JPH1015422A - Crushing method of polycrystalline silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain efficient mass production of lumpy polycrystalline silicon with a simple equipment by heating a cylindrical polycrystalline silicon at a specific temp., thereafter rapidly cooling and crushing with a press. SOLUTION: Then the cylindrical polycrystalline silicon (a silicon rod) obtained by a gas phase reaction, e.g. a 100mm diameter and 80mm length sized rod, is crushed, at first the silicon rod 10 is heated at 400-800 deg.C, and the silicon rod 10 taken out from a heat treating equipment is charged into a water bath to rapidly cool it under 100 deg.C. With this process, a lot of fine cracks are generated in the silicon rod 10 and then the silicon rod 10 is crushed with the press. The press is provided with a stationary board 2 erected on a side edge part of one side of a receiving base 1, and a pressure plate 3 driven back and forth in the direction vertical to the surface of the stationary board 2 on the receiving base 1, and the silicon rod 10 is crushed in a lumpy form by allowing the pressure plate 3 to approach the fixing plate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycrystalline silicon crushing method for crushing rod-shaped polycrystalline silicon into blocks.

[0002]

2. Description of the Related Art A silicon wafer used for a semiconductor device is often industrially obtained from single crystal silicon manufactured by the CZ method. In the production of single-crystal silicon by the CZ method, as is well known, polycrystalline silicon is loaded into a crucible, and the single-crystal silicon is gradually pulled up from a melt obtained by dissolving the polycrystalline silicon. In order to increase the filling rate of the polycrystalline silicon charged in the crucible and increase the size of the single crystal silicon, a bulk material is used for the polycrystalline silicon as a raw material. Since silicon is rod-shaped, it needs to be crushed into blocks when used as a raw material for producing single-crystal silicon.

There are various methods for crushing polycrystalline silicon to obtain massive polycrystalline silicon. Generally, a rod-shaped polycrystalline silicon is rapidly cooled after heating to generate fine cracks therein due to thermal strain. Then, it is a method of crushing by giving an impact with an iron hammer. This method
Since the polycrystalline silicon is easily broken by heating and subsequent quenching, there is an advantage that the burden on the operator can be remarkably reduced as compared with the method of directly breaking the polycrystalline silicon with a hammer.

[0004]

However, even in the case of cracked polycrystalline silicon, a force of 600 kg / cm ² or more is required to crush the polycrystalline silicon. Therefore, crushing with a hammer still imposes a heavy burden on the worker, and the smaller the size to be obtained, the greater the burden, and the throughput per worker is limited to about 300 kg.

In the crushing operation using a hammer, since the surface of the polycrystalline silicon is chipped at the time of hitting, scattering of small pieces and generation of dust are problematic. Since the crushing is performed sequentially toward the center, thin and sharp shapes increase,
There is also a problem that handling is dangerous.

Further, polycrystalline silicon having a size of 10 mm or less after crushing cannot be used as a raw material for melting because it has a large surface area and causes impurities in the raw material melting process. Then 10mm
The following frequently occur, resulting in a loss of about 15% per polycrystalline silicon.

As an alternative to crushing with a hammer, direct crushing with a crushing device such as a jaw crusher is known.
No. 71309. Either method can crush the polycrystalline silicon without burdening the operator.

However, in the former method, since a large load needs to be applied to the polycrystalline silicon, the polycrystalline silicon shatters and shatters in a wide range together with a large plosive sound during crushing. As a result, the scale of the crushing apparatus is increased and the working environment is deteriorated, and a large amount of polycrystalline silicon having an insufficient size is generated, and the loss due to this is comparable to crushing by a hammer. On the other hand, the latter crushing method using high-pressure water injection is not suitable for implementing as a large-scale actual production line because the production amount obtained by one crushing operation is extremely small.

SUMMARY OF THE INVENTION It is an object of the present invention to efficiently mass-produce massive polycrystalline silicon by using a simple apparatus without imposing a burden on an operator, and to generate small pieces that cause loss and thin pieces that are dangerous to handle. It is an object of the present invention to provide a method for crushing polycrystalline silicon, which can suppress as much as possible.

[0010]

In order to achieve the above object, a method for crushing polycrystalline silicon according to the present invention comprises heating a rod-shaped polycrystalline silicon to 400 to 800 ° C., quenching the polycrystalline silicon to 100 ° C. or less, It is crushed by a press machine.

In the crushing method of the present invention, the rod-shaped polycrystalline silicon having a crack therein is crushed instantly by a relatively small load of compression by a press machine. Since the compressive load is small and the crushing is completed instantaneously, the fragments do not scatter, and the dimensions and shape thereof are reduced in the number of thin and sharp pieces and the number of small-sized pieces that cause loss is reduced.

The heating temperature of the rod-shaped polycrystalline silicon is 400
The reason why the temperature is set to 800 ° C. is that when the temperature is lower than 400 ° C., cracks hardly occur in the polycrystalline silicon. This is because it occurs. The reason why the cooling temperature is set to 100 ° C. or less is that if the cooling temperature is higher than 100 ° C., cracks are hardly formed inside the polycrystalline silicon, and crushing by a press causes an increase in the compressive load. As a quenching method,
Water cooling by immersion is desirable from the viewpoint of accelerating the generation of cracks and preventing polycrystalline silicon from being contaminated.

As a press used for crushing, a press provided with a plurality of projections on its pressurized surface is desirable. By providing a plurality of protrusions on the pressing surface, the polycrystalline silicon is temporarily crushed before crushing by the pressing surface, and the crushing load is further reduced. Further, by changing the interval, the crush size can be controlled.

Since the projections are severely worn, SKD, S
It is preferable to use a material having excellent wear resistance, such as S and tool steel, and it is preferable that only the protrusion is replaceable from the viewpoint of repair cost.

The shape of the projection may be plate-like or pin-like, and the shape is not particularly limited. The height of the projection is preferably 25 to 35 mm from the viewpoint of preventing the generation of small pieces that cause loss. The spacing between the protrusions may be constant or irregular,
In short, it is set appropriately according to the size of the lump to be obtained,
One to two times the upper limit of the target size is desirable from the viewpoint of increasing the distribution ratio of the target size and suppressing loss.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing an example of a press machine used in the crushing method of the present invention, FIG. 2 is a front view showing a crushed state by the press machine, and FIG. 3 shows a structure of a cradle portion of the press machine. FIG. 4 is a perspective view, FIG. 4 shows the structure of another press machine, (a) is a plan view, and (b) is a front view.

In this embodiment, rod-shaped polycrystalline silicon (hereinafter, referred to as a silicon rod) having a diameter of 100 mm and a length of 800 mm obtained by a gas phase reaction is crushed. At the time of the crushing, the silicon rod is first heated to about 650 ° C. by a heat treatment apparatus. After heating, the silicon rod taken out of the heat treatment apparatus is put into a water tank in which pure water circulates in an overflow state, and rapidly cooled to room temperature. By this operation, many fine cracks are generated inside the silicon rod.

When a crack is formed, the silicon bar is crushed by a press. As shown in FIG. 1, the press machine includes a fixed platen 2 erected on one side end of a cradle 1.
And a pressure plate 3 which is reciprocally driven on the cradle 1 in a direction perpendicular to the surface of the fixed plate 2 using the cylinder 4 as a drive source. The silicon bar 10 having a crack therein is placed on the receiving table 1 and the pressing plate 3 is moved closer to the fixed plate 2 in this state, whereby the silicon bar 10 is crushed into a block as shown in FIG. .

Here, as shown in FIG. 3, the receiving table 1 is rotatably supported with one end as a fulcrum, and is driven by air pressure. Silicon rod 10 when crushed
The crushed material 11 on the cradle 1 is caused to flow into the storage section 5 below the pedestal 1 by being fixed to a position for horizontally supporting the crushed material and being rotated downward after the crushing.

According to this method, the entire silicon rod 10 can be instantaneously crushed into a lump with a pressure of about 3000 to 3500 kg / cm ² without imposing a burden on the operator. The obtained crushed material 11 has less thin and sharp objects than the case where a cracked silicon rod is crushed by a hammer, and also has a small size of 10 mm or less. The output per worker increases from about 300 kg to over 2000 kg.

When a silicon rod of the same size is directly crushed by a pressing machine without cracking, a pressure of about 10,000 to 35,000 kg / cm ² is required, and a large amount of plosive sound is generated at the time of crushing. Of silicon is shattered and scattered around.

In another press shown in FIG. 4, a plurality of plate-like projections 6 are mounted on the surface of the pressure platen 3 at intervals in the horizontal direction. Here, the dimensions of the projections 6 are 15 mm in thickness and 25 mm in projection height, and the interval is 100 m.
m. When the projections 6 are attached to the surface of the pressure plate 3, the silicon rods 10 are temporarily crushed by the projections 6.
The same size silicon rod 10
When crushing, the pressure required for crushing is about 600 to 7
It is reduced to 00 kg / cm ² .

In this press machine, a concave portion 7 is also provided on the surface of the fixed platen 2 in order to suppress the tendency of the crushed material 11 accumulated below to become too fine when the silicon rod 10 is crushed by pressing. (See FIG. 2), the crushed material 11 escapes into the recess 7 during the crushing process,
Excessive miniaturization can be prevented.

The average size of the bulk polycrystalline silicon obtained by the crushing method of the present invention is shown in Table 1 in the case of using a press with projections. If the target size is S (10
-25 mm), the loss of less than 10 mm is 8%
And the loss is only 3% when the target size is L (45 to 85 mm). In each case, the target size is obtained at a ratio of 50% or more.

[0025]

[Table 1] * Loss refers to a size of 10 mm or less.

In the illustrated example, the press machine presses in the horizontal direction, but it goes without saying that the press machine may be pressurized in a general vertical direction.

[0027]

As described above, according to the method for crushing polycrystalline silicon of the present invention, the rod-shaped polycrystalline silicon after cracking is mechanically crushed by a press machine. Can be greatly reduced, and the production amount can be dramatically increased. Since the load on the press machine is light, the equipment cost is low. Since there is little scattering of the crushed material, deterioration of the working environment is suppressed. Regarding the obtained massive polycrystalline silicon, since the number of thin pieces and sharp pieces is reduced, the handling becomes easy. Since the number of small-sized ones is reduced, the raw material yield is improved.

When the press machine has a projection on its pressurized surface, the load required for crushing is further reduced, so that the scale of the apparatus and scattering of crushed materials are particularly suppressed. Further, the controllability of the crush size is improved.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of a press used in a crushing method of the present invention.

FIG. 2 is a front view showing a crushed state by the press machine.

FIG. 3 is a perspective view showing a structure of a cradle portion of the press machine.

4A and 4B are explanatory views of the structure of another press machine, wherein FIG. 4A is a plan view and FIG. 4B is a front view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cradle 2 Fixed board 3 Pressing board 10 Silicon rod 11 Crushed material

Claims (2)

[Claims] 1. A rod-shaped polycrystalline silicon of 400 to 800
A method for crushing polycrystalline silicon, comprising heating to 100 ° C., rapidly cooling to 100 ° C. or lower, and crushing with a press machine. 2. The method for crushing polycrystalline silicon according to claim 1, wherein said pressing machine has a projection on a pressing surface thereof.