JP3426793B2 - Method and apparatus for manufacturing polycrystalline semiconductor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a polycrystalline semiconductor by melting and solidifying a semiconductor material into a polycrystalline semiconductor.

[0002]

2. Description of the Related Art As a method for producing a polycrystalline semiconductor, for example, as disclosed in JP-A-62-167213, raw material silicon is melted in a crucible, and the molten silicon is cooled and solidified to obtain polycrystalline silicon. It is known how to do it.

FIG. 5 is an explanatory view for each step for explaining the conventional manufacturing process of polycrystalline silicon.

First, as shown in FIG. 5 (a), the raw material silicon 2 is put into the crucible 1 and heated by a heater (not shown) to melt the raw material silicon 2, and the molten silicon 3 is melted as shown in FIG. 5 (b). And

Next, the heating of the crucible 1 is stopped and the molten silicon 3 is cooled. The molten silicon 3 is solidified when its temperature becomes equal to or lower than the melting point temperature (1415 ° C.), and becomes polycrystalline silicon 6 as shown in FIG.

After that, the polycrystalline silicon 6 is pulled up as shown in FIG.

However, according to this conventional method, as shown in FIG.
There is a problem that it takes a long time to cool the molten silicon 3 in the step (c) by natural cooling.

Therefore, in order to shorten the time required for this cooling, an apparatus shown in FIG. 6 has been proposed. In this conventional device, a cooling device 8 for circulating cooling water 9 is provided below the crucible 1. The cooling device 8 has a movable portion so as to be vertically movable.

At the time of cooling, the heat conduction is improved by reducing the distance d between the cooling device 8 and the crucible 1, and the molten silicon 3 is cooled efficiently. In addition, when heating the raw material silicon, the crucible 1 having a large distance d is used.
Is insulated from the cooling device 8.

A manufacturing apparatus having the structure shown in FIG. 7 has also been proposed. In this other conventional device, the heat insulating part 1 having two heat insulating plates 10a and 10b under the crucible 1 is provided.
It has 0. A cooling device 8 that circulates the cooling water 9 is provided below the heat insulating unit 10.

The two heat insulating plates 10a and 10b are
As shown in the plan view of FIG. 8, four holes 11, 11, ... Are provided respectively.

At the time of cooling, as shown in FIG. 9A, the heat insulating plates 10a and 10b are arranged so that the holes 11, 11 ... Overlap each other. With this arrangement, the heat radiation of the molten silicon 3 can be prevented by these holes 1
It will be efficiently carried out through 1, 11 ...

At the time of heating, as shown in FIG. 9 (b), the holes 1 provided in the two heat insulating plates 10a and 10b.
The heat insulating plates 10a and 10a so that 1, 11, ...
0b is arranged. With this arrangement, the crucible 1 can be insulated from the cooling device 8 and the molten silicon 3
Can be efficiently heated.

Therefore, according to the conventional device, the heat conduction can be easily controlled by the arrangement relationship of the two heat insulating plates.

[0015]

However, the above conventional device has the following problems. That is, in the conventional device shown in FIG. 6, since a movable part for moving the cooling part 8 up and down is required, long-term reliability of this movable part has been a problem.

Further, in another conventional apparatus shown in FIG. 7, since the molten silicon 3 is cooled through the holes 11, 11 ... Provided in the heat insulating plates 10a, 10b, uniform cooling is achieved. Not performed, temperature unevenness occurs in the molten silicon 3,
The characteristics of the obtained polycrystalline silicon were non-uniform.

[0017]

In the method for producing a polycrystalline semiconductor according to the present invention, after heating and melting a semiconductor material in a crucible, the semiconductor material is cooled by a cooling device provided through the crucible. In the method of manufacturing a polycrystalline semiconductor to be polycrystallized in, in the heat conduction control unit provided to be in close contact with each other between the crucible and the cooling device, the inside, with a reduced pressure state at the time of heating, It is characterized in that a pressure is applied during the cooling.

The polycrystalline semiconductor manufacturing apparatus of the present invention is a polycrystalline semiconductor manufacturing apparatus including a heat conduction control unit provided in close contact with each other between a crucible and a cooling device, The heat conduction control unit is characterized in that the inside thereof is brought into a depressurized state or a pressurized state, respectively, when heating or cooling the crucible.

[0019]

According to the manufacturing method of the present invention, the heat conduction is suppressed by depressurizing the inside of the heat conduction control portion provided so as to be in close contact with each other between the crucible and the cooling device during heating. Therefore, the raw material silicon in the crucible can be efficiently heated and melted.

Further, at the time of cooling, by enclosing or circulating a gas in the heat conduction control section to bring it into a pressurized state,
Since the heat conduction is improved, the crucible can be effectively cooled by the cooling device. Furthermore, since the heat conduction control unit is provided in close contact with the crucible and the cooling device, it is possible to uniformly cool the molten silicon without causing temperature unevenness,
A polycrystalline semiconductor having uniform characteristics can be manufactured.

In addition, in the manufacturing apparatus of the present invention, the heat conduction control sections for controlling the heat conduction of the crucible are provided in close contact with each other between the crucible and the cooling apparatus, and since there is no movable section, long-term reliability is ensured. It is possible to manufacture a polycrystalline semiconductor having uniform properties and having uniform properties without causing temperature unevenness when the molten semiconductor material is cooled.

[0022]

1 is a schematic structural diagram of an apparatus for producing a polycrystalline semiconductor according to the present invention. In the figure, 10 is a heat conduction control unit, which is a feature of the present invention, 1 is a crucible, and 8 is a cooling unit. The heat conduction control unit 10 includes a gas introduction unit 11 and an exhaust unit 12.

A process for producing polycrystalline silicon using the apparatus of the present invention will be described below.

2A to 2D are explanatory views for each step for explaining the manufacturing method of the present invention.

First, in the first step, FIG.
As shown in FIG. 3, the raw material silicon 2 is put in the crucible 1 and the heat conduction control unit 10 is exhausted from the exhaust unit 12 until the pressure is reduced to 1 Pa or less. In this state, the raw material silicon 2 is heated and melted by using a heater (not shown) to form the molten silicon 3 as shown in FIG. At this time, the heat conduction control unit 10 is depressurized, so that the crucible 1 can be insulated from the cooling device 8, and the raw material silicon 2 can be efficiently heated.

If the heat conduction control section 10 is made of a material having a low heat conductivity, the heat conduction through the surface of the control section 10 is also reduced, which is more effective.

Next, in the second step, the crucible 1
Then, the heating is stopped, and Ar is introduced into the heat conduction control unit 10 from the gas introduction unit 11 to bring it into a pressurized state. By doing so, heat dissipation from the lower part of the crucible 1 can be promoted and efficient cooling can be achieved. Further, since the crucible 1 is cooled uniformly from the surface in contact with the heat conduction control unit 10, there is no temperature unevenness in the molten silicon 3.

At this time, it is not necessary to confine Ar in the heat conduction control unit 10, and Ar or a rare gas such as He or Xe is introduced from the gas introduction unit 11 and exhausted from the exhaust unit 12 so as to conduct heat conduction. You may make it circulate in the control part 10. In addition, the inside of the heat conduction control unit 10 does not necessarily have to have a pressure of atmospheric pressure or more, and may have a pressure of several tens Pa or more.

In this state, the temperature of the molten silicon 3 is lowered to the melting point temperature (1415 ° C.) or lower to solidify, and the polycrystalline silicon 6 is cooled as shown in FIG.

Then, in the third step, the polycrystalline silicon 6 is pulled up as shown in FIG.

Between the second step and the third step, the heat conduction control section 10 may be evacuated again to a reduced pressure state, and the polycrystalline silicon 6 may be annealed at 1200 to 1300.degree. . By doing so, it is possible to prevent the occurrence of cracks in the polycrystalline silicon 6.

As described above, in the device of the present invention,
Since there is no movable part for moving the cooling device 8 up and down like the conventional device, it has long-term reliability. In addition, the crucible 1 can be efficiently heated and cooled, and temperature unevenness does not occur during cooling.

A solar cell was formed using the wafer cut out from the obtained polycrystalline silicon, and its output was measured. FIG. 3 is a characteristic diagram showing an output distribution. Further, FIG. 4 is a distribution of output of a solar cell formed from a polycrystalline silicon wafer manufactured by using another conventional device of FIG. 7.

When this conventional apparatus is used, as described above, the characteristics of the obtained polycrystalline silicon become non-uniform due to temperature unevenness during cooling of the molten silicon. This tendency is particularly remarkable in the lower part of the crucible 1, and as shown in FIG. 4, the output of the solar cell formed using the wafer obtained by slicing from this portion is poor.

On the other hand, when the apparatus of the present invention is used, the molten silicon 3 can be cooled uniformly, so that a uniform output can be obtained as shown in FIG.

In the above embodiments, polycrystalline silicon has been described as an example, but the present invention is not limited to this, and it can be used for manufacturing a general polycrystalline semiconductor.

[0037]

As described above, according to the manufacturing method of the present invention, it is possible to efficiently heat and cool the crucible, and it is possible to manufacture a polycrystalline semiconductor having uniform characteristics.

In addition, since the manufacturing apparatus of the present invention has no movable part, it has long-term reliability.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of a polycrystalline semiconductor manufacturing apparatus of the present invention.

FIG. 2 is an explanatory diagram for each step for explaining the manufacturing method of the present invention.

FIG. 3 is a characteristic diagram showing an output distribution of a solar cell formed by using a wafer cut out from polycrystalline silicon manufactured by the manufacturing apparatus of the present invention.

FIG. 4 is a characteristic diagram showing an output distribution of a solar cell formed by using a wafer cut out from polycrystalline silicon manufactured by another conventional apparatus.

FIG. 5 is an explanatory diagram for explaining a step of manufacturing polycrystalline silicon using a conventional apparatus.

FIG. 6 is a schematic structural diagram of a conventional device.

FIG. 7 is a schematic structural diagram of another conventional device.

FIG. 8 is a plan view of a heat insulating plate.

FIG. 9 is a layout view of a heat insulating plate.

[Explanation of symbols]

1 ... crucible, 8 ... cooling device, 10 ... heat conduction control unit

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Claims (2)

(57) [Claims] 1. A method for producing a polycrystalline semiconductor, comprising: heating and melting a semiconductor material in a crucible; and cooling the semiconductor material by a cooling device provided through the crucible to polycrystallize the semiconductor material. Between the crucible and the cooling device, the inside of the heat conduction control unit provided so as to be in close contact with each other is set to a depressurized state during the heating and a pressurized state during the cooling. Manufacturing method of crystalline semiconductor. 2. A manufacturing apparatus for a polycrystalline semiconductor, comprising a heat conduction control section provided so as to be in close contact with each other between a crucible and a cooling apparatus, wherein the heat conduction control section has An apparatus for producing a polycrystalline semiconductor, which is in a depressurized state or a pressurized state when heating or cooling the crucible, respectively.