JP3512576B2 - Silicon casting equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon casting apparatus, and more particularly, to a silicon casting apparatus for supplying a silicon raw material into a mold, heating and melting the raw material, and then unidirectionally solidifying it to form an ingot.

[0002]

2. Description of the Related Art A conventional silicon casting apparatus is shown in FIG.
In FIG. 3, 11 is a mold made of graphite or the like,
Reference numeral 12 is a cooling plate, 13 is a resistance heater, and 14 is a heat insulating wall made of graphite or the like. In this silicon casting apparatus, a mold release material containing silicon nitride or silicon carbide as a main component is applied to the inner wall surface of the mold 11, a silicon raw material 17 is supplied into the mold 11, and the silicon raw material 17 is supplied to the heater 1.
3 to 1500 ° C. to melt and melt, and then gradually lower the mold 11 to gradually separate the silicon melt 17 from the heater 13 and cool it, or lower the temperature of the heater 13 with the position of the mold 11 unchanged. It is cooled and the silicon melt is unidirectionally solidified in the mold 11 to form an ingot (for example, US Pat. No. 3,898,051, 5th Internationa).
l PVSEC p303-305). The ingot of the unidirectionally solidified silicon melt 17 is taken out from the mold 11 by breaking the mold 11, or in the case of an assembled mold, the mold 11 is disassembled and taken out.

[0003]

However, the bulk specific gravity of the silicon raw material 17 used in such a method for casting silicon is usually 1.0 to 1.5, which is only about half the specific gravity of silicon which is 2.33. . Therefore, in the conventional silicon casting apparatus shown in FIG. 3, the height of the ingot 17 formed by solidifying the silicon melt is only about half that of the mold 11. The mold 11 and a mold release material (not shown) applied to the inner wall surface of the mold 11 are expensive consumables and occupy a large proportion of the running cost. Therefore, in the prior art, since the ingot 17 that can be formed is small, but the required mold 11 is large, there is a problem that the cost of the mold 11 and the mold release material per weight of the ingot 17 becomes high.

The present invention has been invented in view of the above problems of the conventional apparatus, and provides a silicon casting apparatus in which the cost of the mold and the mold releasing material per weight of the ingot is increased. The purpose is to do.

[0005]

In order to achieve the above object, in the silicon casting apparatus according to the present invention, a heater for heating and melting the silicon raw material in the mold is provided around the mold, and the heater and the mold are provided. In a silicon casting apparatus covered with a heat insulation wall, a movable door is provided above the heat insulation wall, a plurality of raw material supply tanks are provided on the movable door, and a silicon raw material can be supplied from the raw material supply tank into the mold. I chose

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of a silicon casting apparatus according to the present invention, 1 is a mold made of graphite or the like, 2 is a cooling plate in which a coolant such as water circulates, 3 is a resistance heater, Reference numeral 4 is a heat insulating wall made of graphite or the like, and 5a and 5b are raw material supply tanks provided above the heat insulating wall. Such mold 1 and heat insulation wall 4
Etc. are all installed in a vacuum container (not shown).

In the present invention, raw material supply tanks 5a and 5b made of stainless steel or the like are provided above the mold 1. The raw material supply tanks 5a and 5b are also installed in the vacuum container together with the mold 1. An opening 4a is provided above the heat insulating material 4, and a funnel 6 made of stainless steel or the like for dropping the silicon raw material is provided on the opening 4a. The raw material supply tanks 5a and 5b are installed on the funnel 6. A silicon material dropping port 5c is provided below the raw material supply tanks 5a and 5b, and a lid 5d is provided below the dropping port 5c. When the silicon raw material is additionally supplied to the mold 1, the lid 5d is opened and the silicon raw material in the raw material supply tanks 5a and 5b is dropped into the mold 1 through the funnel 6. The plate of the lid 5d rotates about the hinge 5e so that the lid 5d becomes horizontal in the closed state. That is, for example, a rotary shaft (not shown) is extended to the outside of the vacuum container, and this rotary shaft is directly rotated outside the vacuum container to open / close the lid 5d.

Further, as shown in FIG. 2, the size of the lid 5d is made somewhat larger than the inner size of the drop opening 5c. Lid 5d
In this way, the silicon raw material 8 does not spill down from the lid 5d even if there is a slight gap between the outlet 5c and the lid 5d. In the case of a silicon raw material, since each α in FIG. 2 is about 30 °, it is advisable to make the lid 5d larger than the inner dimension of the drop opening 5c by 3 times or more the spacing on one side. That is, the space X and the lid 5d below the raw material supply tanks 5a and 5b.
The overhanging dimension Y of is Y ≧ 3X. Further, by providing a space between the outlet 5c and the lid 5d, the lid 5d can be stably opened and closed, and the silicon raw material 8 can be stably supplied. A movable door 4b is provided between the funnel 6 and the opening 4a of the heat insulating wall 4 as shown in FIG. 1, and the movable door 4b is provided outside the vacuum container only when the silicon raw material 8 is dropped. Thermal efficiency is good if you use an air cylinder to shift it sideways.

The casting method when two raw material supply tanks 5a and 5b are provided is as follows. First, the silicon raw material 8 previously supplied into the mold 1 is heated by the heater 3 to be melted. Next, when the silicon raw material 8 is melted and a space is formed above the mold 1, the silicon raw material 8 in the first raw material supply tank 5a is supplied into the mold 1. Next, when the additionally supplied silicon raw material 8 is melted and an empty space is formed above the mold 1, the silicon raw material 8 in the second raw material supply tank 5b is supplied into the mold 1. Finally, when all the silicon raw materials 8 are melted, the output of the heater 3 is reduced to unidirectionally solidify.

When casting silicon, the amount of melt when all the silicon raw materials 8 are melted is set to 90% of the effective depth of the mold 1. Then, since the solid of silicon has a bulk that is about 10% larger than that of the melt of silicon, the height of the finished ingot 7 becomes the same as the effective depth of the mold 1. Since the bulk of the additionally supplied silicon raw material 8 is also reduced when melted, it is difficult to use the entire effective depth of the mold 1 with one raw material supply tank 5a, 5b. If the number of raw material supply tanks is increased, the entire effective depth of the mold 1 can be used, but the production cost of the apparatus increases. Therefore, it is suitable that the number of raw material supply tanks is 3 to 5.

[0011]

As described above, according to the silicon casting apparatus of the present invention, the heater for heating and melting the silicon raw material in the mold is provided around the mold, and the heater and the mold are covered with the heat insulating wall. In the silicon casting apparatus, a movable door is provided above the heat insulating wall, and a plurality of raw material supply tanks are provided on the movable door so that the silicon raw material can be supplied from the raw material supply tank into the mold. Since silicon can be cast by effectively utilizing the depth of the mold,
The cost of the mold and mold release material per weight of the ingot is reduced. When casting in a mold of the same height, the weight of the ingot is about twice that of the conventional method. Further, since the method of additionally supplying the silicon raw material is simple, the cost is low and the reliability is high. It is possible to additionally supply from a fine silicon raw material having a diameter of about 0.1 mm to a large silicon raw material having a diameter of about 100 mm with the same apparatus.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a silicon casting apparatus according to the present invention.

FIG. 2 is a view showing a raw material supply tank section of the silicon casting apparatus according to the present invention.

FIG. 3 is a diagram showing a conventional silicon casting apparatus.

[Explanation of symbols]

1 ... Mold, 2 ... Cooling plate, 3 ... Heater, 4 ...
..Insulation walls, 5 ... Raw material supply tanks

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Claims (2)

(57) [Claims] 1. In a silicon casting apparatus in which a heater for heating and melting the silicon raw material in the mold is provided around the mold, and the heater and the mold are covered with a heat insulating wall, a movable door is provided above the heat insulating wall, A plurality of raw material supply tanks are provided on the movable door, and a silicon raw material can be supplied into the mold from the raw material supply tanks. 2. A lid is provided at a lower portion of the raw material supply tank at an interval, and a dimension of the lid protruding from the raw material supply tank is three times or more the interval.
The silicon casting apparatus described in 1.