JP4273659B2 - 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 and the heaters 52 and 53 to give a positive temperature gradient in the molten metal 54 from the bottom to the top of the mold 51, and gradually cools the molten metal 54 from the bottom.・ Grow crystals upward by 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]
At this time, in order to generate an ingot having good unidirectional solidification, it is ideal that all the heat removal from the mold 51 is performed from the bottom surface side and not from the side wall surface 51a side. Therefore, a heat insulating material 56 is provided around the cooling plate 55 outside the side wall surface 51 a of the mold 51.
Here, when the silicon raw material S is accommodated in the mold 51, even if the top of the silicon raw material S is piled up as much as possible beyond the side wall 51a, the silicon raw material S is chip-shaped solid silicon. Therefore, when melted, the liquid level of the molten metal 54 did not reach the upper end of the side wall 51a of the mold 51.
[0005]
[Problems to be solved by the invention]
However, in the conventional crystalline silicon manufacturing apparatus 50 that employs the above-described unidirectional solidification method, there is a demand for increasing the amount of polycrystalline silicon ingots manufactured at one time without increasing the size of the crystalline silicon manufacturing apparatus 50. For this reason, there has been a demand for supplying the silicon raw material S so that the liquid level of the molten metal 54 exists up to the vicinity of the upper end of the side wall 51a of the mold 51.
Further, even when the silicon raw material S is supplied to the mold 51 at the same time, there is a demand for maintaining an argon gas atmosphere when the silicon raw material S is heated and melted.
[0006]
The present invention has been made in view of the above circumstances, and intends to achieve the following object.
(1) To increase the amount of silicon material to be supplied at one time without increasing the size of the mold.
(2) To increase the number of polycrystalline silicon ingots that can be manufactured at one time.
[0007]
[Means for Solving the Problems]
In the crystalline silicon manufacturing apparatus of the present invention, a mold for containing a molten metal obtained by melting a silicon raw material in a chamber, a chill plate on which the mold is placed, and an endothermic plate provided below the chill plate, An upper heating part and a lower heating part that are disposed above and below the mold and that heat the silicon raw material to generate the molten metal, and are provided above the mold to increase the amount of the molten metal before heating. And an increase plate having an inclined surface toward the inside of the mold so that the silicon material placed with heating falls into the mold, and the increase plate has a side wall of the mold. Is provided on a heat insulating material disposed around the part, and after the upper heating part and the lower heating part are operated to generate the molten metal, the upper heating part is operated and the lower heating part is operated. Operation Absorbs heat by seals to the heat absorbing plate, the coagulation of the molten metal in the mold is initiated, by stopping the operation of the subsequent over heating unit, thereby gradually solidified toward the top of the molten metal in said mold from the bottom The above problem was solved.
In the present invention, it is desirable that the increase plate is provided with a fall prevention plate for preventing the silicon raw material from dropping in addition to the mold.
In the present invention, it is also possible to adopt a means in which a pair of the increasing plates are provided so as to face each other with the mold interposed therebetween.
[0008]
In the crystalline silicon manufacturing apparatus of the present invention, on the upper side of the mold, a silicon raw material is placed before heating, and an inclined surface which faces the mold so that the silicon raw material placed with heating falls into the mold Is provided on the silicon raw material increase plate in an amount that cannot be accommodated only by the mold before heating, and is heated to be accommodated in the mold as a molten metal. Therefore, the amount of molten metal can be increased. As a result, the polycrystalline silicon ingot can be enlarged without increasing the size of the mold.
At this time, by providing the increasing plate on the upper side of the mold, the silicon raw material on the increasing plate can be shortened to the heating means provided on the upper side of the mold as compared with the silicon raw material inside the mold. It is possible to heat the silicon material on the expansion plate more rapidly than the melting of the silicon material inside the mold. Here, the increase plate is not limited to a plate shape as long as it has the inclined surface.
[0009]
In the present invention, on the inclined surface of the increasing plate, a silicon plate placed other than the mold is provided on the end side in the direction away from the mold by providing a fall prevention plate protruding above the inclined surface. The raw material can be prevented from falling. At the same time, it is possible to further increase the amount of silicon raw material that can be placed on the weight increase plate by the fall prevention plate. Here, the fall prevention plate should just protrude above the said inclined surface, and is not limited to plate shape.
[0010]
In the present invention, by providing a pair of the increasing plates so as to face each other with the mold interposed therebetween, it becomes possible to supply a larger amount of silicon raw material than when the increasing plate is provided only on one side of the mold. . Thereby, it is possible to further increase the amount of molten metal accommodated in the mold, and it is possible to further increase the size of the polycrystalline silicon ingot without increasing the size of the mold.
[0011]
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 a crystalline silicon manufacturing apparatus according to the present embodiment. FIG. 2 is an enlarged view showing the vicinity of the weight increasing plate of FIG. 1. In FIG. is there.
[0012]
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 that surrounds the container 5, and a surrounding furnace 6 that surrounds the chill plate 8. An upper heating unit 7a and a lower heating unit 7b for generating silicon melt (molten metal) 3 by heating silicon (silicon raw materials) 3a and 3b and a pair of increasing plates 9 and 9 are provided.
[0013]
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. .
[0014]
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 is piped through the top plate portion of the surrounding furnace 6 through the top plate portion. The inflow nozzle allows 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 installed outside the chamber 2. .
[0015]
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.
On the chill plate 8, the container 5 is placed 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 side wall part 5 a is provided so as to surround the periphery of the side wall part of the crucible 4, and the upper end thereof is set to be at least a position higher than the liquid level of the silicon melt 3. The bottom 5 b is in close contact with the bottom of the chill plate 8 and the crucible 4.
[0016]
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.
[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]
As shown in FIGS. 1 and 2, a pair of increasing plates 9 and 9 are provided on the upper side of the side wall 4 b of the crucible 4 at positions facing each other with the crucible 4 interposed therebetween. On each of the increasing plates 9 made of carbon, an inclined surface that faces the inside of the crucible 4 so that the solid silicon 3b is placed before heating and the solid silicon 3b placed along with the heating falls into the crucible 4. 9a is provided. Further, a drop prevention plate 9b that protrudes upward from the inclined surface 9a is provided on the end portion side in the direction away from the crucible 4 on the inclined surface 9a of the increasing plate 9, that is, on the upper end side of the inclined surface 9a. . The tip portions of the inclined surfaces 9a, 9a on the crucible 4 side are both located inside the crucible 4 in plan view.
[0019]
In the pair of increasing plates 9, 9, the distance between the tip portions on the crucible 4 side of the opposed inclined surfaces 9 a, 9 a is set smaller than the distance between the side wall parts 4 b, 4 b of the opposed crucible 4. The interval between the fall prevention plates 9b, 9b is set larger than the interval between the side wall portions 4b, 4b of the opposing crucible 4.
These increasing plates 9 and 9 are provided on the heat insulating materials 10 and 10 around the side wall 4b of the crucible 4. In addition, the heat insulating material 10 is abbreviate | omitted in FIG.
[0020]
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. The surrounding furnace 6 is provided with a view port for observation, a temperature sensor, a port through which wirings of the heating means 7a and 7b are passed, and the like.
[0021]
When crystal silicon is manufactured using the crystal silicon manufacturing apparatus 1 having the above-described configuration, first, raw material chip-shaped solid silicon 3a is accommodated in the crucible 4, and then the raw material chip-shaped solid silicon 3b. Is placed on the weight increase plates 9 and 9.
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 temperature of the solid silicon 3a in the crucible 4 is raised and melted to produce a silicon melt 3 ', the volume of the solid silicon 3a is reduced compared to that of the solid silicon 3a, and the increase plate 9 heated by the upper heating unit 7a is heated. The solid silicon 3 b falls along the inclined surface 9 a and is accommodated in the crucible 4. At the same time, the silicon melt 3 is generated by melting the solid silicon 3b in the crucible 4 when the melting temperature is reached. The melting temperature of silicon is 1480 ° C. The silicon melts 3 and 3 ′ are generated at the same time.
[0022]
When the silicon melt 3 is generated, the operation of the lower heating unit 7b is stopped while the upper heating unit 7a is kept in an operating state, and when the shutter is opened, the heat in the surrounding furnace 6 is absorbed from the lower opening to the heat absorbing plate 13 Endothermic. Thereby, the inside of the surrounding furnace 6 falls 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.
[0023]
In this embodiment, the solid silicon 3b produced on the basis of only the solid silicon 3a accommodated in the crucible 4 is melted, and the solid silicon 3b on the expansion plate 9 is also melted to raise the liquid level. A silicon melt 3 can be generated. For example, in the case of a crystalline silicon manufacturing apparatus capable of producing 100 kg of silicon melt 3 ′ without the increase plates 9, 150 kg of silicon melt 3 can be generated by providing the increase plates 9, 9. It has become possible. Thereby, the polycrystalline silicon ingot produced | generated without performing the enlargement of the crucible 4 which requires the enlargement of the whole silicon manufacturing apparatus 1 can be enlarged.
At this time, by providing the increasing plate 9 on the upper side of the crucible 4, the upper heating part 7 a provided on the upper side of the crucible 4 from the solid silicon 3 b on the increasing plate 9 as compared with the solid silicon 3 a inside the crucible 4. And the solid silicon 3b on the expansion plate 9 can be heated more quickly than the solid silicon 3a inside the crucible 4. For this reason, heating time can be shortened.
[0024]
At this time, the fall prevention plate 9b is provided at the upper end portion of the inclined surface 9a of the increasing plate 9, so that the solid silicon 3b can be prevented from falling outside the crucible 4. At the same time, it is possible to further increase the silicon raw material that can be placed on the weight increase plate 9 by the fall prevention plate 9b. The fall prevention plate 9b may have other structures as long as it prevents the solid silicon 3b from dropping other than the crucible 4, such as a structure integrated with the main body of the weight increasing plate 9 so that the inclined surface 9a rises gently. Is also possible.
[0025]
Further, since the pair of increasing plates 9 are provided on both sides of the crucible 4 as shown in FIG. 1, as compared with the case where the increasing plate 9 is provided only on one side of the crucible 4 as shown in FIG. In addition, the solid silicon 3c can be placed up to a height defined by the pair of fall prevention plates 9b, 9b, and more solid silicon 3c can be supplied to the crucible 4.
[0026]
【The invention's effect】
The crystalline silicon manufacturing apparatus of the present invention has the following effects.
(1) On the upper side of the mold, there is provided an increasing plate having an inclined surface directed into the mold so that the silicon material is placed before heating and the silicon material placed with heating falls into the mold. Therefore, not only the inside of the mold but also the silicon raw material increasing plate in an amount that cannot be accommodated only by the mold before heating, and this can be heated and accommodated in the mold as a molten metal. Can be increased. As a result, the polycrystalline silicon ingot can be enlarged without increasing the size of the mold.
(2) A silicon raw material placed other than the mold is provided on the inclined surface of the increasing plate by providing a fall prevention plate protruding above the inclined surface on the end side in the direction away from the mold. Can be prevented from falling. At the same time, this drop prevention plate can further increase the silicon raw material that can be placed on the weight increase plate.
(3) By providing a pair of the increase plates so as to face each other with the mold interposed therebetween, it becomes possible to supply a larger amount of silicon raw material than when the increase plate is provided only on one side of the mold. Thereby, it is possible to further increase the amount of molten metal accommodated in the mold, and it is possible to further increase the size of the polycrystalline silicon ingot without increasing the size of the mold.
[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 cross-sectional view showing the vicinity of an increase plate in 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, 3b ... Solid silicon (silicon raw material)
4 ... Crucible (mold)
5 ... Container 5a ... Side wall 6 ... Surrounding furnace 8 ... Chill plate 9 ... Increase plate 9a ... Inclined surface 9b ... Fall prevention plate

Claims (3)

In the chamber, a mold for containing a molten material obtained by melting silicon raw material, a chill plate on which the mold is placed, a heat absorption plate provided at a lower position of the chill plate, and an upper position and a lower position of the mold. An upper heating unit and a lower heating unit that are arranged to heat the silicon raw material to generate the molten metal, and are provided on the upper side of the mold to increase the amount of the molten metal. with in the and a bulking plate placed silicon raw material has an inclined surface toward the inside mold to fall into the mold, the bulking plate, heat insulating material arranged around the side wall of the mold It is provided on the
After the upper heating unit and the lower heating unit are operated to generate the molten metal, the operation of the lower heating unit is stopped while the upper heating unit is operated to absorb heat by the heat absorbing plate, and the molten metal in the mold An apparatus for producing crystalline silicon , characterized in that solidification of the molten metal in the mold is gradually solidified from the lower part to the upper part by starting solidification of the upper part and then stopping the operation of the upper heating unit . 2. The crystal silicon manufacturing apparatus according to claim 1, wherein the expansion plate is provided with a fall prevention plate for preventing the silicon raw material from dropping in addition to the mold. 3. The crystalline silicon manufacturing apparatus according to claim 1, wherein a pair of the increase plates are provided so as to face each other with the mold interposed therebetween.

Images