JP2006143552A - Method for packing polycrystalline silicon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide such a shape of a packing material which provides the surface of the packing material from being chipped due to rubbing together of a massive polycrystalline silicon and the packing material in such a manner that the degradation in the quality of the polycrystalline silicon is not induced when packing the massive polycrystalline silicon. <P>SOLUTION: (1) The method for packing the polycrystalline silicon comprises confining the area that the massive polycrystalline silicon and the packing material can be in contact with each other is confined to 580 cm<SP>2</SP>per 1 kg of the polycrystalline silicon, at the time of packing the massive polycrystalline silicon. (2) The method for packing the polycrystalline silicon, as described in the (1), in which the grain size of the massive polycrystalline silicon is 3 to 120 mm. (3) The method for packing the polycrystalline silicon, as described in the (1), in which the packing material is made of a resin composed of a plane, and a curved surface and their combination. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for packing polycrystalline silicon used as a melting raw material when producing a silicon single crystal by the Czochralski method (hereinafter simply referred to as “CZ method”), and more particularly, bulk polycrystalline silicon and a packing material. It is related with the packing method of the polycrystalline silicon which prevents the deterioration of the quality of a polycrystalline silicon by adjusting the area which can contact.

  Usually, the CZ method is widely used for the production of silicon single crystals for semiconductors. In recent years, in an apparatus for pulling large and long silicon single crystals by the CZ method, about 100 kg of polycrystalline silicon is charged into a quartz crucible, and the silicon single crystal is pulled after melting. At this time, in order to improve the volumetric efficiency in the quartz crucible, rod-like polycrystalline silicon and massive polycrystalline silicon obtained by crushing rod-like polycrystalline silicon are charged at a high density.

  Polycrystalline silicon produced by the Siemens method is obtained as a rod having a diameter of 110 to 160 mm. This is cut into a predetermined length by a diamond cutter or the like to form rod-shaped polycrystalline silicon, and the rod-shaped polycrystalline silicon is crushed to form massive polycrystalline silicon having a particle diameter of 3 to 120 mm. Usually, when charging into the above-described quartz crucible, the bulk polycrystalline silicon has a particle size such as bulk polycrystalline silicon crushed to a particle size of 3 to 45 mm or bulk polycrystalline silicon crushed to a particle size of 40 to 120 mm. Often packed and transported separately. When producing a silicon single crystal by the CZ pulling method, the bulk polycrystalline silicon to be filled in the crucible is several kg to several tens kg in one variety, and several kg to several tens of kg per bag in consideration of handling etc. kg of polycrystalline silicon is packed in a rectangular parallelepiped packing material. Further, as a material of the packing material, a resin bag such as a polyethylene resin is used in consideration of the thickness so as not to be broken during transportation.

  However, since the bulk polycrystalline silicon obtained by cutting and crushing rod-shaped polycrystalline silicon produced by the Siemens method is a brittle material, the edges of the cut surface and the crushing surface must be sharp. There are many. Therefore, when transporting after packing, a cushioning material such as foamed polystyrene is used to prevent vibration, but the surface of the packing material such as polyethylene resin may be scraped and pulverized to adhere to the surface of the massive polycrystalline silicon. . When the fine powder such as polyethylene resin adhering in this way is put into the above-mentioned quartz crucible together with the bulk polycrystalline silicon, the quality of the silicon single crystal is deteriorated.

  It is well known that fine powder such as polyethylene resin as a packaging material adhering to polycrystalline silicon is one of the causes of quality deterioration of silicon single crystals. For example, in Patent Document 1, there is a foreign substance called particles such as metal powder that adheres when cutting rod-shaped polycrystalline silicon and crushing it, and fine resin powder that adheres during transportation. Explained. In Patent Document 1, a predetermined amount of polycrystalline silicon to which such metal powder or resin powder that causes such quality deterioration is immersed in a chemical solution, and the surface thereof is dissolved, so that these are dissolved in the chemical solution. An evaluation method has been proposed in which a chemical is suspended and the number of foreign substances is measured using an inspection device such as a particle counter.

  In Patent Document 2, in order to prevent the generation of fine powder from the packing material, a method is proposed in which massive polycrystalline silicon is brought into close contact with the packing material and is vacuum-packed and transported so as not to rub against each other.

  According to the transport method of Patent Document 2, it is proposed to use a so-called vacuum packaging using a gas poorly permeable film such as a polyethylene film having a thickness of 0.1 to 0.3 mm as a packaging material. The bulk polycrystalline silicon and the packing material have a tightening effect by reducing the pressure by setting the pressure in the packing material to 0.3 to 0.95 times the atmospheric pressure, and the packing material and the bulk polycrystalline It is said that a sufficient contact area with silicon can be secured and fixed by adhesion.

  However, in the method proposed in Patent Document 2, since the massive polycrystalline silicon and the packaging material are in close contact with each other during decompression packaging, the packaging material may rub and fine powder may be generated.

Japanese Patent Laid-Open No. 2002-5812 JP 2002-68725 A

  As described above, in the conventional polycrystalline silicon packing method, the bulk polycrystalline silicon and the polyethylene resin of the packing material rub against each other and the surface thereof is scraped into fine powder, which adheres to the surface of the bulk polycrystalline silicon, There is a problem of deteriorating the quality of silicon single crystals. Therefore, reduction of the number of fine powders adhering to the surface of massive polycrystalline silicon at the time of unpacking is required.

  The present invention has been made in view of the above-described conventional problems, in the case where rod-like polycrystalline silicon obtained by the Siemens method is cut and crushed massive polycrystalline silicon is packed in a packing material such as polyethylene resin. In addition, a method for packing polycrystalline silicon that reduces the number of fine powders adhering to the surface of the bulk polycrystalline silicon generated by rubbing by managing the area where the bulk polycrystalline silicon and the packing material can contact each other is provided. The purpose is to do.

  In order to solve the above-mentioned problems, the present inventor is able to contact the bulk polycrystalline silicon and the packing material per unit weight of the bulk polycrystalline silicon after shipment, and the number of fine powders adhering to the bulk polycrystalline silicon. A detailed study was made on the correlation with the.

  As a result of the investigation, the area of contact between the bulk polycrystalline silicon and the packing material per unit weight of the bulk polycrystalline silicon and the number of fine powders adhering to the surface of the bulk polycrystalline silicon have inflection points at predetermined values, respectively. It was found that the number of fine powders adhering to the massive polycrystalline silicon surface suddenly increases when the contactable area increases beyond the inflection point. Based on this knowledge, high quality polycrystalline silicon can be provided to customers by managing the area where the bulk polycrystalline silicon and the packing material can be contacted to an area smaller than the inflection point.

  The present invention has been completed on the basis of the above examination results, and the gist of the following (1) to (3) packing method for polycrystalline silicon.

(1) When packing bulk polycrystalline silicon, the area where the bulk polycrystalline silicon can come into contact with the packing material is 580 cm ² or less per kg of the bulk polycrystalline silicon, Is the method.

  (2) The method for packing polycrystalline silicon according to (1) above, wherein the bulk polycrystalline silicon has a particle size of 3 to 120 mm.

  (3) The method for packing polycrystalline silicon according to (1) above, wherein the packing material is made of a resin composed of a flat surface, a curved surface, and a combination thereof.

  The “area where the massive polycrystalline silicon can come into contact with the packing material” in the present invention is an inner surface area of the packing material for packing the massive polycrystalline silicon. At this time, the packing material is filled with massive polycrystalline silicon as close as possible.

Further, “580 cm ² or less per 1 kg of massive polycrystalline silicon” defined by the present invention means an area obtained by dividing the area that can be contacted when packing massive polycrystalline silicon by the weight of the packed polycrystalline silicon. Is 580 cm ² or less.

  According to the method for packing polycrystalline silicon of the present invention, when packing the bulk polycrystalline silicon, by controlling the area where the bulk polycrystalline silicon and the packing material can come into contact with each other, The generation of fine powder can be reduced to a certain amount or less even when the bulk polycrystalline silicon and the packing material rub against each other.

  In the packing method of the present invention, the area that can be contacted between the bulk polycrystalline silicon and the packing material is determined according to the particle size of the bulk polycrystalline silicon according to the above-described investigation. This is an invention based on the knowledge that the number of fine powders adhering to the massive polycrystalline silicon suddenly increases when it has an inflection point and the contact area exceeds the inflection point. From this, it is possible to provide high-quality polycrystalline silicon to customers by managing the packing weight and packing shape so that the contact area is less than these inflection points.

  In addition, by forming the packing material into a spherical shape or a shape close to a cube or the like where the area that can be contacted per volume is the smallest in advance, the area that can be contacted with the packing material per 1 kg of bulk polycrystalline silicon is normally used as a rectangular parallelepiped. It can be reduced more than the shape, and even higher quality polycrystalline silicon can be provided even with the same weight packaging. Furthermore, in the packing shape, for example, in the rectangular parallelepiped shape, the packing material is formed into a shape including a curved surface even when the contactable area per kg of massive polycrystalline silicon exceeds the area at the inflection point. In some cases, the contactable area can be made equal to or less than the area at the inflection point.

  In addition, bulk polycrystalline silicon used for the production of a silicon single crystal for semiconductors is usually used having a particle size of 3 to 120 mm. However, when packing bulk polycrystalline silicon, the silicon single crystal pulling crucible is filled at a high filling rate, so that the particle size is 2 to 45 mm or 40 to 120 mm as described above. It may be packed and used properly.

  The packing material proposed in the present invention has a shape composed only of a plane (such as a cube), a shape composed of a combination of a plane and a curved surface (such as a bowl), and a curved surface such as a sphere. There is a shape and the like, and it is not particularly limited.

  As described above, the method of measuring the area where the bulk polycrystalline silicon and the packing material can be contacted uses a packing material formed in a shape that reduces the area per volume that can be contacted in advance. Can be easily obtained.

  As a method of measuring the number of fine powders adhering to massive polycrystalline silicon, when pulling up large and long silicon single crystals by the CZ method, fine powders with a particle size of 0.2 to 5 μm are silicon single crystals. As the main cause of quality deterioration, the surface of the unpacked bulk polycrystalline silicon is dissolved with an acid solution, and the number of fine particles with a particle size of 0.2-5 μm is inspected by a particle counter, etc. Use to measure. In this case, after transporting for 5 hours after packing, 1 kg of massive polycrystalline silicon is randomly collected, and 800 ml of hydrofluoric acid (hydrofluoric acid: nitric acid = 1: 10 mixture) is used for 120 minutes of massive polycrystalline silicon. The resin fine powder adhering to the bulk polycrystalline silicon is recovered in the acid, and 200 cc of hydrofluoric acid is further added to completely dissolve the remaining silicon powder to obtain a fine powder measurement sample solution.

In addition, the number of fine powders adhering to the bulk polycrystalline silicon is evaluated by using a packing material having a rectangular parallelepiped shape, using bulk polycrystalline silicon having a particle size of 40 to 120 mm, and an area that can be contacted per 1 kg of silicon. Is a method of expressing the maximum number of fine powders in the case of 600 to 640 cm ² as a reference value as a relative value. For example, in the case of using bulk polycrystalline silicon having a particle size of 40 to 120 mm, if the area that can be contacted per 1 kg of silicon is 400 cm ² , this relative value (hereinafter referred to as “the relative number of fine powders”) is: It becomes almost 70%, and the number of fine powders adhering greatly decreases.

As described above, the contact area between the bulk polycrystalline silicon and the packing material is determined by the shape and size of the packing material, but the contact area per kg of the bulk polycrystalline silicon is the grain size of the bulk polycrystalline silicon. It depends on. For example, when using bulk polycrystalline silicon having a particle size of 40 to 120 mm and packing material having a spherical shape with a diameter of 27 cm, the filling weight is 10 kg, and the area that can be contacted is 230 cm ² per kg of bulk polycrystalline silicon. Become. In this case, the relative value of the number of fine powders adhering to 1 kg of massive polycrystalline silicon when transported and unpacked for 5 hours after packing is approximately 60%.

As another example, in a cubic shape in which the vertical, horizontal, and height dimensions are 22 cm when the filling weight is approximately 10 kg as described above, the contactable area is 290 cm ² per 1 kg of massive polycrystalline silicon. In addition, the fine powder number relative value of the fine powder adhering to the massive polycrystalline silicon is 61%. On the other hand, when the area that can be contacted per 1 kg of silicon is 600 to 640 cm ² in the rectangular parallelepiped shape as described above, the relative value of the number of fine powders is 100%.

  Thus, by using the packing material formed in such a shape that the contactable area such as the spherical shape or the cubic shape becomes small, the contactable area per 1 kg of the massive polycrystalline silicon becomes small, and the massive polycrystalline silicon. It can be seen that the number of fine powders adhering to is reduced.

  Below, the effect by the packing method of the polycrystalline silicon of this invention is demonstrated below.

FIG. 1 shows the relationship between the area that can be contacted per 1 kg of silicon and the relative number of fine powders adhering to the bulk polycrystalline silicon when packing the bulk polycrystalline silicon having a particle size of 40 to 120 mm. FIG. According to FIG. 1, an inflection point is an area of 580 cm ² that can be contacted per 1 kg of silicon when the packing material is packed in various shapes. It can be seen that when the inflection point exceeds 580 cm ² , the number of fine powders increases rapidly. In addition, when the area that can be contacted per 1 kg of silicon serving as the inflection point is 580 cm ² , the relative value of the number of fine powders is approximately 80%.

FIG. 2 shows the relationship between the contactable area per kg of silicon and the relative number of fine powders adhering to the massive polycrystalline silicon when packing the massive polycrystalline silicon having a particle diameter of 3 to 45 mm. FIG. In FIG. 2, an area of 340 cm ² that can be contacted per 1 kg of silicon is an inflection point. And if it exceeds 340 cm < ² > used as this inflection point, the number of fine powder will increase rapidly. Furthermore, according to FIG. 2, even if the area that can be contacted per 1 kg of silicon is 580 cm ² , the relative number of fine powders is approximately 80%.

Therefore, from the example of FIGS. 1 and 2, the area that can be contacted per kg of silicon when packing bulk polycrystalline silicon should be controlled to at least 580 cm ² or less, and further to be below the inflection point. If managed, the number of fine powders can be efficiently reduced. For this purpose, the packing shape may be selected as appropriate according to the particle size and amount of the bulk polycrystalline silicon to be packed, and an area where contact can be made.

  According to the method for packing polycrystalline silicon of the present invention, the generation of fine powder during transportation can be reduced by reducing the area where the bulk polycrystalline silicon and the packing material can be contacted. Can prevent quality deterioration. Thus, the polycrystalline silicon packaging method of the present invention can be applied in a wide range of fields when packaging and transporting polycrystalline silicon produced by the Siemens method.

It is a figure which shows the relationship between the area which can contact per kg of silicon | silicone, and the relative number of fine powders of the fine powder adhering to massive polycrystalline silicon when packing massive polycrystalline silicon with a particle size of 40-120 mm. It is a figure which shows the relationship between the area which can contact per kg of silicon | silicone, and the relative number of fine powders of the fine powder adhering to massive polycrystalline silicon when packing massive polycrystalline silicon with a particle size of 3-45 mm.

Claims (3)

A packing method for polycrystalline silicon, characterized in that, when packing bulk polycrystalline silicon, an area where the bulk polycrystalline silicon and the packing material can come into contact is 580 cm ² or less per kg of the bulk polycrystalline silicon.   2. The method for packing polycrystalline silicon according to claim 1, wherein the bulk polycrystalline silicon has a particle size of 3 to 120 mm. 2. The method for packing polycrystalline silicon according to claim 1, wherein the packing material is made of a resin composed of a flat surface, a curved surface, and a combination thereof.

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