Silicon single crystal manufacturing device

Abstract

The present invention is a device for manufacturing a silicon single crystal by the CZ method, the device comprising: a chamber in which a quartz crucible and a heater for heating and melting a silicon polycrystalline raw material in the quartz crucible to obtain a raw material melt are disposed; a gas introduction pipe; and a gas exhaust pipe. The gas exhaust pipe has a plurality of pipes each having a joint part, and a pipe clamp that can be liquid-cooled by cooling water passing therethrough. The joint parts of the plurality of pipes face each other with a sealing material interposed therebetween, and the plurality of pipes are connected to each other by the facing joint parts being sandwiched by the pipe clamp. The sealing material between the joint parts can be cooled by the liquid cooling of the pipe clamp. As a result, a CZ silicon single crystal manufacturing device is provided in which the gas exhaust pipe is easy to handle and the deterioration of the sealing material between the pipes can be prevented.

Description

Silicon single crystal manufacturing equipment

[0001] The present invention relates to an apparatus for producing silicon single crystals by the Czochralski method (CZ method).

[0002] The Czochralski method is a method for producing silicon single crystals, a basic material for semiconductor integrated circuits. In the CZ method, high-purity polycrystalline silicon raw material is placed in a quartz crucible installed in a chamber and melted by heating using a heater positioned around the periphery of the quartz crucible. A seed crystal is immersed in this raw material melt (molten silicon) and pulled up while rotating, growing a single crystal into a cylindrical silicon single crystal.

[0003] In the CZ method, a vacuum pump is connected to a silicon single crystal manufacturing apparatus (puller) via a gas exhaust pipe, and an inert gas (e.g., Ar gas) introduced into the puller is sucked out by the vacuum pump, which is known as an exhaust method (Patent Document 1).

[0004] JP 2017-114709 A

[0005] In a manufacturing apparatus configured as described above, the gas exhaust piping is made up of multiple pipes connected together, with seals (e.g., O-rings) between the joints. When manufacturing silicon single crystals, the inert gas in the chamber is heated by a heater, resulting in a high temperature. The high-temperature inert gas is exhausted using a vacuum pump, but heat is transferred to the seals through the joints of the gas exhaust piping, causing deterioration, which may result in a leak of the inert gas during silicon single crystal manufacturing. If a leak occurs, the vacuum in the chamber of the silicon single crystal manufacturing apparatus cannot be maintained, which may affect quality.

[0006] If a leak occurs, it is necessary to identify the location of the leak and replace the sealing material, but because there are many pipe joints, inspection takes time, and during that time silicon single crystals cannot be produced.

[0007] Furthermore, since silicon oxide is generated during silicon single crystal production and accumulates in the gas exhaust piping, the gas exhaust piping is removed after the silicon single crystal production, and therefore, for cleaning purposes, a gas exhaust piping (multiple piping) with a structure that is lightweight, easy to handle, and easy to remove is desired.

[0008] FIG. 3 is an explanatory diagram showing an example of a conventional cooling mechanism for a gas exhaust pipe 110. The left diagram of FIG. 3 is an explanatory diagram of the configuration of the gas exhaust pipe 110 as viewed from the axial direction, and the right diagram is an explanatory diagram of the configuration at the B-B' cross section of the left diagram. The joints 115 of two adjacent pipes 112 (112a, 112b) are connected to each other via a sealing material 114 by tightening two annular pipe clamps 113 (113a, 113b) with bolts. In the conventional technology, to prevent the joints 115 from becoming too hot, a water-cooled pipe 120 is wrapped around and welded to the outer periphery of the pipe body of the gas exhaust pipe 110 (i.e., the pipe body of the pipe 112), and water is passed through the water-cooled pipe 120 to prevent the gas exhaust pipe 110 from becoming too hot.

[0009] In the conventional method, the outer periphery of the gas exhaust pipe body is cooled, but the joints and areas around the sealant are not cooled easily, which can cause the sealant to deteriorate due to heat. Furthermore, the gas exhaust pipe must be disassembled and removed when cleaning. However, the water-cooled pipes welded to the pipes, as described above, are heavy, making the work difficult.

[0010] The present invention has been made to solve the above-mentioned problems, and aims to provide a CZ silicon single crystal manufacturing apparatus that makes it easy to handle gas exhaust piping and can prevent deterioration of the sealing material between piping.

[0011] In order to achieve the above object, the present invention provides a silicon single crystal manufacturing apparatus for manufacturing a silicon single crystal from the raw material melt by the Czochralski method, the apparatus comprising: a quartz crucible for accommodating a silicon polycrystalline raw material; and a heater for heating and melting the silicon polycrystalline raw material in the quartz crucible to form a raw material melt; a gas inlet pipe for introducing an inert gas into the chamber; and a gas exhaust pipe for exhausting the inert gas introduced into the chamber; the silicon single crystal manufacturing apparatus is characterized in that the gas exhaust pipe has a plurality of pipes, each having a joint portion, and a pipe clamp that can be liquid-cooled by passing cooling water through it; the joint portions of the plurality of pipes face each other with a sealing material sandwiched between them, and the opposed joint portions are sandwiched between the pipe clamps, thereby connecting the plurality of pipes; and the sealing material between the joint portions can be cooled by liquid-cooling the pipe clamps.

[0012] In the silicon single crystal production apparatus of the present invention, the liquid cooling of the piping clamps can effectively cool the seal between the joints in the gas exhaust piping, preventing thermal degradation of the seal. This eliminates the need for leak inspections and seal replacements that were necessary in conventional apparatuses due to seal degradation, or at least reduces the frequency of such inspections. As a result, maintenance costs can be reduced, and deterioration in the quality of silicon single crystals caused by leaks can be prevented, thereby reducing silicon single crystal production losses.

[0013] Furthermore, because the sealant can be sufficiently cooled without welding a water-cooled pipe to the outer periphery of the pipe body to prevent deterioration of the sealant as in conventional systems, the multiple pipes that make up the gas exhaust pipe can be made lighter and easier to handle. This also simplifies the process of removing deposits from the pipe. Furthermore, the cost of retrofitting using this liquid-cooled pipe clamp is less than the cost of retrofitting using a conventional water-cooled type (where a water-cooled pipe is welded to the outer periphery of the pipe).

[0014] The silicon single crystal manufacturing apparatus of the present invention can prevent deterioration of the seal material in the gas exhaust piping due to heat. Therefore, it is possible to prevent the occurrence of gas leaks caused by deteriorated seal material, and it is possible to prevent the need for various work associated with leaks, the associated costs, and the deterioration of single crystal quality. Moreover, the piping itself is lightweight, which improves the workability of cleaning the inside of the piping.

[0015] FIG. 1 is a schematic side view showing an example of a silicon single crystal manufacturing apparatus of the present invention. FIG. 2 is an explanatory diagram showing an example of the configuration of a gas exhaust piping. The left figure is an explanatory diagram of the configuration as seen from the axial direction. The right figure is an explanatory diagram of the configuration in the cross section A-A' of the left figure. FIG. 3 is an explanatory diagram showing an example of a cooling mechanism for a gas exhaust piping in a conventional apparatus. The left figure is an explanatory diagram of the configuration as seen from the axial direction. The right figure is an explanatory diagram of the configuration in the cross section B-B' of the left figure.

[0016] An example of a silicon single crystal manufacturing apparatus using the Czochralski method of the present invention is shown in Figure 1. This silicon single crystal manufacturing apparatus 1 has a chamber 2. A quartz crucible 4 inside a graphite crucible 3 placed inside the chamber 2 is filled with a raw material melt 5, and a silicon single crystal 6 is pulled up from this raw material melt 5. A heater 7 for heating the raw material melt 5 is installed around the outer periphery of the graphite crucible 3 inside the chamber 2, and a heat insulating member 8 is installed around the outer periphery of this heater 7 to insulate against heat from the heater 7.

[0017] A gas inlet pipe 9 is disposed at the top of the chamber 2, and a gas exhaust pipe 10 is disposed at the bottom. A vacuum pump 11 is connected to the end of the gas exhaust pipe 10. An inert gas such as argon is introduced into the chamber 2 from the gas inlet pipe 9, and the gas flows downward and is exhausted to the outside by the vacuum pump 11 through the gas exhaust pipe 10.

[0018] When producing silicon single crystal 6, first, a silicon polycrystalline raw material is placed in quartz crucible 4 and heated by heater 7 to form raw material melt 5. A seed crystal S suspended by a wire is immersed in raw material melt 5, and then the wire is pulled up to grow silicon single crystal 6. Note that an inert gas is introduced into chamber 2 through gas inlet pipe 9 and exhausted through gas exhaust pipe 10.

[0019] Here, the configuration of the gas exhaust piping 10 in the silicon single crystal manufacturing apparatus 1 of the present invention will be described. An example of the configuration of the gas exhaust piping 10 is shown in Figure 2. The left diagram of Figure 2 is an explanatory diagram of the configuration as seen from the axial direction of the gas exhaust piping 10, and the right diagram is an explanatory diagram of the configuration in the cross section A-A' of the left diagram.

[0020] The gas exhaust pipe 10 mainly includes multiple pipes 12 (12a, 12b), a liquid-coolable pipe clamp 13, and a sealant 14. The pipes 12 themselves may have a joint (e.g., a flange) 15 at their ends. As can be seen particularly in the right diagram of FIG. 2 , a step is provided from the pipe body to the joint 15. However, the shape of the pipe 12 of the present invention is not limited to this, and this step need not exist. Furthermore, examples of the sealant 14 include, but are not limited to, O-rings. As shown in the left diagram of FIG. 2 , the joints 15 of adjacent pipes 12 (12a, 12b) face each other with the sealant 14 sandwiched between them. As shown in the right diagram, the opposing joints 15 are sandwiched between the clamping portions 18 of the pipe clamps 13, thereby connecting the adjacent pipes 12. Note that the solid and dotted circular lines in the left diagram are drawn approximately concentrically, and these represent the pipes 12 and the clamping portions 18. The innermost circular solid line in the left figure represents the inner circumferential surface 12s of the pipe 12 shown in the right figure, and the outermost circular dotted line in the left figure represents the inner bottom surface 18s of the clamp portion 18 shown in the right figure.

[0021] The pipe clamp 13 can be detachable from the pipe 12 (joint 15). Being detachable makes both the pipe clamp 13 itself and the pipe 12 itself easier to handle, and makes it easier to clean the inside of the pipe 12. As an example, as shown in the left diagram of Figure 2, the pipe clamp 13 can have a two-piece structure (13a, 13b) and is made of a material with good thermal conductivity (e.g., aluminum). Of course, the number of pieces is not particularly limited and can be determined appropriately depending on the diameter of the pipe 12, etc.

[0022] The pipe clamp 13 also has a liquid cooling mechanism that uses cooling water to flow through it. For example, it has a through-hole 16 for passing cooling water through it. The inlet of the through-hole 16 has a tapered thread shape for connecting a cooling water supply pipe 17 from the outside. That is, the inlet of the through-hole 16 has an internal thread, and the cooling water supply pipe 17 inserted therein has an external thread. The size (thickness) of the through-hole 16 is not particularly limited, but can be, for example, 40 to 50% of the thickness of the pipe clamp 13. A through-hole 16 with this thickness enables more efficient liquid cooling. Furthermore, the tapered threads (external and internal threads) can be made to match their respective sizes. While the through-hole 16 in FIG. 2 has a linear shape that allows water to flow vertically, this shape is not particularly limited and can be various shapes taking into consideration cooling efficiency, etc. Note that while the type in which the through-hole 16 and the cooling water supply pipe 17 are connected has been described here, it is also possible to use a type in which the cooling water supply pipe 17 passes through the inside of the pipe clamp 13, for example.

[0023] When assembling the gas exhaust pipe 10, the joints 15 of the multiple pipes 12 (12a, 12b) are arranged facing each other with O-rings or other sealing materials 14 sandwiched between them. The two halves of the pipe clamps 13a, 13b are then brought together from the left and right sides of the opposing joints 15, as shown in the left diagram of FIG. 2 . Then, as shown in the right diagram of FIG. 2 , the opposing joints 15 are inserted into the clamp portions 18 of the pipe clamps 13a, 13b and fitted together. The pipe clamps 13a, 13b are then tightened with bolts 19 to form a seal, as shown in the left diagram of FIG. 2 . In the left diagram of FIG. 2 , the joints 15 are visible in the gap between the two left and right pipe clamps 13a, 13b. The cooling water supply pipe 17 is then connected to the pipe clamp 13. In the example shown in FIG. 2 , the cooling water flows from top to bottom, but the opposite direction is also possible. The temperature of the cooling water can be, for example, about 20°C, but is not limited to this. The temperature of the cooling water can be appropriately determined depending on the temperature of the gas in the gas exhaust pipe 10, the distance from the chamber 2, etc. The flow of this cooling water liquid-cools the pipe clamp 13 itself, and can effectively cool the sealing material 14 between the joints 15 sandwiched by the pipe clamp 13.

[0024] In the cooling mechanism for gas exhaust piping in conventional equipment, water-cooled piping was used to cool the joints of multiple pipes (with sealing material between them). However, the cooling mechanism in the manufacturing equipment of the present invention uses liquid-cooled piping clamps that clamp the joints of the pipes (with sealing material between them) as described above, and liquid-cools the piping clamps with cooling water to cool the joints they are holding and the sealing material between them.

[0025] By providing the gas exhaust pipe with this cooling mechanism, the pipe itself is lighter and easier to handle than conventional pipes, and the sealant can be cooled more effectively than conventional pipes, preventing deterioration of the sealant due to the heat of the high-temperature gas passing through the gas exhaust pipe. This not only makes it easier to clean deposits inside the pipe, but also prevents gas leaks due to deterioration of the sealant. This reduces the costs of various tasks such as inspections when leaks occur and maintenance such as replacing the sealant, and prevents the quality of the silicon single crystals produced from being reduced due to gas leaks.

[0026] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A silicon single crystal manufacturing apparatus comprising: a chamber having a quartz crucible for accommodating silicon polycrystalline raw material and a heater for heating and melting the silicon polycrystalline raw material in the quartz crucible to produce a raw material melt; a gas inlet pipe for introducing an inert gas into the chamber; and a gas exhaust pipe for exhausting the inert gas introduced into the chamber, wherein the silicon single crystal is manufactured from the raw material melt by the Czochralski method, the gas exhaust pipe having a plurality of pipes each having a joint portion and a pipe clamp that can be liquid-cooled by passing cooling water through it, the joint portions of the plurality of pipes face each other with a sealing material sandwiched between them, and the opposed joint portions are sandwiched between the pipe clamps to connect the plurality of pipes, and the sealing material between the joint portions can be cooled by liquid-cooling the pipe clamps.

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