KR20120058330A - Apparatus for manufacturing polysilicon based electron-beam melting using dummy bar and method of manufacturing polysilicon using the same - Google Patents

Abstract

PURPOSE: A poly-silicon manufacturing device and method of electronic beam melting base are provided to maximize elimination efficiency of metallic impurities by applying a dummy bar when unidirectionally coagulating molten silicon. CONSTITUTION: The inside of a vacuum chamber(110) is maintained under high-vacuum atmosphere. A first electron gun(120a) and a second electron gun(120b) radiate electron beam in the inner side of the vacuum chamber. A silicon melting unit(130) is arranged is arranged in a first electron beam radiation area. A one-way solidification unit(140) is arranged in a second first electron beam radiation area. The one-way solidification unit comprises a start block(145) transferring molten silicon to a down direction.

Description

Apparatus and method for manufacturing polysilicon based on electron beam melting using a dummy bar

The present invention relates to a polysilicon manufacturing technology, and more particularly, in performing silicon casting based on an electron-beam melting method, using a dummy bar that can improve the silicon refining effect by using a dummy bar. An electron beam melting based silicon fabrication apparatus and method are disclosed.

The purity of silicon is usually expressed as 2N, 3N, 6N, 11N or the like. Here, the number before 'N' means the number of 9 in the weight unit, 2N means 99% purity, and 6N means 99.9999% purity.

In the case of semiconductor grade silicon requiring ultra high purity, the purity reaches 11N. However, silicon used as a raw material of the photovoltaic cell is known to obtain a light conversion efficiency similar to that of applying silicon of 11N, even at a purity of 5N to 7N, which is relatively lower than that of semiconductor-grade silicon, 11N.

Semiconductor grade silicon is manufactured through a chemical gasification process. However, the silicon manufacturing process is known to generate a large amount of contaminants, low production efficiency, and high production cost.

Accordingly, the silicon used as a raw material of the solar cell is difficult to apply the semiconductor-grade silicon manufacturing process, and the metallurgical refining process that can mass-produce high purity silicon at low manufacturing cost has been actively developed.

Metallurgical refining of high-purity silicon for solar power generation has been developed such as vacuum refining, wet refining, oxidation, and unidirectional solidification refining, and some of them are commercially available.

Among these metallurgical refining methods, silicon manufacturing technology by metal melting method such as vacuum refining method and unidirectional coagulation refining method is easy to control characteristics, and active research is being conducted because there is little contamination by impurities during operation.

Here, the vacuum refining method is a refining process that removes impurities having a lower boiling point and vapor pressure from the molten metal than the silicon after melting the metal raw material. It is a refining process that segregates impurities into liquid along the liquid interface.

An object of the present invention is to provide an electron beam melting-based silicon manufacturing apparatus using a dummy bar in the electron beam melting-based polysilicon manufacturing apparatus, which can improve the silicon refining efficiency by using a dummy bar.

Another object of the present invention is to provide an electron beam melting-based polysilicon manufacturing method using a dummy bar that can maximize the removal of metal impurities by controlling the driving of the dummy bar.

Electron beam melting-based polysilicon manufacturing apparatus according to an embodiment of the present invention for achieving the above one object is disposed on the top of the vacuum chamber, the first and second electron gun for irradiating the electron beam (electron beam) into the vacuum chamber ( electron-gun); A silicon melting part disposed in the first electron beam irradiation region by the first electron gun, wherein a silicon raw material is charged and melted by the first electron beam; And a start block disposed in the second electron beam irradiation area by the second electron gun to maintain the molten state of the molten silicon supplied from the silicon melting part, and to be driven downward in the inside to transfer the molten silicon in the downward direction. and a one-way solidification unit in which a cooling channel is formed at a lower side thereof to solidify and cast the molten silicon from the bottom to the upper direction thereof. The start block includes a dummy bar having a silicon button bonded to the top thereof. It is characterized by including a (dummy bar).

Polysilicon manufacturing method according to an embodiment of the present invention for achieving the above another object comprises the steps of providing a polysilicon manufacturing apparatus comprising a silicon melting portion to form molten silicon, and a unidirectional solidification portion is cast molten silicon; Mounting a dummy bar of graphite material inside the one-way solidification unit; Manufacturing a start block inside the one-way solidification part through melting of the silicon button on the dummy bar; Feeding a silicon raw material in the form of particles into the silicon melting part and melting the silicon raw material fed by electron beam irradiation; The molten silicon overflows while feeding the silicon raw material and melting of the fed silicon raw material continuously; The molten silicon overflowed from the one-way solidification part is supplied, the molten silicon is transferred to the lower part by driving the start block downward while maintaining the molten state by electron beam irradiation, and then the lower part of the molten silicon is cooled to the upper direction. Refining through solidification; And cutting the upper portion of the refined silicon to remove metal impurities on the upper portion of the refined silicon.

The apparatus and method for producing polysilicon based on electron beam melting using a dummy bar according to the present invention may remove volatile impurities through vacuum refining using a first electron beam.

In particular, the polysilicon manufacturing apparatus according to the present invention has an advantage of maximizing the removal efficiency of metal impurities by easily controlling the behavior of molten silicon by applying a dummy bar during unidirectional solidification of molten silicon.

Therefore, the silicon cast using the apparatus and method according to the present invention can be utilized as silicon for solar power generation by having a purity of 5N ~ 7N class.

Figure 1 schematically shows an apparatus for producing polysilicon based on electron beam melting that can be applied to the present invention.
2 schematically shows an example of a start block including a dummy bar according to an embodiment of the present invention.
Figure 3 schematically shows a method for producing polysilicon based on electron beam melting that can be applied to the present invention.
Figure 4 shows an example of a liquid-liquid interface formed by the electron beam pattern applied to the present invention.
FIG. 5 shows a cross-sectional view of a cast silicon cross section when a start block in which a graphite dummy bar and a silicon button are bonded is applied.
FIG. 6 shows a cast silicon cross section when a start block using only graphite dummy bars is applied.
Figure 7 shows a silicon photo cast by the process according to the embodiment.
8 is a photograph showing a cross section of an impurity concentration boundary portion in silicon cast by the process according to the embodiment.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the examples described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the examples disclosed below, but may be implemented in various forms, and only the examples are intended to complete the disclosure of the present invention and those skilled in the art to which the present invention pertains. It is provided to fully inform the scope of the invention, and the invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, an apparatus and method for manufacturing polysilicon based on electron beam melting using a dummy bar according to the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 schematically shows an apparatus for producing polysilicon based on electron beam melting that can be applied to the present invention.

Referring to FIG. 1, the illustrated electron beam melting-based polysilicon manufacturing apparatus includes a vacuum chamber 110, two electron guns including a first electron gun 120a and a second electron gun 120b, and silicon. Melting unit 130 and one-way solidification unit 140 is included.

The vacuum chamber 110 melts the silicon raw material and maintains the interior in a high vacuum atmosphere while casting molten silicon. The pressure inside the vacuum chamber 110 may be about 10 ⁻⁵ torr.

The first electron gun 120a and the second electron gun 120b are disposed above the vacuum chamber 110 so that an electron beam is irradiated into the vacuum chamber 110.

The silicon melter 130 is disposed in a region where the first electron beam is irradiated by the first electron gun 120a. In the silicon melting unit 130, the silicon raw material in the form of particles is charged from the raw material supply device 101, and the loaded silicon raw material is melted by the first electron beam accelerated and integrated by the first electron gun 120a.

In this case, the first electron gun 120a preferably accelerates and integrates the first electron beam such that the first electron beam has an output energy of 4000 kW / m ² or less, approximately 2000 to 4000 kW / m ² . When the output energy of the first electron beam exceeds 4000 kW / m ² , the molten metal may be unstable because the molten metal splashes out of the crucible by the electron beam.

The silicon melter 130 is preferably provided with a water-cooled crucible capable of blocking the inflow of impurities from the crucible which may occur during the operation and easily controlling the cooling efficiency.

The one-way solidification unit 140 continuously casts molten silicon and at the same time induces segregation of metal impurities to improve silicon refining efficiency. The one-way solidification unit 140 is disposed in a region where the second electron beam is irradiated by the second electron gun 120b and is connected to the silicon melting unit 130 through the water flow path 135. As the silicon raw material is continuously charged into the silicon melter 130, the amount of molten silicon formed in the silicon melter 130 increases. Accordingly, the molten silicon overflowed from the silicon melter 130 is supplied to the one-way solidification unit 140 through the water flow passage 135.

In addition, a cooling channel 142 is formed below the one-way solidification unit 140 to which cooling water or the like for cooling the molten silicon is supplied. In addition, a start block 145 driven in the downward direction is mounted inside the one-way solidification unit 140.

The start block 145 is driven downward in the one-way solidification unit 140 and serves to physically transfer the molten silicon to the bottom while growing a mold for silicon casting. The start block 145 may be in the form of a dummy bar to which high purity silicon buttons are bonded to prevent graphite contamination of the cast silicon.

In the one-way solidification unit 140, the molten silicon supplied from the silicon melting unit 130 is maintained by the start block 145 in a state in which the molten silicon is maintained by the second electron beam accelerated and integrated by the second electron gun 120a. After being transferred downward, it solidifies and casts upward through the cooling channel 142.

The second electron gun 120b may accelerate and integrate the second electron beam such that the second electron beam has an output energy of 1000 to 2000 kW / m ² . When the output energy of the second electron beam is less than 1000 kW / m ² , it is difficult to maintain the molten state of silicon. When the output energy of the second electron beam exceeds 2000 kW / m ² , the molten metal splashes out of the crucible by the electron beam. The problem that the melt behavior becomes unstable may occur. Such unstable melt behavior also affects the overflow process control from the molten portion. The one-way solidification portion 140 may include a casting vessel made of copper having a cooling channel similar to the water freezing crucible.

2 schematically shows an example of a start block including a dummy bar according to an embodiment of the present invention.

Referring to FIG. 2, the start block 145 may use a high purity silicon button 147 bonded to a dummy bar 146.

The silicon button 147 may have a thickness of about 8N to 10N and about 10 to 15 mm in purity, and the silicon chunk is melt-bonded to the dummy bar 146 by the second electron beam inside the one-way solidification unit 140. Can be.

The dummy bar 146 may be formed of a graphite material. In particular, as the material of the dummy bar 146, low density graphite is most preferable. When low density graphite is used as the material of the dummy bar, the silicon molten metal penetrates into the porous surface of the graphite to solidify and bonds strongly to the dummy bar, and prevents rapid temperature deviation between the lower cooling device and the initially formed melt. Can function.

The reason for using the silicon button 147 instead of the dummy bar 146 as the stab block 145 is that when the dummy bar 146 is applied, contamination problems such as graphite contamination of the cast silicon may occur. Because it can.

Thus, the silicon button 147 serves to prevent contamination from graphite by preventing the dummy bar 146 from directly contacting molten silicon or cast silicon.

Figure 3 schematically shows a method for producing polysilicon based on electron beam melting that can be applied to the present invention.

Referring to Figure 3, the polysilicon manufacturing method according to the present invention is a polysilicon manufacturing apparatus preparing step (S310), the dummy bar mounting step (S320), a start block manufacturing step (S330) by melting the silicon button, low-purity silicon feeding And a melting step S340, an overflow step S350 of the molten metal, a refining step S360 through silicon solidification, and a silicon upper cutting step S370.

In the polysilicon manufacturing apparatus preparing step (S310), as shown in FIG. 1, the molten silicon material is melted after melting the silicon raw material, including a vacuum chamber, a first electron gun, a second electron gun, a silicon melting part, and a unidirectional solidification part. The polysilicon manufacturing apparatus which can cast is provided.

In the dummy bar mounting step (S320), the dummy bar is mounted inside the one-way solidification part. Then, in the start block manufacturing step (S330) to manufacture a start block by melting the silicon button.

Mounting of the dummy bar may be performed by the following procedure.

First, a dummy bar made of graphite material is mounted inside the one-way solidification unit 140. Thereafter, silicon chunks are put on the dummy bar. Next, the silicon chunk is melt-bonded to the dummy bar by a second electron beam in a vacuum atmosphere of about 10 ⁻⁵ torr. Through this process, a start block in which an upper silicon button and a lower dummy bar of graphite material is bonded to each other is formed.

Next, in the silicon melting step (S430), the silicon raw material in the form of particles is charged to the silicon melting unit, and the first electron beam is irradiated with the first electron gun to melt the charged silicon raw material. As the silicon raw material loaded into the silicon melting part, a silicon raw material having a purity of 2N and an average particle diameter of 1 to 2 mm may be used.

As the silicon raw material is melted by the first electron beam, volatile impurities such as aluminum (Al), calcium (Ca), phosphorus (P), magnesium (Mg), manganese (Mn), and the like included in the silicon raw material are volatilized in vacuum. .

Volatile impurities having a lower boiling point and vapor pressure than silicon are volatilized by high vacuum and high heating temperature by the first electron beam. In this case, when the first electron beam output energy is increased and the first electron beam irradiation time is increased, refining efficiency may be improved.

In the step S340, the first electron beam may be accelerated and integrated in the first electron gun so that the first electron beam has an output energy of about 4000 kW / m ² to facilitate silicon melting and volatile impurities removal.

Next, in the overflow step (S350) of the molten metal, the silicon raw material is continuously fed to the molten silicon, and the amount of molten silicon formed in the molten silicon increases, while the molten silicon overflows and flows in one direction through the molten metal. It is supplied to the coagulation part.

Next, in the refining step (S360) through silicon coagulation, the molten silicon overflowed from the silicon melting part is supplied from the one-way solidification part, and the molten silicon supplied by irradiating the second electron beam with the second electron gun is maintained. After the start block having an internal dummy bar is driven downward to transfer the molten silicon in the downward direction, the lower portion of the molten silicon is cooled so that the molten silicon is solidified and solidified simultaneously from the bottom to the upper direction.

In the step S360, the second electron beam may accelerate and accumulate the second electron beam in the second electron gun so that the silicon supplied from the silicon melting part maintains the molten state by having an output energy of 1000 to 2000 kW / m ² . have.

On the other hand, the start block having a dummy bar in the step S360 may be driven to descend at a rate of 0.005 ~ 0.05 mm / s. If the start block falls at a speed of less than 0.005 mm / s, the level of the silicon melt continuously rises and process control is impossible. If the start block falls below 0.05 mm / s, the melt level is continuously lowered. There is a problem that the molten metal leaks to the lower one-way solidification.

In this process, metal impurities such as iron (Fe), nickel (Ni), titanium (Ti), chromium (Cr), and copper (Cu) included in the molten silicon are moved upward along the solid-liquid interface. The segregation effect of such impurities can be sufficiently exhibited when the temperature difference between the solid and liquid is high while maintaining the interface between the solid phase 420 and the liquid phase 410 perpendicular to the growth direction during the silicon solidification process, as shown in the example shown in FIG. 4. have.

In the present invention, by using the start block having the dummy bar in the one-way solidification portion, the molten silicon of the molten silicon by the second electron beam can be kept relatively long, and the behavior of the molten silicon can be easily controlled through the start block having the dummy bar. The impurity segregation effect along the solid-liquid interface can be improved.

Next, in the silicon upper cutting step (S370) to cut the upper portion of the cast silicon. As the metal impurity contained in the molten silicon moves upward along the solid-liquid interface, segregation of the metal impurity is concentrated at the top of the cast silicon, as shown in FIG. 8. Therefore, by cutting off the portion to a certain length, it is possible to produce a high-purity polysilicon.

In the embodiment of the present invention, the final polysilicon is approximately 100 mm in diameter, the height of the operation time, the growth rate can be 1 ~ 1000 mm by adjusting the growth rate. At this time, the process was controlled so that the height of the upper portion where the impurities were concentrated was less than 20% of the total specimen height.

Silicon cast through the above process may have a purity of 5N ~ 7N, it can be usefully used as silicon for solar power generation.

Example

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

First, polysilicon was prepared by the following procedure.

A graphite dummy bar was placed in the one-way solidification unit, charged with a silicon mass of 9N purity and mass of 180g, and then the vacuum atmosphere was 10-5 torr, and the electron beam was discharged at 2000 kW / m ² using a second electron gun. Irradiation for 10 minutes melted the silicon and bonded to the dummy bottom bar.

Silicon particles of 1 to 10 mm size supplied to the water-cooling crucible through the raw material supply device were supplied to the molten silicon and simultaneously irradiated the first electron beam with an output energy of 1000 to 1500 kW / m ² using the first electron gun. .

Then, the molten silicon is supplied to the one-way solidification unit along the waterway, and the second electron beam is irradiated with an output energy of 1000 to 2000 kW / m ² using a second electron gun to start the molten state of silicon. After the block was lowered at a rate of 0.005 to 0.05 mm / s, the start block was cooled.

5 is a cross-sectional view showing a polysilicon cross section prepared when a graphite dummy bar and a start block are bonded to a silicon button, and FIG. 6 shows a cross section of polysilicon prepared when a start block using only a graphite dummy bar is applied.

5 and 6, it can be seen that the polysilicon produced when the start block is bonded to the graphite dummy bar and the silicon button is significantly less graphite contamination than when only the dummy bar of graphite alone is used.

7 is a view showing a polysilicon picture prepared by the process according to the embodiment, Figure 8 is a picture showing a cross section of the impurity concentration portion upper portion of the polysilicon prepared by the process according to the embodiment.

Referring to FIGS. 7 and 8, it can be seen that metal impurities and the like move to the top of the ingot while polysilicon is manufactured.

Table 1 shows the results of purity analysis of the impurity layer and the refined layer by ICP-AES analysis of the polysilicon prepared according to the embodiment.

[Table 1] (Unit: ppm)

Referring to Table 1, as a result of manufacturing polysilicon using an electron beam melting-based polysilicon manufacturing apparatus using a dummy bar according to the present invention, it can be seen that the silicon raw material of 2N purity is refined to 6N purity, and impurities are It can be seen that it is concentrated in the uppermost impurity layer.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and those skilled in the art to which the art belongs can make various modifications and other equivalent embodiments therefrom. I will understand.

Therefore, the true technical protection scope of the present invention will be defined by the claims below.

110: vacuum chamber 120a: first electron gun
120b: second electron gun 130: silicon melt
135: Tango 140: one-way solidification unit
142 cooling channel 145 start block
146: Dummy Bar 147: Silicon Button
S310: polysilicon manufacturing device arrangement step
S320: Dummy Bar Mounting Steps
S330: Start Block Manufacturing Steps
S340: Low purity silicon feeding and melting step
S350: overflow stage of the molten metal
S360: refining step through silicon solidification
S370: Silicon Top Cutting Step

Claims (13)

First and second electron-guns disposed above the vacuum chamber and irradiating electron beams into the vacuum chamber;
A silicon melting part disposed in the first electron beam irradiation region by the first electron gun, wherein a silicon raw material is charged and melted by the first electron beam; And
A start block disposed in a second electron beam irradiation region by the second electron gun to maintain a molten state of molten silicon supplied from the silicon melting unit, and to be driven downward in the inside to transfer molten silicon in a downward direction; And a one-way solidification unit in which a cooling channel is formed at a lower side thereof so that the molten silicon is solidified and casted from the bottom to the upper direction thereof.
The start block, the electron beam melting-based polysilicon manufacturing apparatus, characterized in that it has a dummy bar (silicon bar) is bonded to the upper portion.
The method of claim 1,
The second electron gun
Electron beam melting-based polysilicon manufacturing apparatus, characterized in that for accelerating and integrating the second electron beam so that the second electron beam has an energy of 1000 ~ 2000 kW / m ² .
The method of claim 1,
The one-way solidification unit
Electron beam melting-based polysilicon manufacturing apparatus characterized in that it comprises a casting vessel made of copper formed with a cooling channel on the lower side.
The method of claim 1,
The silicone button
Electron beam melting-based polysilicon manufacturing apparatus having a purity of 8N ~ 10N, 10 ~ 15mm thickness.
The method of claim 1,
The silicone button
An apparatus for manufacturing electron beam melting-based polysilicon, wherein a silicon chunk is melt-bonded to the dummy bar by the second electron beam inside the one-way solidification unit.
The method of claim 1,
The dummy bar is
Electron beam melting-based polysilicon manufacturing apparatus, characterized in that the graphite (graphite) material.
Providing a polysilicon manufacturing apparatus including a silicon melter to form molten silicon and a unidirectional solidified part to which the molten silicon is cast;
Mounting a dummy bar of graphite material inside the one-way solidification unit;
Manufacturing a start block inside the one-way solidification part through melting of the silicon button on the dummy bar;
Feeding a silicon raw material in the form of particles into the silicon melting part and melting the silicon raw material fed by electron beam irradiation;
The molten silicon overflows while feeding the silicon raw material and melting of the fed silicon raw material continuously;
The molten silicon overflowed from the one-way solidification part is supplied, the molten silicon is transferred to the lower part by driving the start block downward while maintaining the molten state by electron beam irradiation, and then the lower part of the molten silicon is cooled to the upper direction. Refining through solidification; And
Cutting the upper portion of the refined silicon to remove metal impurities on the refined silicon; polysilicon manufacturing method comprising a.
The method of claim 7, wherein
Production of the start block
Injecting silicon chunks on the graphite dummy bars;
And melting-bonding the silicon chunk to the dummy bar by electron beam irradiation in a vacuum atmosphere.
The method of claim 7, wherein
The start block
Method for producing polysilicon, characterized in that descending at a rate of 0.005 ~ 0.05 mm / s.
The method of claim 7, wherein
The silicon raw material is
Polysilicon production method characterized in the form of particles of purity 2N, average particle diameter of 1 ~ 2mm.
The method of claim 7, wherein
And volatile impurities contained in the silicon raw material are evaporated under vacuum at the time of melting the silicon in the silicon melting part.
The method of claim 11,
In the process of solidifying the molten silicon, the metal impurity contained in the molten silicon is moved to the top along the solid-liquid interface, characterized in that the polysilicon manufacturing method.
Silicon for photovoltaic power generation which is cast by the method in any one of Claims 7-12, and has purity 5N-7N.

Images