JPH01115812A - Production device for silicon thin plate - Google Patents

Abstract

PURPOSE:To obtain a silicon thin plate of relatively large crystal grain without requiring cutting, by feeding molten silicon to a dented part of a rotary base and press molding. CONSTITUTION:Silicon fed to a melting crucible 13 of a feeder 12 is melted by a heater 15, gas pressure P is applied to the silicon, which is sent from a nozzle 13a of the crucible 13 to a dent 4 of a base 1. The step motor 10 is driven, the base 1 is subjected to step rotation at a given phase through an output gear 11, a driving gear 9 and a revolving shaft 3 and the dent 4 is stopped below a pressing jig 15. Then a rod 16a of an air cylinder 16 is extended, molten silicon in the dent 4 is pressed by the pressing jig 15 into a thin film and the base 1 is subjected to step rotation at given phase and stopped below a taking device 17. Then a rod part 19a of an air cylinder 19 is extended, a silicon thin plate in the dent 4 is adsorbed on the taking device, an air cylinder 22 is driven, the adsorbing device 17 is transferred to a mesh conveyor 24 and the silicon thin plate is dropped on a conveyor 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for manufacturing polycrystalline silicon thin plates used for solar cells, other photoelectric conversion elements, and the like.

[Prior Art] Generally speaking, there are three methods for manufacturing silicon thin plates used in solar cells and the like. First, the first manufacturing method is a casting method, in which molten silicon is unidirectionally solidified in a crucible, the solidified silicon blob is cut into square columns, and then further cut into thin plates.

This manufacturing method has the advantage that silicon thin plates of a desired size and thickness can be obtained, and is currently used as a manufacturing method for silicon thin plates (wafers) for solar cells. However, this method requires a large amount of cost to cut and also generates a large amount of cutting loss (cut margin) of high-purity silicon, so it is expensive and it is essentially impossible to significantly reduce costs. It was possible.

The second manufacturing method is a method in which a silicon ribbon is directly manufactured, and then a silicon thin plate having a desired size is manufactured by cutting. According to this method, cutting loss can be reduced compared to the first manufacturing method described above, so a significant cost reduction can be expected.

This method also includes an E F G (Edge-defining method) in which a silicon ribbon is pulled up from a slit
There is a method (ed-fIlm-fed-growrh),
The pulling speed was extremely slow at several tens of meters and seven minutes, resulting in an expensive method. Therefore, in order to significantly improve the production speed of silicon ribbon, we developed a method called HSW (Horixo
The n-tal 5upported Web) method is also under research and development, but the surface flatness of the silicon ribbon is poor, etc.
It has not yet been developed to a point where its characteristics are satisfactory.

Furthermore, the third manufacturing method is a spin method, in which molten silicon is poured into a rotating mold using centrifugal force. In this method, the bottom mold and the top lid are fixed, and molten silicon is poured into the space (cavity) between them using centrifugal force to directly form the desired size (for example, 10 cm x 10 cm,
A silicon thin plate with a thickness of 0.4 mm) was obtained. Although this method has the advantage of directly obtaining a thin silicon plate of the desired size, it also involves forming a mold in the cold, thinning the silicon at high temperature, and then lowering the temperature to dismantle the mold and take out the silicon thin plate. Since it is done like this, it is continuous,
Improvements were needed to save labor and reduce the energy required to preheat the mold.

[Problem to be Solved by the Invention 1] As described above, various methods of manufacturing silicon thin plates have advantages and disadvantages. That is, although the first manufacturing method has been put into practical use as a method for manufacturing polycrystalline silicon thin plates, there is a problem in that the manufacturing cost is high because a large amount of cutting loss occurs. In addition, in the second manufacturing method, a method that satisfies low cost and high quality has not been developed, and furthermore, the third manufacturing method
The manufacturing method had problems such as requiring improvements such as continuity and reduction of energy consumption.

[Means for Solving the Problems] The present invention provides a novel silicon thin plate manufacturing apparatus that solves the above-mentioned conventional problems.

The silicon thin plate manufacturing apparatus of the present invention includes a base having an upward facing board and rotatably installed around a vertical axis, and a recess for receiving molten silicon recessed in a non-axial position of the board of the base. a recess; a base rotation device that rotates the base in steps of a predetermined phase so that the recess is stopped at at least three different first, second, and third predetermined positions; and the first predetermined position. a device for supplying molten silicon into the recess, which is installed above a second predetermined position; a jig driving device for lowering the press jig for a predetermined period of time to press the silicon in the recess when the press jig is stopped at the third predetermined position; The device is further provided with a take-out device for taking out the thin silicon plate from within the recess.

[Function] In the present invention, since the thin silicon plate is press-molded within the recess of the desired size on the substrate, almost the entire amount of molten silicon is made into a thin plate. Therefore, there is no need for a cutting process such as the casting method, and there is no cutting loss (cutting margin) associated with cutting, making it possible to significantly reduce costs. In addition, since the thin plate manufacturing method uses pressing in a mold, the plate manufacturing speed is significantly faster than the EFG method, which involves pulling silicon thin strips through slits, and as a result, the number of equipment required per silicon thin plate is significantly increased. This makes it possible to reduce costs. In addition, compared to the spin method, there is no need to assemble or disassemble the mold, and press molding and removal are performed continuously at high temperatures, so unlike the spin method, the mold must be preheated from cold to high temperature each time. Therefore, there is no need to perform continuous molding with less energy consumption.

Furthermore, in the present invention, it is possible to preheat the substrate and press jig, and it is possible to control the cooling rate during solidification of molten silicon, so it is possible to produce thin silicon sheets with relatively large crystal grains, which have high light and electricity conversion efficiency. Obtainable.

[Example] Hereinafter, the present invention will be described in detail using examples shown in the drawings.

FIG. 1 is an overall configuration diagram showing one embodiment of a silicon thin plate manufacturing apparatus according to the present invention, FIG. 2 is a perspective view of the main parts of the same apparatus, and FIG. 3 is a partially cut-away enlarged front view of a substrate. The base 1 has an upwardly facing board surface 1a, and is attached to a rotating shaft 3 rotatably supported on the upper and lower surfaces 2a and 2b of the machine frame 2, as shown in FIG. Further, a plurality of recesses 4 for receiving molten silicon are provided at regular intervals in the circumferential direction at non-axial positions on the board surface 1a of the base 1, and a third recess 4 is provided near the recess 4. As shown in the figure, a heater 5 is provided so that the recess 4 can be heated. Note that the heater 5 is surrounded by a heat-resistant insulating material 6. Further, the heater 5 passes through the base 1 and the rotating shaft 3 together with a heat-resistant insulating material 6, and is electrically connected to a power supply ring 7 (see FIG. 1) attached to the outer periphery of the rotating shaft 3. The power supply ring 7 is the power supply ring 7.
Power is supplied from a power supply brush 8 that is in contact with the power supply brush 8 .

Furthermore, a drive gear 9 is fixed below the position of the power supply ring 7 on the rotating shaft 3, and the drive gear 9 is always in meshing engagement with the output gear 11 of the step motor 10.

The step motor 10 constitutes a base rotation device, and its drive rotates the base 1 in steps of a predetermined phase via an output gear 11, a drive gear 9, and a rotating shaft 3. As a result, the recesses 4 provided in the base 1 are stopped at three different first, second, and third predetermined positions.

Above the first predetermined position, as shown in FIG. 2, a supply device 12 for supplying molten silicon into the recess 4 is arranged. The supply device 12 is composed of a melting crucible 13 and a heater 14 disposed around the melting crucible 13. The silicon heated and melted in the melting crucible 13 is heated and melted by applying a gas pressure P to the melting crucible 13. The structure is such that a predetermined amount of molten silicon can flow down into the recess 4 from a nozzle 13a provided at the bottom of the melting crucible 13 at a predetermined time.

Further, above the second predetermined position, a press jig 15 for pressing the silicon accommodated in the recess 4 is arranged so as to be movable up and down. That is, the press jig 15 is
As shown in FIG. 1, the rod portion 16a of the air cylinder 16
The rod portion 16a is fixed to the lower end of the rod portion 16a, and can be moved up and down by the expansion and contraction movement of the rod portion 16a. Although it is not clear from the figure, a heater is incorporated inside the press jig 15, so that the press jig 15 can be heated. The air cylinder 16 constitutes a jig driving device, and is configured to be able to lower the press jig 15 for a predetermined time when the recess 4 is stopped at a predetermined position 342, thereby lowering the press jig 15. The silicon in the recess 4 is pressed using the jig 15.

Further, above the third predetermined position, a take-out device 17 is disposed for taking out the pressed silicon thin plate from inside the recess 4 when the recess 4 is stopped at the third predetermined position. There is. The extraction device 17 has a suction extraction structure and is connected to a vacuum device via a suction hose 18. Moreover, the take-out device 17 is an air cylinder 19.
It is fixed to the lower end of the rod part 19a, and has a structure that can be raised and lowered by the expansion and contraction movement of the rod part tea. Furthermore, a trolley 20 is provided at the upper end of the air cylinder 19.
is attached, and the air cylinder 19 is attached to the trolley 20.
It is now possible to horizontally move eight times on the guide rail 21 via the guide rail 21. Note that this guide rail 21 is fixed to the upper surface portion 2a of the machine frame 2. Said air cylinder 1
9, the tip of the rod portion 22a of the air cylinder 22 supported and fixed to the side surface 2c of the machine frame 2 is connected to a quick connection tool 23.
The air cylinder 19 and the extraction device 17 can be horizontally moved by the expansion and contraction of the rod portion 22a. Further, the silicon thin plate taken out from inside the recess 4 by the takeout device 17 is carried out to the outside by a mesh conveyor 24 for carrying out.

Note that the substrate 1 and the like are surrounded by a container (not shown) filled with an inert gas in order to prevent oxidation of the molten silicon.

Next, the operation of the silicon thin plate manufacturing apparatus will be described.

The silicon supplied into the melting crucible 13 of the supplying device 12 is heated and melted by the heater 14, and then the melting crucible 1 is heated by applying gas pressure P to the surface of the molten silicon.
A predetermined amount is supplied into the recess 4 of the base 1 from the nozzle 13a of No. 3. Note that, at this time, the board 1 is in a stopped state.

Next, the base 1 is rotated in a predetermined phase step, and the recess 4
is stopped below the press jig 15.

Thereafter, the rod portion 16a of the air cylinder 16 is extended, and the press jig 15 located at the lower end of the rod portion 16a presses the molten silicon in the recess 4 into a thin plate. Next, after the press jig 15 is raised, the base 1 is further rotated by a predetermined phase step, and the recess 4 is stopped below the extraction device 17. Thereafter, the rod portion 19a of the air cylinder 19 is extended, and the take-out device 17 located at its lower end is brought into contact with the solidified thin silicon plate in the recess 4, and the thin silicon plate is adsorbed. After that, the take-out device 17 is raised, and when it has risen to a predetermined position, the air cylinder 22
The take-out device 17 and the silicon thin plate are carried onto the mesh conveyor 24 for carrying out. Then, at this position, the extraction device 1
At the same time, the suction operation of the take-out device 17 is released, and the thin silicon plate is dropped onto the mesh conveyor 24 for carrying out, and is carried out to the outside.

In this way, the rotation of the base 1, the flow of the molten silicon, the pressing, and the removal of the thin plate are linked, so that the process from the flow of the molten silicon to the removal of the silicon thin plate can be performed automatically. In addition, 1. Since the substrate 1 is in a stopped state when supplying molten silicon, pressing, and taking out the thin plate, the operations of supplying, pressing, and taking out can be easily performed.

In addition, when cooling and solidifying molten silicon, the precipitated crystal grain size of polycrystalline silicon differs depending on the cooling rate, and the larger the cooling degree, the smaller the precipitated crystal grains become, and the less light is used as a solar cell.
Electrical conversion efficiency deteriorates.

In this embodiment, the recess 4 of the base 1 is supplied with molten silicon.
By keeping the temperature of the press jig 15 and the temperature of the press jig 15 at a high temperature of 1350° C. or higher, the cooling rate during pressing is reduced. The crystal grains of the resulting silicon thin plate were 1 mm.
The particle size was relatively large.

In the above-mentioned embodiment, a suction structure is used as the silicon thin plate extraction device 17, but the device is not limited to this, and the silicon thin plate in the recess 4 is pushed up from below. A structure in which it can be taken out from the recess 4 may also be used.

[Effects of the Invention] As explained above, according to the present invention, molten silicon is supplied into the recess of the base and a thin silicon plate is formed by pressing, so there is no need for cutting as in the casting method. Almost all of the molten silicon is made into a thin plate. Therefore, it is possible to significantly reduce costs compared to the casting method. Also, supplying molten silicon while rotating the base,
Continuous operation is easy because pressing and molded silicon thin plates are taken out. Furthermore, unlike the spin method, there is no need to preheat the mold from cold to high temperature each time, so energy consumption can be reduced.

In addition, since press molding is possible at high temperatures, the cooling rate during pressing is somewhat slow and relatively large crystal grains can be obtained, making it possible to produce silicon thin sheets for solar cells with high light-to-electrical conversion efficiency. It is possible.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing an embodiment of a silicon thin plate manufacturing apparatus according to the present invention, Fig. 2 is a perspective view of the main parts of the apparatus, and Fig. 3 is an enlarged front view with a part of the base cut away. . DESCRIPTION OF SYMBOLS 1... Base, 3... Rotating shaft, 4... Recessed part, 5... Heater, 10... Step motor, 12... Supply device, 14... Heater, 15...
...Press jig, 16-...Air cylinder, 17-
...Take-out device. Patent applicant: Nippon Sheet Glass Co., Ltd. Representative: Patent attorney Tsuyoshi Shigeno Figure 2

Claims (3)

[Claims] (1) A base having an upward facing board surface and rotatably installed around a vertical axis; a recess for receiving molten silicon formed in a non-axial position on the board surface of the base; and the recess is compatible with the base. at least three different first, second and third
a base rotation device that rotates the base in steps of a predetermined phase so that the base is stopped at a predetermined position; a supply device for supplying molten silicon into the recess, which is installed above the first predetermined position; A silicon press jig in the recess is installed above a second predetermined position so as to be freely raised and lowered, and when the recess is stopped at the second predetermined position, the press jig is lowered for a predetermined period of time. and a jig driving device for pressing the silicon in the recess, and a take-out device for taking out the thin silicon plate from the recess when the recess is stopped at the third predetermined position. Characteristic silicon thin plate manufacturing equipment. (2) The silicon thin plate manufacturing apparatus according to claim 1, further comprising a heater for preheating the recessed portion. (3) The silicon thin plate manufacturing apparatus according to claim 1 or 2, comprising a heater for preheating the press jig.