JP2000302431A - Device and method for producing platy silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for producing a platy silicon and a method for producing the platy silicon, enabling the effective and stable production of the platy silicon. SOLUTION: This device 1 for producing the platy silicon is provided with a melted silicon-receiving tank 2 which has a heater 4 and is used for receiving melted silicon L-Si, and with a coagulation tank 3 which is disposed at a place adjacent to the melted silicon-receiving tank 2 and receives a melted metal S comprising melted tin. The melted metal S is convected using heaters 8, 9, 10 which are set at different temperatures, respectively. The melted silicon L-Si is laterally pulled out from a space portion 12 with contact with the bath surface of the melted metal S and then cooled and coagulated into the platy silicon S-Si. Since the lower surface of the pulled melted silicon L-Si is supported on the melted metal S, the formation of the thin platy silicon S-Si can stably be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate silicon manufacturing apparatus and a plate silicon manufacturing method.

[0002]

2. Description of the Related Art For example, a Si crystal used for a solar cell or a semiconductor wafer is formed by forming an ingot in which a crystal is oriented in one direction by a Czochralski method or a casting method, and cutting (slicing) the ingot. Is done. However, such a so-called batch method is a discontinuous method and has a large number of steps, so that the working efficiency is low, and a cutting margin is required at the time of slicing an ingot, so that the material use efficiency is low. On the other hand, as shown in FIG. 2, the cooling gas CG is locally supplied from the cooler 51 to the bath surface of the molten silicon L-Si stored in the storage tank 50 by being supplied from the supply unit 53. The method of forming the plate-like silicon S-Si by solidifying the bath surface portion and pulling out the solidified ribbon-like silicon in the horizontal direction is effective because the process is continuous and the work efficiency is good. Also, since a slicing step such as a batch type is not required, material use efficiency is high.

[0003]

However, in the method shown in FIG. 2, the spraying of the cooling gas CG may cause the silicon surface to become unstable, such as waving, Since the portion H is a free end, it is difficult to stably pull out the sheet-like silicon S-Si when it is desired to reduce the thickness. On the other hand, as shown in FIG. 3, plate silicon S-Si is formed on the surface of the substrate 60 by bringing the molten silicon L-Si guided to the gutter 61 into contact with a ceramic or carbon substrate 60 moving in the lateral direction. There is a way to
In such a method, due to a difference in thermal expansion between the molten silicon L-Si and the substrate 60, a solidification expansion of the molten silicon L-Si, and the like, the defect density inside the formed plate-like silicon S-Si increases. There is a problem.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a plate silicon manufacturing apparatus and a plate silicon manufacturing method capable of efficiently and stably forming plate silicon. Aim.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an invention according to claim 1 is provided with a molten silicon storage tank having heating means for storing molten silicon, and a molten silicon storage tank adjacent to the molten silicon storage tank. A solidification tank containing a molten metal having a temperature lower than the solidification temperature of the molten silicon; anddrawing means for drawing out the molten silicon in a lateral direction while removing heat while contacting the molten silicon with a molten metal bath surface of the solidification tank. I do. According to the present invention, the plate silicon is continuously obtained by drawing the molten silicon to the surface of the molten metal bath of the coagulation tank and removing and solidifying the heat, so that the working efficiency is increased. Further, since the conventional slicing process is not required, the material use efficiency is improved. Further, since the lower surface of the drawn molten silicon is supported by the molten metal and the drawn portion is not a free end, flat and thin plate-like silicon is stably formed. At this time, since the heat of the molten silicon is removed only from the lower surface side, the plate-like silicon crystal to be formed is oriented in one direction.

According to a second aspect of the present invention, there is provided the apparatus for producing plate-like silicon according to the first aspect, wherein the molten metal is made of a molten metal having a lower melting point than the silicon. According to the present invention, the use of the molten metal having a lower melting point than the silicon as the molten metal allows the heat removal of the molten silicon to be performed stably.

According to a third aspect of the present invention, there is provided the apparatus for producing plate-like silicon according to the first or second aspect, wherein the molten metal is molten tin or a tin alloy. According to the present invention, by using tin or a tin alloy as a molten metal, without reacting with molten silicon,
The heat removal of the molten silicon can be performed stably. Even if Sn is contained as a trace impurity in a product, a high-quality product can be manufactured without affecting its characteristics.

According to a fourth aspect of the present invention, there is provided the apparatus for producing plate-like silicon according to any one of the first to third aspects, wherein a wall surface of the molten silicon storage tank adjacent to the solidification tank is provided. The gap from which the molten silicon is drawn out is formed below the bath surface of the molten silicon. According to the present invention, since the molten silicon is drawn from below the bath surface, stable drawing can be realized without being affected by the waving of the bath surface.

According to a fifth aspect of the present invention, there is provided the plate-like silicon manufacturing apparatus according to any one of the first to fourth aspects, wherein the inside of the molten silicon storage tank is drawn out adjacent to the solidification tank. And a receiving tank to which molten silicon is supplied from the outside. The drawing tank and the receiving tank communicate with each other below the partition. According to the present invention, the portion to which the molten silicon is supplied and the portion to be extracted are separated by the partition portion, so that the waving of the bath surface generated when the molten silicon is supplied does not propagate to the draw-out tank, so that the molten silicon Is stable.

According to a sixth aspect of the present invention, there is provided the apparatus for producing plate-like silicon according to any one of the first to fifth aspects, wherein the solidification tank has a temperature gradient reduced in a direction in which the silicon is drawn. Means is provided. According to the present invention, the molten metal in the solidification tank is always maintained in a molten state by the heating means and has a temperature gradient, so that convection occurs. Therefore, since the heat exchange on the surface of the molten metal in contact with the silicon is always performed, the solidification of the silicon is performed under certain conditions. Therefore, continuous formation of plate-like silicon is performed stably.

According to a seventh aspect of the present invention, plate-like silicon is drawn by drawing molten silicon contained in a molten silicon storage tank in a lateral direction while contacting the molten silicon with a molten metal bath having a temperature lower than the solidification temperature of the molten silicon. It is characterized by forming. According to the present invention, since the drawn portion is no longer a free end as in the related art, the thinning and flattening of the plate-like silicon can be stably performed, and the plate-like silicon can be continuously formed. Further, since the heat of the molten silicon is removed only from the lower surface side, the plate-like silicon can obtain crystals oriented in one direction.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing a manufacturing apparatus of a silicon plate according to an embodiment of the present invention; FIG. 1 is a side sectional view for explaining a configuration of a plate-like silicon manufacturing apparatus 1 of the present invention. FIG.
In the manufacturing apparatus 1, a molten silicon storage tank 2 in which molten silicon L-Si is stored, and a molten silicon storage tank 2
And a coagulation tank 3 in which the molten metal S is stored.

A heater 4 as a heating means and a heat insulating material 14 are provided on the wall of the molten silicon storage tank 2. The heater 4 is for maintaining the molten state of the molten silicon L-Si supplied from a molten silicon supply unit (not shown).
Only Si is kept at about 1400 degrees.

The interior of the molten silicon storage tank 2 is adjacent to a receiving tank 6 for receiving the molten silicon L-Si supplied from the molten silicon supply unit and a coagulation tank 3 by a partition 5 formed in a plate shape. And a drawer tank 7. The lower part of the partition 5 is arranged so as to be separated from the bottom surface of the molten silicon storage tank 2, and the receiving tank 6 and the drawer tank 7 communicate with each other below the partition 5.

The portion of the wall surface of the draw-out tank 7 of the molten silicon storage tank 2 adjacent to the solidification tank 3 has a molten silicon L
A gap portion 12 formed below the -Si bath surface is provided. The gap 12 is formed so as to extend in the horizontal direction at a position substantially at the same height as the bath surface of the molten metal S, and the molten silicon L-Si is drawn out from the gap 12. The interval between the gaps 12 is adjusted so as to correspond to the thickness of the plate-like silicon to be formed, and has an interval of, for example, about 200 μm.

The molten metal S set to a temperature lower than the solidification temperature of the molten silicon L-Si is accommodated in a solidification tank 3 provided adjacent to the molten silicon storage tank 2. As the molten metal S, it is preferable to use a molten metal having a melting point lower than the silicon melting point. Further, it is preferable to use a molten metal having a boiling point higher than the silicon melting point and a higher specific gravity than silicon. Specifically, it is preferable to use a molten metal having a melting point of 1000 degrees or less and a boiling point of 2000 degrees or more. It is also necessary to have a property of not reacting with silicon and not forming silicide. Further, it is necessary that the influence of the product characteristics is small even when the impurities are mixed in the wafer. From such a viewpoint, it is preferable to use molten tin or a tin alloy as the molten metal S.

The coagulation tank 3 includes first, second, and third heaters 8 as heating means provided in a plurality in the drawing direction y.
9 and 10 are provided. The first, second, and third heaters 8, 9, and 10 are provided at the bottom of the solidification tank 3, and adjust the temperature of the molten metal S made of tin or a tin alloy to adjust the molten state of the molten metal S. It is for maintaining. The molten metal S is heated to about 300 to 1 by these heaters.
It is maintained at a temperature of 400 degrees. At this time, the temperature difference between the molten metal S and the molten silicon L-Si is large,
The heat insulating material 14 prevents mutual heat exchange.

The first, second, and third heaters 8, 9, 1
0 is set to different temperatures. In this case, the heater arranged on the upstream side is set to have the highest temperature, and the set temperature is gradually lowered toward the downstream side. That is, the first heater 8 is set to the highest temperature, and the temperature is set to become lower as the temperature of the second and third heaters 9 and 10 becomes higher.
Therefore, the temperature gradient of the molten metal S in the coagulation tank 3 decreases in the silicon extraction direction y. At this time,
Convection occurs inside the molten metal S by each heater set at different temperatures.

Downstream of the coagulation tank 3, there is provided a drawer 13 for drawing silicon solidified by coming into contact with the bath surface of the molten metal S in the lateral direction (drawing direction y). That is, the plate-shaped silicon S-Si obtained by solidifying the molten silicon L-Si is drawn out to the downstream side by the drawing-out means 13. Downstream of the coagulation tank 3, a gas blowing unit 11 for blowing gas onto the back surface of the drawn plate-shaped silicon S-Si to blow off molten metal adhered is provided diagonally.

The molten silicon storage tank 2 and the partition 5
The solidification tank 3 is formed of quartz or carbon. Further, the entire manufacturing apparatus 1 is provided under an inert gas (such as argon) or a hydrogen atmosphere, and the surface of the molten silicon L-Si bath, the surface of the molten S bath, or the surface of the plate-like silicon S-Si is inert gas. Covered with.

The operation in the case where plate silicon is manufactured using the manufacturing apparatus 1 having such a configuration will be described.
First, molten silicon L-S is supplied from a molten silicon supply unit (not shown) to the receiving tank 6 of the molten silicon storage tank 2.
i is continuously supplied. Supplied molten silicon L-
Si passes through the communicating portion below the partition 5 and draws out the tank 7.
The molten silicon storage tank 2 is supplied with molten silicon L
-Si filled. At this time, molten silicon L-Si
Is supplied until the bath surface is located above the gap 12. The molten silicon L-Si filled in the molten silicon storage tank 2 maintains a stable molten state by the heating of the heater 4.

In the gap 12 of the molten silicon storage tank 2,
A molten silicon L-Si is placed in advance so that molten silicon L-Si can be drawn out, and the molten silicon storage tank 2 is filled with the molten silicon L-Si.
2 in the horizontal direction (drawing direction y). At this time, the size of the space between the gaps 12 is plate-like silicon S-Si.
Is adjusted based on the target value of the thickness. For example, the target value of the thickness of the plate-like silicon to be formed is 200 μm
In this case, the interval between the gaps 12 is set to be 200 μm or slightly larger. That is, since the size of the gap portion 12 and the drawing speed contribute to the thickness of the formed plate-shaped silicon S-Si, the plate-shaped silicon S-Si having a desired thickness can be obtained by adjusting these. . At this time, depending on conditions such as the pull-out speed, the pulled-out silicon may be thinner as a whole, but this can be coped with by providing the space of the gap 12 slightly larger than the target value.

The molten silicon L-Si drawn out of the gap 12 comes in contact with the bath surface of the molten metal S set at a temperature lower than the solidification temperature of the silicon, so that the molten silicon L-Si moves in one direction (thickness direction) from the lower surface side. Heat is removed. Then, as the molten silicon L-Si is drawn to the downstream side, the heat is further removed and gradually solidified while forming a solidification interface H. At this time, the solidification interface H is a starting point of solidification.

When the plate-like silicon S-Si to be formed is used for a solar cell or the like, it is necessary to orient the crystal in one direction and solidify it. When it is desired to grow a crystal in the thickness direction of the plate-like silicon S-Si, it is desirable that the solidification interface H, which is the starting point of solidification, be as horizontal as possible. At this time, by forming the solidification interface H broadly, the solidification interface H becomes closer to the horizontal, so that plate-like silicon S-Si having good unidirectional solidification can be obtained, and the growth rate increases.

The molten metal S has a temperature gradient that decreases in the drawing direction y by the heaters 8, 9, and 10, and convection is generated accordingly. That is, while the heat removal temperature of the molten silicon L-Si is adjusted,
The temperature distribution of the molten metal S is always controlled. Further, the bath surface of the molten metal S in contact with the silicon being drawn is
The heat exchange is always performed by the convection of, and a constant state is always maintained. At the same time, the temperature of the inert gas covering the entire manufacturing apparatus 1 is also adjusted, and the surface of the plate-like silicon is controlled to be stable.

The molten silicon L-Si drawn to the bath surface of the molten metal S in which the temperature on the upstream side in the drawing direction y is high and the temperature on the downstream side is low is gradually solidified as it moves to the downstream side. As a result, a plate-like silicon S-Si as a solid is obtained.

The formed plate-like silicon S-Si is drawn out downstream by the drawing-out means 13. Coagulation tank 3
The gas blowing part 11 is provided on the back side of the plate-like silicon drawn out to the downstream side (that is, the side which has been in contact with the molten metal S).
Gas is blown from. With this gas, the molten metal attached to and taken out from the back surface of the plate-shaped silicon S-Si is removed. Then, the plate-like silicon S-Si drawn further downstream is cut into a predetermined size by a cutter or the like, and is conveyed to the next step.

As described above, the plate-like silicon S-Si is supplied from the molten silicon L-Si contained in the molten silicon storage tank 2.
Can be continuously formed by drawing laterally while contacting the bath surface of the molten metal S set at a temperature lower than the solidification temperature of the molten silicon L-Si. And
Since the conventional slicing step is not required, the margin for cutting can be suppressed and the material use efficiency can be increased.

The lower surface of the drawn molten silicon L-Si is configured to be supported by the molten metal S. That is, since the drawn portion is no longer a free end, thin and flat plate-shaped silicon can be stably formed.
Further, since the heat of the molten silicon L-Si is removed only from the lower surface side, the crystal of the plate-like silicon S-Si to be formed is oriented in one direction. Therefore, for example, a plate-like silicon S-Si having a desired performance can be formed for a solar cell. Also, unlike the method of solidifying silicon on the ceramic substrate surface,
Since the molten silicon L-Si is supported by the liquid molten metal S made of molten tin or molten tin alloy, there is no influence of heat shrinkage during silicon solidification and cooling. That is, in the case of tin, the solidification temperature is 232 degrees, but up to this temperature, no stress is generated due to the difference in thermal expansion.

The molten metal S has a temperature gradient lowered in the drawing direction y by the heaters 8, 9 and 10, and convection is generated accordingly. That is, the heat removal temperature of the molten silicon L-Si by the molten metal S is adjusted, and the control of the temperature distribution of the molten metal S is always performed. Therefore, the molten silicon L-Si is solidified stably as it is drawn to the downstream side. Further, since the heat exchange of the bath surface of the molten metal S in contact with the silicon is always performed by the convection of the molten metal S, the state of formation of the solidification interface H, the formation position on the molten metal S bath surface, or the molten silicon L−
The heat removal temperature and the like of Si are always stable. Also,
By using tin or tin alloy as the molten metal S,
The molten silicon L-Si is stably extracted without reacting with the molten metal S and without affecting the characteristics of the product. At the same time, since the temperature of the inert gas surrounding the entire manufacturing apparatus 1 is adjusted, the surface of the plate-like silicon is also formed stably. Then, by such a method, plate-shaped silicon S-Si having a thickness of, for example, 100 to 400 μm can be formed.

The molten silicon L-Si is a molten silicon L-Si.
Since the molten silicon is drawn out from the gap 12 formed below the bath surface, it is stably drawn out without being affected by the waving of the molten silicon storage tank 2. That is, when the drawing is performed directly from the molten silicon L-Si bath surface, it is difficult to form thin plate-like silicon S-Si when the bath surface is wavy due to, for example, the influence of atmospheric gas. By drawing the molten silicon L-Si from below the bath surface, the influence of the bath surface is reduced even if the bath surface is wavy.

Further, since the inside of the molten silicon storage tank 2 is partitioned into the receiving tank 6 and the draw-out tank 7 by the partitioning portion 5, the waving generated when the molten silicon L-Si is supplied to the receiving tank 6 is reduced. Therefore, the light does not propagate to the gap 12 formed in the drawer tank 7 as the drawer portion. Therefore, stable extraction can be performed while enabling continuous supply of the molten silicon L-Si, so that the plate-shaped silicon S-Si can be continuously and stably formed.

By the way, it is also possible to provide a changing means for changing the size of the space between the gaps 12.
That is, for example, the gap upper member 12a shown in FIG. 1 is supported by the support portion so as to be able to move up and down, and an actuator such as a servo-motor is attached to the support portion so that the size of the gap portion 12 can be changed. Although the thickness of the plate-like silicon S-Si contributes to the size of the gap between the gaps 12 and the drawing speed, the thickness of the plate-like silicon S-Si formed by providing a changing means for changing the gap between the gaps 12 is provided. -The thickness of -Si can be changed variously, and it can respond quickly to various specifications.

The apparatus 1 for manufacturing plate-like silicon having such a configuration can be used not only for manufacturing a solar cell but also for manufacturing a semiconductor wafer.

[0035]

The apparatus and method for manufacturing plate silicon according to the present invention have the following effects. (1) According to the first aspect of the present invention, the plate-like silicon is continuously obtained by drawing the molten silicon to the surface of the molten metal bath of the coagulation tank and removing and solidifying the molten silicon, so that the working efficiency is increased. Further, since the conventional slicing process is not required, the material use efficiency is improved. Further, since the lower surface of the drawn molten silicon is supported by the molten metal and the drawn portion is not a free end, flat and thin plate-like silicon is stably formed. At this time, since the heat of the molten silicon is removed only from the lower surface side, the plate-like silicon crystal to be formed is oriented in one direction. (2) According to the invention described in claim 2, by using a molten metal having a lower melting point than the silicon as the molten metal,
The heat removal of the molten silicon is performed stably. (3) According to the third aspect of the invention, by using tin or a tin alloy as the molten metal, the heat of the molten silicon can be stably removed without affecting the characteristics of the product silicon wafer. be able to. (4) According to the fourth aspect of the invention, since the molten silicon is drawn from below the bath surface, stable drawing can be realized without being affected by the waving of the bath surface. (5) According to the fifth aspect of the invention, since the portion to which the molten silicon is supplied and the portion to be pulled out are separated by the partition portion, the waving of the bath surface generated when the molten silicon is supplied is drawn out. Since it does not propagate to the tank, the molten silicon is drawn out stably. (6) According to the sixth aspect of the invention, the molten metal in the solidification tank is always maintained in a molten state by the heating means and has a temperature gradient, so that convection occurs. Therefore, since the heat exchange on the surface of the molten metal in contact with the silicon is always performed, the solidification of the silicon is performed under certain conditions. Therefore, continuous formation of plate-like silicon is performed stably. (7) According to the invention as set forth in claim 7, the drawn portion is no longer a free end as in the prior art, so that the thinning and flattening of the plate-like silicon are performed stably and the continuous formation of the plate-like silicon is continued. Formation is possible. Further, since the heat of the molten silicon is removed only from the lower surface side, the plate-like silicon can obtain crystals oriented in one direction.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing one embodiment of a plate-like silicon manufacturing apparatus of the present invention.

FIG. 2 is a diagram illustrating a conventional plate silicon manufacturing apparatus.

FIG. 3 is a view illustrating a conventional plate silicon manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plate-shaped silicon manufacturing apparatus 2 Molten silicon storage tank 3 Solidification tank 4 Heater (heating means) 5 Partition part 6 Receiving tank 7 Drawer tank 8 First heater (heating means) 9 Second heater (heating means) 10 Third heater ( Heating means) 12 Gap 13 Pull-out means 14 Insulating material L-Si molten silicon S-Si plate silicon S molten metal (molten tin or molten tin alloy)

Continued on the front page (72) Inventor Yuji Ishiwari 1-297 Kitabukuro-cho, Omiya-shi, Saitama F-term in Mitsubishi Materials Research Laboratory 4G072 AA01 BB02 GG03 GG04 HH01 MM08 MM38 NN30 UU01 UU02 5F053 AA50 BB60 DD01 FF05GG02 LL04 LL05 RR05 RR06 RR13

Claims (7)

[Claims] A molten silicon storage tank provided with heating means for storing molten silicon; a solidification tank adjacent to the molten silicon storage tank and containing a molten metal having a temperature lower than the solidification temperature of the molten silicon; And a drawing means for drawing out in a lateral direction while removing heat while making contact with the molten metal bath surface of the coagulation tank. 2. The apparatus according to claim 1, wherein the molten metal is made of a molten metal having a lower melting point than the silicon. 3. The apparatus for producing plate-shaped silicon according to claim 1, wherein said molten metal is molten tin or tin alloy. 4. The apparatus for producing plate-like silicon according to claim 1, wherein a gap portion from which molten silicon is drawn out is formed on a wall surface of said molten silicon storage tank adjacent to said solidification tank. Is formed below the bath surface of molten silicon. 5. The apparatus for producing plate-like silicon according to claim 1, wherein molten silicon is supplied from the outside of the molten silicon storage tank to a drawing tank adjacent to the solidification tank and from the outside. And a receiving tank connected to the drawer tank, wherein the drawer tank and the receiving tank communicate with each other below the partition. 6. The apparatus for producing plate-like silicon according to claim 1, wherein the solidification tank includes a heating unit having a temperature gradient that decreases in a direction in which the silicon is drawn. Characteristic plate silicon manufacturing equipment. 7. A plate-like silicon is formed by drawing out molten silicon contained in a molten silicon storage tank in a lateral direction while contacting the molten silicon bath surface at a temperature lower than the solidification temperature of the molten silicon. A method for producing plate-like silicon.