KR101028933B1 - Single crystal melt level regulation apparatus, single crystal growth apparatus including the regulation apparatus, and single crystal melt level regulation method - Google Patents

Abstract

Disclosed are a single crystal melt level control device, a single crystal growth device having the same, and a single crystal melt level control method. The single crystal growth apparatus according to the present invention senses the temperature of a single crystal growth chamber for growing a silicon single crystal ingot and a heat shield for shielding the ingot of silicon single crystal in the single crystal growth chamber, and measures the single crystal melt level based on the temperature of the heat shield. And a single crystal melt level adjusting device for adjusting. And the single crystal melt level control apparatus according to the present invention is a temperature sensing means for detecting the temperature of the heat shield heat shielding the ingot of the silicon single crystal in the single crystal growth chamber, the lower portion of the heat shield and the silicon melt on the basis of the temperature of the heat shield Melt gap calculation means for calculating a melt gap value, which is a gap between surfaces, and control means for controlling the lifting and lowering of the crucible containing the silicon melt in accordance with the melt gap value when the melt gap value is received from the melt gap calculation means. According to the present invention as described above, since the single crystal growth apparatus controls the single crystal growth apparatus by accurately obtaining the distance between the surface of the melt and the heat shield, the stable crystal growth is possible, and the operator does not need to manually control the single crystal growth apparatus. Disappear.

Monocrystalline, Heat Shield, Melt Level, 2 Color Pyrometer

Description

Single crystal melt level control apparatus, single crystal growth apparatus and single crystal melt level control method having the same {Single crystal melt level regulation apparatus, single crystal growth apparatus including the regulation apparatus, and single crystal melt level regulation method}

The present invention relates to a single crystal growth apparatus, and more particularly, to a single crystal melt level control device, a single crystal growth device and a single crystal melt level control method having the same.

In general, in the method of growing a silicon single crystal ingot according to the Czochralski method (CZ method), polycrystalline silicon is loaded into a quartz crucible and melted polycrystalline silicon with heat radiated from a heater to form a silicon melt, and then the surface of the silicon melt Silicon single crystal ingots are grown from.

In the Czochralski method (CZ method), in order to perform crystal growth satisfactorily, it is necessary to reliably detect the liquid level (hereinafter referred to as melt level) of the raw material melt and adjust it.

In the CZ type single crystal growth apparatus, detecting and adjusting the melt level with certainty is useful for controlling the relative position of the heat shield and the melt level, or the relative position of the heater and the melt level, and promoting stable crystal growth.

By the way, in the existing CZ type silicon single crystal growth apparatus, the melt level was visually confirmed. Therefore, accurate measurement of the melt level was difficult. Conventionally, there is a method of measuring the melt level directly by using laser technology, CCD vision technology, and the like. However, this conventional method is sensitive to vibration of the melt and has a weak point to external noise.

Therefore, it is necessary to measure the melt level and adjust the melt level so as not to react sensitively to the vibration of the melt.

Accordingly, it is an object of the present invention to provide a single crystal melt level control device that senses the temperature of a heat shield heat shielding an ingot of silicon single crystal in a single crystal growth chamber and adjusts the single crystal melt level based on the temperature of the heat shield. There is.

Another object of the present invention to provide a single crystal melt level control device.

Another object of the present invention to provide a single crystal melt level control method in the single crystal growth apparatus.

According to one aspect of the present invention for achieving the above object of the present invention, a single crystal melt level control apparatus includes: temperature sensing means for sensing a temperature of a heat shield for shielding an ingot of silicon single crystal in a single crystal growth chamber; Melt gap calculation means for calculating a melt gap value, which is a gap between the lower end of the heat shield and the surface of the silicon melt based on the temperature of the heat shield; And control means for controlling the lifting and lowering of the crucible containing the silicon melt in accordance with the melt gap value when the melt gap value is received from the melt gap calculation means.

Here, the temperature sensing means may be a two color pyrometer.

Here, the control means may determine whether the melt gap value is within a predetermined threshold range, and if it is within the threshold range, maintain the crucible lift ratio with respect to the current seed lift.

Here, when the melt gap value is out of the threshold range, the control means determines the crucible elevating ratio for the seed elevating according to the calculated melt gap value, and according to the crucible elevating ratio for the seed elevating. Lifting of the crucible can be controlled.

Here, the control means may control the elevating of the crucible to reduce the crucible elevating ratio with respect to the seed elevating when the melt gap value is less than the minimum value of the threshold range.

Here, the control means may control the elevating of the crucible to increase the crucible elevating ratio to the seed elevating when the melt gap value is greater than the maximum value of the threshold range.

Here, the two-color thermometer may measure the temperature of the heat shield according to the following equation.

T = B / [A + ln (ε1 / ε2)-ln (S1 / S2)]

S1 and S2 are infrared signals collected by the two detectors included in the two-color thermometer, ε1 and ε2 are the emissivity values according to the two response wavelength bands of the two detectors, and A and B are constants determined during measurement. , T is the measured temperature value.

In addition, the single crystal growth apparatus according to an aspect of the present invention comprises a single crystal growth chamber for growing a silicon single crystal ingot; And a single crystal melt level control device that senses a temperature of a heat shield that heats the ingot of the silicon single crystal in the single crystal growth chamber and adjusts a single crystal melt level based on the temperature of the heat shield.

Here, the single crystal melt level control apparatus includes temperature sensing means for sensing a temperature of the heat shield for heat shielding the ingot of silicon single crystal in the single crystal growth chamber; Melt gap calculation means for calculating a melt gap value, which is a gap between the lower end of the heat shield and the surface of the silicon melt based on the temperature of the heat shield; And control means for controlling the lifting and lowering of the crucible containing the silicon melt in accordance with the melt gap value when the melt gap value is received from the melt gap calculation means.

Here, the temperature sensing means may be a two color pyrometer.

Here, the heat shield is formed with a hole so that the two-color thermometer can receive infrared signals from the silicon melt, and the temperature sensing means converts the infrared signal emitted through the hole into the two-color thermometer. It may include a reflector for reflecting.

In addition, the single crystal melt level control method according to an aspect of the present invention comprises the steps of sensing the temperature of the heat shield heat shielding the ingot of silicon single crystal in the single crystal growth chamber; Calculating a melt gap value, which is a distance between a bottom end of the heat shield and the surface of the silicon melt based on the temperature of the heat shield; And controlling the elevating of the crucible containing the melt in accordance with the calculated melt gap value.

The controlling of the elevating of the crucible may include determining whether the melt gap value is within a predetermined threshold range; And maintaining the crucible elevating ratio with respect to the current seed elevating when the melt gap value is within the threshold range.

Here, the step of controlling the elevating of the crucible may include: determining the crucible elevating ratio for the seed elevating according to the calculated melt gap value when the melt gap value is out of the threshold range; And controlling the crucible elevating according to the crucible elevating ratio with respect to the seed elevating.

Here, the determining of the lift ratio may include reducing the crucible lift ratio for the seed lift if the melt gap value is less than the minimum value of the threshold range.

The determining of the lift ratio may further include increasing the crucible lift ratio for the seed lift if the melt gap value is greater than the maximum value of the threshold range.

According to the single crystal melt level control device, the single crystal growth device having the same and the single crystal melt level control method as described above, in the single crystal growth device, the single crystal growth device is controlled by accurately obtaining the distance between the surface of the silicon melt and the heat shield, thereby ensuring stable crystal growth. This eliminates the need for the operator to manually control the single crystal growth apparatus.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and only the embodiments make the disclosure of the present invention complete, and the general knowledge in the art to which the present invention belongs. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

1 is a cross-sectional view schematically showing a single crystal melt level control apparatus and a single crystal growth apparatus having the same according to an embodiment of the present invention.

As shown in FIG. 1, the single crystal growth apparatus according to the exemplary embodiment of the present invention includes a chamber 10 and a single crystal melt level control device 101, and the like, and grows a silicon single crystal ingot inside the chamber 10. This is done.

The quartz crucible 30 containing the silicon melt SM is installed in the chamber 10, and a crucible support 40 made of graphite is installed outside the quartz crucible 30 so as to surround the quartz crucible 30. do.

The crucible support 40 is fixedly mounted on a pedestal 50, which is rotated by the drive means 90 to ascend while rotating the quartz crucible 30 so that the melt level is the same height. Keep it. The crucible support 40 is surrounded by a cylindrical heater 60 at predetermined intervals, which is surrounded by a radiant insulator 70.

That is, the heater 60 is installed on the side of the quartz crucible 30 to melt a high-purity polysilicon mass loaded in the quartz crucible 30 to form a silicon melt SM, and the radiant insulator 70 is a heater ( Heat dissipated in 60 is prevented from diffusing toward the wall of the chamber 10 to improve thermal efficiency.

In the upper part of the chamber 10, a pulling means 80 for winding up and pulling a cable is provided, and a seed is provided in the lower part of the cable. The pulling means 80 soaks the seed in the silicon melt SM in the quartz crucible 30 and grows the single crystal ingot IG while pulling. The pulling means 80 rotates while raising the seed during single crystal ingot IG growth. Further, the driving means 90 lifts the crucible while rotating the quartz crucible 30 in the direction opposite to the rotation direction of the single crystal ingot about the same axis as the bearing 50 of the quartz crucible 30.

In the upper portion of the chamber 10, an inert gas of argon (Ar) is supplied to the grown single crystal ingot IG and the silicon melt SM, and the used inert gas is discharged through the lower portion of the chamber 10.

A heat shield 20 may be installed between the silicon single crystal ingot IG and the quartz crucible 30 to surround the ingot IG to block heat radiated from the ingot, and the ingot IG in the heat shield 20. A cylindrical heat shield member (not shown) may be attached to the closest portion of the and may further block heat flow to conserve heat.

The heat shield 20 is installed to prevent the heat radiated from the surface of the silicon melt SM and the heater 60 from being transferred to the silicon single crystal ingot IG in order to improve the productivity and quality of the silicon single crystal ingot IG. It is essential to install recently. And, when installing the heat shield 20, while maintaining a constant distance (D) between the lower end of the heat shield 20 and the surface (Melt Level: ML) of the silicon melt (SM), the space (D) is installed It is called a melt gap (D).

The melt gap D becomes a flow path of argon (Ar) gas injected from the upper part of the silicon single crystal growth furnace and discharged to the lower part during the silicon single crystal growth, and also affects the thermal history of the silicon single crystal ingot (IG). do. Therefore, when the silicon single crystal ingot IG is grown, the melt gap D must be constantly maintained for quality improvement and productivity of the silicon single crystal ingot IG.

In order to keep this melt gap constant, the observation opening 4 is formed in the upper part of the chamber 10 by an operator so that the inside of a single crystal growth apparatus can be observed.

The present invention includes a single crystal melt level control device 101 that senses the temperature of the heat shield 20 and adjusts the melt level based on the temperature of the heat shield, wherein the single crystal melt level control device 101 comprises a heat shield 20. Seed so that the melt level can be adjusted according to the temperature sensing means 100 for detecting the temperature of the heat sink, the melt gap calculating means 110 for calculating the melt gap corresponding to the temperature of the heat shield 20, and the melt gap D. And control means 120 for controlling the crucible lifting for lifting.

The temperature sensing means 100 senses the temperature of the heat shield 20 through the observation opening 4. This is because the temperature of the heat shield 20 indicates how close the silicon melt is to the heat shield 20. When the heat shield 20 is close to the melt, the heat shield 20 receives heat from the melt and the temperature thereof rises. In addition, when the heat shield 20 is away from the melt, the heat shield 20 receives less heat from the melt, and thus the temperature drops.

As such, the melt level can be obtained by measuring the temperature of the heat shield 20 installed to surround the ingot IG between the silicon single crystal ingot IG and the quartz crucible 30. That is, by measuring the temperature of the heat shield 20, it is possible to know the melt level according to the temperature of the heat shield 20.

Therefore, the temperature sensing means 100 according to the present invention detects the temperature of the heat shield 20. The temperature sensing means 100 is preferably a two color pyrometer (hereinafter referred to as '100').

The two-color thermometer 100 is a non-contact infrared thermometer. Non-contact infrared thermometers measure temperature without making physical contact with the object. These non-contact infrared thermometers are based on the fact that all objects emit IR energy, and the density of radiation is a function of temperature. In particular, infrared dichroic thermometers have outstanding accuracy and functional differences that are markedly different in many respects from typical sensors of non-contact infrared thermometers.

The two-color thermometer 100 includes two brightness proportional pyrometers in one package. The two detectors operate at two different wavelengths, but measure the energy from one target. That is, the two-color thermometer 100 compares two signal values measured by two detectors having different wavelength ranges, and calculates a measured temperature value. Accordingly, the two-color thermometer 100 has a much more accurate advantage with respect to the change in emissivity of the target object than, for example, a one color sensor. If the signals received by the two detectors of the two-color thermometer 100 are called S1 and S2, and the two emissivity values according to the two response wavelengths of each detector are ε1 and ε2, the temperature value measured by the two-color thermometer is expressed by the following equation. It can be represented as 1.

T = B / [A + ln (ε1 / ε1)-ln (S1 / S2)]

A, B: Constant determined during measurement, T: Measured temperature value

The measured temperature value is determined by the ratio of the two signals (S1 / S2) and the ratio of the two emissivity (ε1 / ε2). Less sensitive to severe metals, etc.).

Due to this measuring principle, the two-color thermometer 100 has the following advantages. Specifically, the two-color thermometer 100 measures the temperature accurately even if the object to be measured by the obstacle is partially covered (intermittently or permanently). This is because the signals S1 and S2 received by the two detectors of the two-color thermometer 100 decrease at the same rate when the measurement part is covered. In addition, the two-color thermometer 100 accurately measures the temperature of the target object even if the target object is covered by smoke, dust, large particles of dust, etc. in the air. In addition, the two-color thermometer 100 accurately measures the temperature of the target object even when foreign matters accumulate on the lens of the detector. In addition, the two-color thermometer 100 measures an accurate temperature even if the object to be measured is smaller than the measuring size of the sensor (eg, a wire). have. In this case, the heat shield, which is the measurement object, is preferably made of graphite, because the graphite has excellent heat absorption.

As such, according to the present invention, the two-color thermometer 100 senses the temperature of the heat shield 20, and senses the temperature of the lower end located close to the silicon melt of the heat shield 20. This will be described in detail with reference to FIG. 2.

2 is a side cross-sectional view of a heat shield according to an embodiment of the present invention.

Referring to FIG. 2, the temperature of the heat shield 20 measured by the two color thermometer 100 is measured at position P1 on the heat shield 20. Since the position P1 on the heat shield 20 is close to the silicon melt SM, the temperature of the melt is well transmitted. In addition, the position P1 on the heat shield 20 is a position measurable by the two-color thermometer 100. However, the position P2 of the heat shield 20 is more sensitive to the temperature of the melt than the position P1.

3 is a diagram illustrating a temperature distribution of a heat shield according to the distance between the heat shield and the silicon melt. FIG. 3 (a) shows the case where the melt gap, which is the distance between the heat shield and the silicon melt, is 30, FIG. 3 (b) shows the case where the melt gap is 40, and FIG. 4 (d) shows the case where the melt gap is 50. Indicates. 4 is a graph showing the temperature of the points of the heat shield according to the melt gap.

3 and 4, it can be seen that the temperature of the heat shield 20 according to the melt gap D is more sensitive to the melt gap D than the position P1 on the heat shield 20. In other words, the temperature at the position P2 on the heat shield 20 changes more as the melt gap D changes than the position P1.

Therefore, according to another embodiment of the present invention, the two-color thermometer 100 forms a single crystal growth apparatus so that the position P2 of the heat shield 20 can be measured.

5 is a sectional view showing a single crystal growth apparatus according to another embodiment of the present invention.

Referring to FIG. 5, a hole 2 is formed in the heat shield 20 so that the temperature sensing means 100 can sense the temperature.

In addition, the temperature sensing means 100 collects infrared energy coming out of the melt through the hole 2. Since the infrared ray is straight, the single crystal growth apparatus is provided with a reflecting plate 22 for reflecting the infrared ray traveling straight through the hole 2 of the heat shield 20 to the two-color thermometer 100. Thus, the two-color thermometer 100 can collect infrared radiation emitted from the melt through the apertures 2 of the heat shield 20.

Referring back to FIG. 1, the two-color thermometer 100 measures the temperature of the object, that is, the heat shield 20, and provides the melt gap calculation means 110. The melt gap calculation means 110 calculates a melt gap D, which is a gap between the lower end of the heat shield 20 and the surface of the silicon melt SM, from the measured temperature. The relationship between the temperature of the heat shield 20 and the melt gap D is stored in advance in the melt gap calculating means 110. The melt gap calculation unit 110 may store, for example, a table corresponding to the melt gap D value corresponding to the temperature of the heat shield 20. In another embodiment, the melt gap calculation unit 110 may calculate the melt gap D value by using a predetermined equation using the temperature of the heat shield 20. In this case, variables related to the surrounding environment may be considered.

The melt gap calculation means 110 calculates the melt gap value from the temperature of the heat shield 20 and provides the calculated cement gap value to the control means 120. The control means 120 may be implemented as a programmable logic controller (PLC). In addition, the melt gap calculation means 110 may be included in the control means 120. The control means 120 controls the driving means 90 for elevating the crucible 30 according to the melt gap when receiving the melt gap D value from the melt gap calculating means 110. The detailed operation of the control means 120 will be described with reference to FIG. 6.

6 is a flowchart illustrating a method of adjusting a single crystal melt level according to the present invention.

Referring to FIG. 6, the single crystal melt level adjusting apparatus 101 first determines whether a temperature value of the heat shield 20 is received from the two-color thermometer 100 in step 301. When the temperature of the heat shield 20 is received, the single crystal melt level adjusting apparatus 101 calculates the melt gap D according to the temperature value of the heat shield 20 in step 303.

As described above, in the present embodiment, the relationship between the temperature of the heat shield 20 and the melt gap D may be stored in advance in the single crystal melt level adjusting device 101.

Subsequently, the single crystal melt level adjusting apparatus 101 determines whether the melt gap D value is within a predetermined threshold range in step 305. This critical range is such that the relative positional relationship between the bottom surface of the optimal heat shield 20 and the molten silicon surface, that is, the melt gap D, causes the thermal history and impurity concentration (oxygen concentration, etc.) of the pulled silicon single crystal to be constant. Range.

If the melt gap D value is within this threshold range, there is no need to change the crucible lift ratio for quartz seed lift. This threshold range includes the optimal melt gap (D) value. If the quartz crucible 30 is moved so that the melt gap D is optimal, the elevating ratio of the crucible to the seed elevating may be continuously changed. Therefore, if the melt gap is within this threshold range, the single crystal melt level adjusting device 101 maintains the ascent rate of the quartz crucible 30 as it is now. That is, the single crystal melt level adjusting device 101 maintains the crucible lifting ratio with respect to the current seed lifting and controls the lifting of the crucible 30 according to the current ratio.

If the melt gap D value is out of the threshold range, the single crystal melt level adjusting device 101 determines the crucible 30 lifting rate for seed lifting according to the melt gap calculated in step 307, and seeding in step 309. The crucible lifting is controlled according to the crucible 30 lifting rate for lifting.

Specifically, the single crystal melt level control device 101 controls the crucible 30 lifting to maintain the melt gap D value within the predetermined range during single crystal growth. Specifically, when the melt gap D value is smaller than the minimum value of the predetermined threshold range, the single crystal melt level adjusting device 101 drives to elevate the crucible 30 to reduce the crucible 30 lifting ratio for seed lifting. Control means 90. Further, when the melt gap D value is larger than the maximum value of the predetermined threshold range, the single crystal melt level adjusting device 101 drives the crucible 30 to elevate the crucible 30 to increase the rate of elevating the crucible 30 to the seed lift. Control 90.

In another embodiment, the single crystal melt level adjusting device 101 includes driving means for raising the quartz crucible 30 such that the crucible 30 lifting ratio for seed lifting is the crucible 30 lifting ratio for the determined seed lifting. 90, as well as the raising means 80 for raising and lowering the seed.

As described above, according to the present invention, the melt level can be adjusted by using the temperature of the heat shield 20 of the single crystal growth apparatus.

Although described with reference to the embodiments above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

1 is a schematic cross-sectional view of a single crystal growth apparatus having a single crystal melt level control apparatus according to an embodiment of the present invention.

2 is a side cross-sectional view of a heat shield according to an embodiment of the present invention.

3 is a diagram showing a temperature distribution of a heat shield according to the distance between the heat shield and the heat shield melt.

4 is a graph showing the temperature of the points of the heat shield according to the melt gap.

5 is a sectional view showing a single crystal growth apparatus according to another embodiment of the present invention.

6 is a flowchart illustrating a method of adjusting a single crystal melt level according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: chamber 20: heat shield

30: quartz crucible 60: heater

100: two-color thermometer 110: melt gap calculation means

120: control means

Claims (16)

Temperature sensing means for sensing a temperature of a heat shield for shielding the ingot of silicon single crystal in the single crystal growth chamber; Melt gap calculation means for calculating a melt gap value, which is a gap between the lower end of the heat shield and the surface of the silicon melt based on the temperature of the heat shield; And And control means for controlling the lifting and lowering of the crucible containing the silicon melt in response to receiving the melt gap value from the melt gap calculating means. The method of claim 1, The temperature sensing means is a single crystal melt level adjusting device, characterized in that the two-color thermometer (2 color pyrometer). The method of claim 1, And the control means determines whether the melt gap value is within a predetermined threshold range, and maintains the crucible elevating ratio with respect to the current seed lift if it is within the threshold range. The method of claim 3, When the melt gap value is out of the threshold range, the control means determines the crucible elevating ratio for the seed elevating according to the calculated melt gap value, and determines the crucible elevating ratio for the seed elevating. A single crystal melt level adjustment device, characterized in that the lifting control. The method of claim 4, wherein And the control means controls the raising and lowering of the crucible so as to reduce the crucible elevating ratio with respect to the seed elevating when the melt gap value is smaller than the minimum value of the threshold range. The method of claim 4, wherein And the control means controls the raising and lowering of the crucible so as to increase the crucible elevating ratio with respect to the seed elevating when the melt gap value is greater than the maximum value of the threshold range. The method of claim 2, The two-color thermometer is a single crystal melt level control device for measuring the temperature of the heat shield according to the following equation. T = B / [A + ln (ε1 / ε2)-ln (S1 / S2)] S1 and S2 are infrared signals collected by the two detectors included in the two-color thermometer, ε1 and ε2 are the emissivity values according to the two response wavelength bands of the two detectors, and A and B are constants determined during measurement. , T is the measured temperature value. A single crystal growth chamber for growing a silicon single crystal ingot; And And a single crystal melt level control device that senses a temperature of a heat shield heat shielding the ingot of the silicon single crystal in the single crystal growth chamber and adjusts the single crystal melt level based on the temperature of the heat shield. Growth device. The method of claim 8, The single crystal melt level adjusting device, Temperature sensing means for sensing a temperature of said heat shield for thermally shielding an ingot of silicon single crystal in said single crystal growth chamber; Melt gap calculation means for calculating a melt gap value, which is a gap between the lower end of the heat shield and the surface of the silicon melt based on the temperature of the heat shield; And And a control means for controlling the lifting and lowering of the crucible containing the silicon melt in accordance with the melt gap value when the melt gap value is provided from the melt gap calculation means. 10. The method of claim 9, The temperature sensing means is a single crystal growth apparatus, characterized in that the two-color thermometer (2 color pyrometer). The method of claim 10, The heat shield is formed with a hole to allow the two-color thermometer to receive infrared signals from the silicon melt, The temperature sensing means further comprises a reflector for reflecting the infrared signal emitted through the hole to the two-color thermometer. Sensing a temperature of a heat shield for thermally shielding the ingot of silicon single crystal in the single crystal growth chamber; Calculating a melt gap value, which is a distance between a bottom end of the heat shield and the surface of the silicon melt based on the temperature of the heat shield; And And controlling the lifting and lowering of the crucible to accommodate the melt in accordance with the calculated melt gap value. The method of claim 12, Controlling the elevating of the crucible Determining whether the melt gap value is within a predetermined threshold range; And And maintaining the crucible elevating ratio with respect to the current seed elevating if the melt gap value is within the threshold range. The method of claim 13, The step of controlling the lifting of the crucible, Determining the crucible elevating ratio for the seed elevating according to the calculated melt gap value if the melt gap value is out of the threshold range; And And controlling the crucible elevating according to the crucible elevating ratio with respect to the seed elevating. The method of claim 14, Determining the lift ratio, And reducing the crucible elevating ratio for the seed elevating if the melt gap value is less than the minimum value of the threshold range. The method of claim 15, Determining the lift ratio, And increasing the crucible elevating ratio for the seed elevating when the melt gap value is greater than the maximum value of the threshold range.

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