JP4444482B2 - Crystalline silicon production equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a crystalline silicon manufacturing apparatus that cools and gradually solidifies a silicon melt in one direction.
[0002]
[Prior art]
Polycrystalline silicon solar cells are the most commonly produced solar cells today. The most important performance of a power generation element (solar cell) of a polycrystalline silicon solar cell is energy conversion efficiency. This energy conversion efficiency greatly depends on the crystal grain boundaries of the substrate and the crystal orientation in the crystal grains. These are for reducing the energy conversion efficiency due to the shortening of the life of the carrier in the solar cell and the decrease of the mobility. Therefore, in order to improve the energy conversion efficiency, in the manufacture of polycrystalline silicon, the crystal grain boundary is reduced as much as possible, in other words, the crystal grain size is grown as large as possible, and It is important to improve the orientation.
[0003]
A typical method for producing polycrystalline silicon is a unidirectional solidification method. In this method, the chamber in which the crucible is arranged is filled with an inert gas such as argon gas, and the solid silicon of the raw material contained in the crucible is heated by heating means arranged above and below the crucible to form a silicon melt, Next, while stopping the operation of the heating means below the crucible, the inert gas is blown to the bottom of the crucible, and a positive temperature gradient is applied in the silicon melt upward from the bottom of the crucible. Then, the silicon melt is gradually cooled and solidified from the bottom to grow the crystal upward. According to this method, it is known that a polycrystalline silicon ingot having a crystal grain size of several millimeters or more sufficient as a solar cell wafer can be obtained.
[0004]
[Problems to be solved by the invention]
However, although the conventional technology adopting the above-mentioned unidirectional solidification method cools the silicon melt by performing control by a heating means and heat absorption by circulation of an inert gas such as argon gas at the time of cooling, Cooling alone has a limit in solidifying the silicon melt, and there is a problem that it takes a long time for cooling.
[0005]
In view of the above circumstances, an object of the present invention is to provide a crystalline silicon manufacturing apparatus capable of further shortening the cooling time of a silicon melt.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention employs the following means.
In the present invention, the crucible for storing the silicon melt in the chamber, the mounting table for mounting the crucible, the surrounding furnace for surrounding the crucible and the mounting table, and the upper and lower positions of the crucible in the surrounding furnace. A lower opening / closing mechanism configured to open and close a lower opening formed in a bottom portion of an enclosing furnace, in each of the crystalline silicon manufacturing apparatuses, each of which is disposed and generates a silicon melt by heating solid silicon, and a lower heating unit; the heat in the surrounding furnace through the lower opening have a heat absorbing plate for absorbing heat, the heat absorbing plate, together with the chamber, characterized in that it forms a cooling water passage for cooling water circulating in the chamber.
[0007]
Thus, by having the lower opening / closing mechanism that opens and closes the lower opening of the surrounding furnace, and the heat absorbing plate arranged below the lower opening / closing mechanism, the heat absorbing plate reduces the heat in the surrounding furnace when the lower opening is opened. Since heat is absorbed through the opening, the cooling efficiency in the surrounding furnace is increased, and the cooling time can be surely shortened. In addition, the endothermic plate, together with the chamber, forms a cooling water passage for the cooling water flowing through the chamber, and the cooling water promotes the endothermic action of the endothermic plate by cooling the endothermic plate. Can be kept good.
[0008]
In this invention of Claim 2, the said lower heating part is arrange | positioned at intervals so that the position facing the lower opening of the said surrounding furnace may be avoided, and it is a cooling effect, without inhibiting the heat absorption by a heat sink. Can be increased.
[0010]
According to a third aspect of the present invention, there is provided an upper opening / closing mechanism for opening / closing an upper opening formed in a side plate portion of the surrounding furnace.
Due to the opening operation by the upper opening / closing mechanism, heat is also radiated from the upper side in the surrounding furnace, so that the cooling time is further shortened.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIGS. 1 and 2, the crystalline silicon manufacturing apparatus 1 includes a crucible 4 that contains a silicon melt 3 in a chamber 2, a mounting table 5 on which the crucible 4 is mounted, a crucible 4 and a mounting table. An enclosing furnace 6 that surrounds 5, and an upper heating section 7 a and a lower heating section 7 b that are respectively disposed above and below the crucible 4 within the enclosing furnace 6 and that heat the solid silicon 3 a to generate the silicon melt 3. And are provided.
[0012]
A hollow portion 2a is formed inside the wall constituting the chamber 2, and cooling water is allowed to flow therethrough to efficiently cool the chamber 2 after melting the solid silicon 3a and the inside thereof. . The mounting table 5 mounts the crucible 4 via a heat insulating material 5a.
[0013]
As shown in FIG. 2, the surrounding furnace 6 has a top plate portion 61, a bottom plate portion 62, and a side plate portion 63 surrounding the periphery of the top plate portion 61, a bottom plate portion 62, and a side plate portion 63 surrounding them. As shown in FIG. 2, it has a cylindrical shape as shown in FIG. A support portion 64 is provided opposite to the lower part of the surrounding furnace 6, and the mounting table 5 is supported on the support portion 64 via the chill plate 8.
An inflow nozzle 20 is piped through the top plate 61 in the top plate 61 of the surrounding furnace 6. The inflow nozzle 20 allows an argon gas, which is an inert gas, to flow into the surrounding furnace 6, and the distance to the silicon melt 3 can be changed by driving an elevating mechanism 20 a installed outside the chamber 2. ing.
[0014]
The upper heating unit 7 a and the lower heating unit 7 b are constituted by a plurality of heaters arranged along the length direction of the crucible 4. Further, the lower heating part 7 b is located below the chill plate 8 and is disposed between the support parts 64 of the surrounding furnace 6.
[0015]
The surrounding furnace 6 has a lower opening 9 formed at a position below the mounting table 5 and a lower opening / closing mechanism 10 for opening and closing the lower opening 9. The lower opening / closing mechanism 10 includes a shutter 11 that opens and closes the lower opening 9 and an actuator 12 that opens the shutter 11 in a direction away from each other along the bottom surface of the bottom plate portion 62 of the surrounding furnace 6. As shown in FIG. 1, the shutter 11 closes the lower opening 9 by driving the actuator 12 as shown in FIG. 1, and when the silicon melt 3 is cooled, the actuator 12 is driven as shown in FIG. The shutter 11 is opened. The shutter 11 is also made of carbon so as to perform a heat insulating function.
[0016]
An endothermic plate 13 is provided at a position below the shutter 11 of the surrounding furnace 6. The heat absorbing plate 13 is for absorbing the radiant heat in the surrounding furnace 6, and is attached to a position facing the lower opening 9 and the shutter 11 in the lower part of the chamber 2 and is made of carbon.
[0017]
Further, the heat absorbing plate 13 forms a cooling water passage 14 for cooling water flowing through the chamber 2. That is, the endothermic plate 13 is arranged with an appropriate space with the bottom surface of the chamber 2, and the cooling water channel 14 is formed in the chamber 2 by the space between the hollow portion 2 a in the chamber 2 and the bottom surface of the chamber 2 and the endothermic plate 13. It is formed so as to surround the whole.
A cooling nozzle 21 that penetrates the chamber 2 and the heat absorbing plate 13 is provided at the bottom of the chamber 2. The cooling nozzle 21 flows into the surrounding furnace 6 from below so that argon gas is blown toward the chill plate 8 when the silicon melt 3 is cooled.
[0018]
Further, as shown in FIG. 2, the surrounding furnace 6 has an upper opening 15 provided on the upper side of the side plate portion 63, and also has an upper opening / closing mechanism 16 that opens and closes the upper opening 15. The upper opening / closing mechanism 16 includes an opening / closing door 17 attached to the outer surface of the side plate portion 63 via a hinge so as to be opened and closed, and an actuator 18 connected to the opening / closing door 17 via a pivot joint 19. When the solid silicon 3a is heated, the open / close door 17 keeps the upper opening 15 of the side plate portion 63 closed as shown by the solid line in FIG. 2, and when the silicon melt 3 is cooled, the actuator 18 is driven to open and close the door. The door 17 is opened as shown by the chain line.
[0019]
Furthermore, an exhaust port 22 is piped on the upper part of the surrounding furnace 6 and the chamber 2. This exhaust port 22 is for exhausting the argon gas when it flows into the surrounding furnace 6 from below when the silicon melt 3 is cooled.
In FIG. 1, 23 is a view port for observation, 24 is a temperature sensor, and 25 is a port through which wirings of the upper and lower heating units 7a and 7b are passed.
[0020]
When crystal silicon is manufactured using the crystal silicon manufacturing apparatus 1 having the above-described configuration, first, raw material chip-shaped solid silicon 3 a is accommodated in the crucible 4. At this time, the shutter 11 of the lower opening / closing mechanism 10 closes the lower opening 9 as shown in FIG. 1, and the opening / closing door 17 of the upper opening 16 closes the opening 15 of the surrounding furnace 6.
Next, argon gas is flowed into the surrounding furnace 6 from the inflow port 20 and maintained in a gas atmosphere at a predetermined pressure. In this state, the upper heating section 7a and the lower heating section 7b are operated to raise the temperature in the surrounding furnace 6; When the melting temperature is reached, the solid silicon 3a in the crucible 4 is melted, whereby the silicon melt 3 is generated. Incidentally, the melting temperature of silicon is 1480 ° C.
When the silicon solution 3 is generated, the silicon solution 3 is cooled, so that silicon is solidified and crystallized.
[0021]
At the time of the cooling, in order to solidify the silicon solution 3 in the crucible 4 in one direction from the lower part to the upper part, the upper heating part 7a is kept in an operating state, and the lower heating part 7b is stopped, and then the lower opening / closing mechanism 10 When 11 is opened as shown in FIG. 3, the heat in the surrounding furnace 6 is absorbed by the heat absorbing plate 13 from the lower opening 9. Thereby, the inside of the surrounding furnace 6 falls from the melting temperature of silicon to about 1000 ° C.
[0022]
Further, at the time of cooling, the cooling water flows through the hollow portion 2 a of the chamber 2, so that the heat in the surrounding furnace 6 is transferred from the heat absorbing plate 13 to the cooling water in the chamber 2.
In this case, argon gas flows in from the lower side by the cooling nozzle 21 to cool the chill plate 8 side, while the argon gas in the surrounding furnace is exhausted from the exhaust port 22, so that the heat in the surrounding furnace 6 is changed to argon gas. It discharges with it.
[0023]
Then, when the lower part in the surrounding furnace 6 falls to 1000 ° C. or lower, the silicon melt 3 in the crucible 4 starts to solidify. When the silicon melt 3 starts to solidify, the operation of the upper heating unit 7a is also stopped, so that the silicon melt 3 in the crucible 4 is gradually solidified from the lower part to the upper part.
Further, the opening / closing door 17 of the upper opening / closing mechanism 16 is opened, and the heat in the surrounding furnace 6 is also dissipated from the upper opening 15 into the space between the chamber 2 and the surrounding furnace 6 so that the entire inside of the surrounding furnace 6 is argon. Cooled by endothermic gas.
[0024]
In this embodiment, it has a lower opening / closing mechanism 10 that opens and closes the lower opening 9 of the surrounding furnace 6, and a heat absorption plate 13 disposed below the shutter 11 of the lower opening / closing mechanism 10, and when the shutter 11 is opened, the heat absorption plate 2 absorbs the heat in the surrounding furnace 6 through the lower opening 9, so that the cooling efficiency in the surrounding furnace 6 is increased and the cooling time can be shortened reliably.
[0025]
In addition, the endothermic plate 13 forms a cooling water passage 14 together with the lower wall of the chamber 2, and the cooling water promotes the endothermic action of the endothermic plate 13 by cooling the endothermic plate 13, so that the endothermic action of the endothermic plate 13 is improved. Can keep.
[0026]
In addition, not only the lower opening / closing mechanism 10 but also the upper opening / closing mechanism 16 is provided in the surrounding furnace 6, and the upper side in the surrounding furnace 6 absorbs heat, so that the cooling time can be further shortened. In addition, argon gas is allowed to flow into the surrounding furnace 6 from the lower opening 9 by the cooling nozzle 21 and the heat in the upper part of the surrounding furnace 6 is exhausted from the exhaust port 22, so that further shortening can be achieved. .
[0027]
Furthermore, since the lower heating part 7b is spaced apart from each other so as to avoid the position facing the lower opening 9, the lower heating part 7b does not impede the endothermic action by the heat absorbing plate 13, and the cooling effect Can be increased.
[0028]
【The invention's effect】
As described above, according to the first aspect of the present invention, the lower opening / closing mechanism that opens and closes the lower opening of the surrounding furnace, and the heat absorbing plate disposed below the lower opening, when the lower opening is opened, Since the heat absorbing plate absorbs the heat in the surrounding furnace through the lower opening, the cooling efficiency in the surrounding furnace is increased, and there is an effect that the cooling time can be surely shortened. Moreover, since the cooling water promotes the endothermic action of the endothermic plate by cooling the endothermic plate, the endothermic action of the endothermic plate can be kept good.
[0029]
According to the second aspect of the present invention, when the lower heating parts are arranged at intervals, the cooling effect can be enhanced also by this.
[0031]
According to the third aspect of the present invention, by an opening operation by the upper opening and closing mechanism, the upper portion of the surrounding furnace is also sucked heat, increasing shortening of cooling time further.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing an embodiment of an apparatus for producing crystalline silicon according to the present invention.
FIG. 2 is a side sectional view of the crystalline silicon manufacturing apparatus of FIG.
FIG. 3 is an enlarged front sectional view of a main part showing a state in which a lower opening is opened by a lower opening / closing mechanism.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crystalline silicon manufacturing apparatus 2 Chamber 3 Silicon melt 4 Crucible 5 Mounting stand 6 Surrounding furnace 9 Lower opening 10 Lower opening / closing mechanism 11 Shutter 12 Actuator 13 Endothermic plate 16 Upper opening / closing mechanism 17 Opening / closing door 18 Actuator

Claims (3)

In the chamber, a crucible for storing the silicon melt, a mounting table for mounting the crucible, a surrounding furnace for surrounding the crucible and the mounting table, and an upper position and a lower position of the crucible in the surrounding furnace, In a crystalline silicon manufacturing apparatus having a lower heating unit and heating a solid silicon to produce a silicon melt,
A lower closing mechanism for opening and closing the lower opening formed in the bottom of the surrounding furnace, and a heat absorption plate absorbs heat in the surrounding furnace through the lower opening possess,
The heat absorbing plate forms a cooling water channel for cooling water flowing through the chamber together with the chamber.   2. The crystalline silicon manufacturing apparatus according to claim 1, wherein the lower heating unit is disposed at an interval so as to avoid a position facing the lower opening of the surrounding furnace. Crystalline silicon manufacturing apparatus according to claim 1 or 2, characterized in that it has an upper opening and closing mechanism for opening and closing the upper opening formed in the side plate portion of the surrounding furnace.

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