between 2,100 and 2,200 ° C.

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