DEVICE AND METHOD FOR THE REMOVAL OF POLYCRYSTALLINE SILICON RODS FROM A REACTOR

Abstract

A device for removing polycrystalline silicon rod pairs from a Siemens reactor has a body dimensioned to fit over a single rod pair. Once the rod pair is within the body, the body and enclosed rod pair is removed.

Claims

1. A device for the removal of polycrystalline silicon rods from a reactor containing U-shaped rod pairs, comprising a body having an outer wall, an inner wall which is dimensioned such that it can completely enclose one U-shaped rod pair, an opening at a lower end thereof, and a closable flap to close said opening and minimize contamination wherein the body having the U-shaped rod pair is capable of being lifted in such a manner that the body together with the one U-shaped rod pair can be removed from the reactor.

2. The device of claim 1, wherein the body is dimensioned such that the length thereof corresponds to at least the height of the one U-shaped rod pair and an internal width thereof corresponds to at least the width of the one U shaped rod pair.

3. The device of claim 1, wherein the body has an inner wall made of steel and the rod pair is covered with a plastic bag prior to enclosure with the body.

4. The device of claim 1, wherein the body is made of a low-contamination hard metal, or is made of a plastic.

5. The device of claim 1, wherein the body has an inner wall made of steel which is coated with a plastic.

6. The device of claim 1, wherein the body has an inner wall made of steel which is partially or completely coated with a low-contamination hard metal.

7. The device of claim 1, wherein the body is a flexible body made up of a plastic material.

8. The device of claim 1, wherein the body walls are sized such that the body may enclose rods in a Siemens reactor having a closeness ratio of from 0.2 to 0.5.

9. The device of claim 8, wherein the body has walls of steel coated with plastic such that a rod pair enclosed within the body can directly contact each wall without contamination.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 illustrates one embodiment of a device of the invention.

DETAILED DESCRIPTION

[0021] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0022] The body (1) is preferably dimensioned in such a manner that the length (L) thereof corresponds to at least the height (H) of the vertical rod pair (4). Preferably, the length is at least 2.5 m.

[0023] The width (Wi) of the body is preferably at least the width (W) of a U shaped silicon rod pair (silicon bridge+rod diameter). Preferably, the width is at least 200 mm, more preferably at least 300 mm.

[0024] It has been found that a particularly safe and low-contamination removal of the silicon rods can be ensured when the body is configured with respect to the maximum width and depth thereof in such a manner that the distance from the adjacent rod pairs is a minimum of 1 cm. As a result, even rods that have grown crooked or highly club-shaped can be removed.

[0025] The removal of unstable polysilicon rods (e.g. having a high popcorn fraction, that is to say high surface roughness, or instability due to jumps on the silicon rod) is possible without problems. In particular, there is no danger that the total batch or individual rod pairs could fall down during the removal process.

[0026] Since rod removal proceeds pairwise, each silicon rod pair can be removed at any desired point in time. In particular, removal from the interior outwards is possible, which was not provided for with devices of the prior art. A targeted removal of a defined rod pair thus does not pose any difficulties.

[0027] Preferably, the body has an inner wall (3) made of steel. The inner wall of the body can be coated with a polymer. Preferably, the body consists of steel, that is to say comprises a steel shell.

[0028] Particular preference is given to an embodiment which provides a body having an uncoated steel inner wall, wherein the silicon rod pair is covered during removal with a plastic bag. This embodiment is particularly space-saving when the steel wall is as thin as possible. Coating the steel inner wall is not required in this case, since the plastic bag protects the silicon against contamination.

[0029] As an alternative to the uncoated steel wall in combination with a plastic bag, particular preference is also given to an embodiment of the body comprising a low-contamination hard metal (e.g. tungsten carbide, TiN or others) or otherwise, a low-abrasion ceramic.

[0030] Preference is also given to the use of a body containing a steel inner wall, wherein the inner wall of the body is partially or completely coated with such a low-contamination hard metal, or with a low-abrasion ceramic.

[0031] It is likewise preferred that the body consists of a flexible, but stable, plastic. Possible plastics here are a fiber composite plastic made of an aromatic polyamide (aramid fibers) or of a polyester such as polycarbonate or polyethylene terephthalate. Equally, materials of carbon or carbon components or glass fiber-reinforced plastics (GRP) are possible.

[0032] The silicon rod pair itself can be lifted out with the aid of a crane device, a cable hoist, or comparable systems.

[0033] Preferably, the body comprises at an opening (7) of the body a flap (5) which is closable manually or by means of a mechanical or electrical mechanism (8), in such a manner that the U-shaped rod pair may be enclosed completely in the body and thus may be lifted out of the reactor. The rod pair that has been lifted out is transported away to further processing operations preferably by means of a transport truck.

[0034] The use of grippers is also possible in order to remove the rods pairwise from the reactor. The grippers are preferably dimensioned in such a manner that they have a radius as small as possible and, even in the case of closely arranged rods in the reactor, still permit safe fixing of the rod pairs. A low-contamination and safe removal of the rod pairs by means of such grippers does not pose any difficulties. However, when such grippers are used, there is the disadvantage that, as in some solutions of the prior art, it is only possible to remove the rods from the outside towards the inside.

[0035] The invention permits the removal of very large silicon rods from a reactor without damaging or contaminating them.

[0036] By means of the invention it is possible to deposit the maximum rod diameter. The maximum possible rod diameter depends solely on the arrangement of the rods in the reactor and on the deposition process. To date, the deposition of rods having the maximum possible rod diameter was not possible, because there was no known possibility of removing such rods in a safe and low-contamination manner.

[0037] Also, inclined or club-shaped rods, likewise rods having high surface roughness or rods deposited in an unstable manner (having increased porosity), or mutually touching rods, can be removed without difficulties.

[0038] The invention may display its advantages, particularly, when the rods in the reactor are arranged particularly close.

[0039] The closeness in the reactor may be defined as the ratio of maximum silicon rod cross section of a batch divided by the area spanned by the reactor internal diameter. At a ratio between 0.2 and 0.5, it is not possible to remove rods pairwise by the known prior art. The devices according to US 20120237678 A1 and US 20100043972 A1, in contrast to the present invention, do not permit individual pairwise removal of very thick rods (closeness 0.2-0.5), since position and size of the rods are greatly restricted by the predetermined chambers in the removal system. If the rod diameters increase beyond the possible closeness factor (even if only for a few rod pairs in the entire reactor), both removal systems can no longer be used for removing the rods, since the excessively thick or inclined rods do not fit into the chambers provided therefor. In this case, attempts must be made by hand to remove the rods individually. This is very time-consuming, causes increased contamination of the silicon, and in addition is hazardous for the personnel (rods can drop down). In the worst case, the entire batch must be intentionally discarded.

[0040] The present invention provides that the rod removal proceeds pairwise, and the deposition reactor comprises an even number of rods. Preferably, the number of rods is at least 24. The rods preferably have a diameter of at least 145 mm.

[0041] While various embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.