JP4258974B2 - 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, for example, in an argon gas atmosphere, as shown in FIG. 3, the silicon raw material S is accommodated in a mold 51 formed in a substantially rectangular parallelepiped shape, and this is performed by an upper heater 52 and a lower heater 53 that are separated from the mold 51. It is generated by melting the silicon raw material S to form a molten metal 54, then releasing the heating by the lower heater 53 and extracting the mold 51 from the bottom surface side by the cooling plate 55 to solidify it. The ingot generated at this time adjusts the cooling plate 55, the heaters 52 and 53, and the heat insulating material 56 to give a positive temperature gradient from the bottom of the mold 51 to the upper side in the molten metal 54, so that the molten metal 54 is at the bottom. The crystal grows upwards by gradually cooling and solidifying. 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]
In the crystal silicon manufacturing apparatus 50, the mold 51 is installed in the surrounding furnace 57 provided in the chamber. In the surrounding furnace 57, wiring of the heater 52, an observation view port, a temperature sensor, and the like are provided. , A plurality of through holes 58 are provided therethrough.
[0005]
[Problems to be solved by the invention]
By the way, in the above-mentioned unidirectional solidification method, when silicon is heated and melted, the temperature is considerably high (1000 ° C. or higher), and the silicon and the carbon material which is a main component in the furnace generate inert gas. The SiC reacts at a high temperature to generate SiC gas. This SiC gas has a problem that, when the silicon melt is rapidly cooled, it grows into SiC crystals and adheres to the inside and outside of the furnace. In addition to this, the deposits adhering to the inside and outside of the surrounding furnace 57 had to be cleaned.
Here, when the surrounding furnace 57 and the inside of the chamber outside thereof communicate with each other through a plurality of through holes 58, 58, as shown by arrows in FIG. It is considered that the gas enters and returns to the outside of the surrounding furnace 57 by entering the outside of the surrounding furnace 57 through 58 and returning to the inside of the surrounding furnace 57 from another through hole 58.
[0006]
The present invention has been made in view of the above circumstances, and intends to achieve the object of reducing deposits inside the chamber outside the surrounding furnace.
[0007]
[Means for Solving the Problems]
In the crystalline silicon production apparatus of the present invention, a mold for containing molten metal, an enclosing furnace for enclosing the mold, heating means for heating the silicon raw material accommodated in the mold to generate a molten metal, and an enclosure In the crystalline silicon manufacturing apparatus having a plurality of through holes penetrating the furnace, the space inside the chamber outside the surrounding furnace is separated by providing a partition, and only one through hole communicates with the separated space. The above problem was solved by setting as follows. In the present invention, it is possible to the partition wall to adopt means comprising disposed in surrounding furnace side.
[0008]
In the crystalline silicon manufacturing apparatus of the present invention, the space inside the chamber outside the surrounding furnace is separated by providing a partition, and only one through hole is set to communicate with the separated space. Since the through holes do not communicate with each other due to the partition walls, it is possible to reduce the entry of gas that may generate deposits from the inside of the surrounding furnace into the chamber outside the surrounding furnace . Further, the term “separation” does not necessarily mean sealing, but means that the inside of the chamber outside the enclosure furnace is divided so that at least the gas that generates deposits does not enter from the through hole.
[0009]
Further, in the present invention, the partition wall is arranged on the surrounding furnace side, so that even during heating, the space inside the chamber outside the surrounding furnace is kept separated as described above, and the deformation due to heat is performed. Etc. can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a crystalline silicon manufacturing apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a front sectional view showing an embodiment of the crystalline silicon manufacturing apparatus in the present embodiment, and FIG. 2 is an enlarged front sectional view (a) and a plan view (b) showing the vicinity of the partition wall in FIG. Reference numeral 1 denotes a crystal silicon manufacturing apparatus.
[0011]
As shown in FIG. 1, the crystalline silicon manufacturing apparatus 1 has a crucible (mold) 4 for containing a silicon melt 3, a container 5 for containing the crucible 4, and a crucible 4 accommodated in a chamber 2. A chill plate 8 on which the container 5 is placed, a crucible 4, a container 5, a surrounding furnace 6 that surrounds the chill plate 8, and an upper position and a lower position of the crucible 4 in the surrounding furnace 6. An upper heating section 7a and a lower heating means 7b for generating silicon melt (molten metal) 3 by heating silicon (silicon raw material) 3a are provided.
[0012]
A hollow portion 2a is formed inside the wall constituting the chamber 2, and the cooling of the chamber 2 after melting the solid silicon 3a and the inside thereof can be efficiently performed by flowing cooling water therethrough. .
[0013]
The surrounding furnace 6 has a top plate portion, a bottom plate portion, and side plate portions surrounding the periphery of the top plate portion, the bottom plate portion, and the periphery thereof, and is formed in a cylindrical shape as shown in FIG. It has a square shape. A support portion 64 is provided opposite to the lower portion of the surrounding furnace 6, and the container 5 is supported on the support portion 64 via the chill plate 8.
An inflow nozzle 20 is piped through the top plate portion of the surrounding furnace 6 through the top plate portion. The inflow nozzle 20 allows argon gas, which is an inert gas, to flow into the surrounding furnace 6 and is installed outside the chamber 2 so that the distance to the silicon melt 3 can be changed by driving the elevating mechanism 20a. ing.
[0014]
The upper heating unit 7 a is composed of 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. These upper heating part 7a and lower heating part 7b form a heating means.
The container 5 is placed on the chill plate 8 in close contact with the chill plate 8. The container 5 made of carbon has a bowl shape having a side wall portion 5a and a bottom portion 5b, and the crucible 4 is accommodated therein. The container 5 can be omitted.
[0015]
A heat absorbing plate 13 is provided below the chill plate 8 of the surrounding furnace 6. The heat absorbing plate 13 is for absorbing the radiant heat in the surrounding furnace 6 when the silicon melt 3 is cooled, and is attached to a position facing the chill plate 8 in the lower part of the chamber 2 and is made of carbon. . A lower opening is formed in the surrounding furnace 6 at a position below the mounting table 5, and a shutter that can be opened and closed is provided in the lower opening. In this shutter, the lower opening is closed when the solid silicon 3a is heated, and the shutter is opened when the silicon melt 3 is cooled.
[0016]
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.
[0017]
Furthermore, an upper opening is provided in the upper part of the side plate portion of the surrounding furnace 6, and an upper opening / closing mechanism for opening and closing the upper opening is also provided. The upper opening / closing mechanism includes an opening / closing door and an actuator connected to the opening / closing door. When the solid silicon 3a is heated, the opening / closing door is in a state of closing the upper opening, and when the silicon melt 3 is cooled, the opening / closing door is opened by driving the actuator. 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 the lower cooling nozzle 21 or the like when the silicon melt 3 is cooled.
[0018]
A plurality of through holes 23, 24, and 25 are provided in the top plate portion of the surrounding furnace 6, and as shown in FIGS. 1 and 2, the through hole 23 is an observation viewport, and the through hole 24 is a temperature. The sensor port and the through hole 25 are ports through which the wirings of the upper and lower heating parts 7a and 7b pass.
A partition wall 30 is provided so as to separate the inside of the chamber 2 outside the surrounding furnace 6 corresponding to each through hole 23, 24, 25 with respect to the plurality of through holes 23, 24, 25 penetrating the surrounding furnace 6. Yes. These partition walls 30 are disposed in the surrounding furnace 6, and the inside of the chamber 2 outside the surrounding furnace 6 is separated corresponding to the through holes 23, 24, 25 so that the through holes 23, 24, 25 do not communicate with each other. It is arranged like this.
In the figure, the front end of the partition wall 30 and the inside of the chamber 2 are spaced apart from each other, but this is an interval at which the gas inside the surrounding furnace 6 does not enter from the through holes 23, 24, 25. It is also possible to have 30 tips connected to the inside of the chamber 2 to completely separate the parts.
[0019]
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.
Next, the shutter and the upper opening / closing door are closed, and argon gas flows into the surrounding furnace 6 from the inflow port 20 to maintain a gas atmosphere at a predetermined pressure, and in this state, the upper heating unit 7a and the lower heating unit 7b are operated. The temperature in the surrounding furnace 6 is increased.
Then, the solid silicon 3a in the crucible 4 is melted by the lower heating part 7b and the upper heating part 7a. When the melting temperature is reached, the silicon melt 3 is generated. The melting temperature of silicon is 1480 ° C.
[0020]
When the silicon melt 3 is generated, the operation of the lower heating unit 7b is stopped while the upper heating unit 7a remains in an operating state, and when the shutter is opened, heat is conducted from the crucible 4 to the chill plate 8 to be cooled. At the same time, the heat absorbing plate 13 directly absorbs heat from the penetrating portion 8b of the chill plate 8 as indicated by an arrow in FIG.
At the same time, the heat in the surrounding furnace 6 is absorbed by the heat absorbing plate 13 from the lower opening. As a result, the inside of the surrounding furnace 6 is lowered from the melting temperature of silicon to about 1000 ° C. 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 and the operation of the upper heating unit 7a is also stopped, the silicon melt 3 in the crucible 4 is gradually solidified from the lower part to the upper part.
As described above, by applying a positive temperature gradient from the bottom of the crucible 4 to the upper side and cooling the silicon melt 3, silicon is solidified and crystallized.
[0021]
In this embodiment, since the partition wall 30 is provided in the chamber 2 outside the surrounding furnace 6 and the through holes 23, 24, 25 are not in communication with each other, the gas inside the surrounding furnace 6 is not heated during heating and cooling. Can be prevented from entering the through-holes 23, 24, and 25, thereby preventing gas that generates deposits from entering the chamber 2 outside the surrounding furnace 6. Therefore, it is possible to greatly reduce the adhesion of deposits in the chamber 2 outside the surrounding furnace 6. As a result, there is no need to clean the outside of the surrounding furnace 6.
[0022]
In addition, a through-hole can be considered other than said structure, and also in this case, the partition 30 can be provided corresponding to each through-hole.
[0023]
【The invention's effect】
According to the crystalline silicon manufacturing apparatus of the present invention, the space inside the chamber outside the surrounding furnace is separated by providing a partition wall, and only one through hole communicates with the separated space . It is possible to prevent the through holes from communicating with each other by this partition wall, and to reduce the entry of gas that may generate deposits from the inside of the surrounding furnace into the chamber outside the surrounding furnace. As a result, there is an effect that it is possible to greatly reduce adhesion of deposits in the chamber outside the surrounding furnace.
[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.
2 is an enlarged front sectional view (a) and a plan view (b) showing the vicinity of a partition wall of the crystalline silicon manufacturing apparatus of FIG. 1. FIG.
FIG. 3 is a schematic view showing a conventional crystalline silicon manufacturing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Crystal silicon production apparatus 2 ... Chamber 3 ... Silicon melt (molten metal)
3a: Solid silicon (silicon raw material)
4 ... Crucible (mold)
5 ... Container 6 ... Enclosing furnace 8 ... Chill plates 23, 24, 25 ... Through hole 30 ... Partition

Claims (2)

The chamber has a mold for containing the molten metal, an enclosing furnace for enclosing the mold, heating means for heating the silicon raw material accommodated in the mold to generate the molten metal, and a plurality of through holes penetrating the enclosing furnace. In the crystalline silicon manufacturing apparatus, the space inside the chamber outside the surrounding furnace is separated by providing a partition, and the crystal is characterized in that only one through hole communicates with the separated space. Silicon manufacturing equipment.   2. The crystalline silicon manufacturing apparatus according to claim 1, wherein the partition wall is disposed on the surrounding furnace side.

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