JP2009073683A - Apparatus for producing polycrystalline silicon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for producing polycrystalline silicon which can rapidly raise the temperature of a silicon core rod in a reaction furnace and bring the silicon core rod into an energized and heat generation state when operation is started. <P>SOLUTION: The apparatus for producing polycrystalline silicon is provided in which upper end parts of a plurality of silicon core rods 4, arranged at the inner bottom part of a reaction furnace 1 in a standing state, are connected in a pair by a connecting member 12 and at the same time, each of the paired silicon core rods 4 is connected in series between each of a plurality of electrode 5 pairs provided at the inner bottom part of the reaction furnace 1, and then an electric current is caused to flow in the silicon core rods 4 from these electrodes 5 to allow the silicon core rods 4 to generate heat and to deposit polycrystalline silicon on the surface of each core rod 4, wherein a heating device 21 for emitting radiation heat is provided inside the reaction furnace 1 and the silicon core rods 4 are set so that the electric resistance through silicon core rods 4 between electrodes 5 arranged at the positions close to the heating device 21 is lower than the electric resistance through silicon core rods 4 between electrodes 5 arranged at the positions farther from the heating device 21 than the above positions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polycrystalline silicon manufacturing apparatus for manufacturing polycrystalline silicon rods by depositing polycrystalline silicon on the surface of a heated silicon core rod.

  Conventionally, as this type of polycrystalline silicon manufacturing apparatus, a manufacturing apparatus based on the Siemens method has been known. In the polycrystalline silicon production apparatus shown in these patent documents, a large number of seeds made of silicon core rods are placed in a sealed reaction furnace and heated, and the reaction furnace is mixed with chlorosilane gas and hydrogen gas. This is a configuration in which a source gas composed of a gas is supplied, brought into contact with a heated silicon core rod, and polycrystalline silicon generated by thermal decomposition of the source gas is deposited on the surface thereof.

  In such a polycrystalline silicon manufacturing apparatus, the silicon core rod as a seed is fixed upright on an electrode disposed on the inner bottom portion of the reactor, and the upper end portions thereof are connected one by one by a short connecting member. Therefore, it is fixed so as to have a torii shape as a whole. The seed assembly assembled in this manner generates heat due to the resistance heat of the silicon core rod when energized from the electrode during operation, and heats the entire silicon core rod to, for example, 1050 degrees which is the decomposition temperature of the raw material gas. Thus, polycrystalline silicon is deposited on the surface.

In this case, silicon has a remarkably large electrical resistance at room temperature, and shows a specific resistance of about 1000 Ω · cm. When this is heated to around 400 ° C., the specific resistance is drastically reduced to about 1 to 10 Ω · cm and can be energized. Therefore, in the polycrystalline silicon manufacturing apparatus, a heating carbon rod (heating device) is provided at the center or inner peripheral surface of the reaction furnace. Heating the silicon core rod around the rod to a state where it can be energized is performed.
JP 2006-206387 A JP 2001-278611 A JP 2002-338226 A

  By the way, in the polycrystalline silicon manufacturing apparatus described above, at the start of operation, the silicon core rod around the carbon rod is heated by radiant heat from the carbon rod to raise the temperature. There is a problem that it takes a lot of time to raise the temperature until it reaches a temperature, and in order to improve productivity, the heating time is shortened as much as possible, and quickly reaches the decomposition temperature of the raw material gas of 1000 ° C. or higher. It needs to be heated. In addition, since the supply of the raw material gas is generally stopped until the energized heat generation state is reached, the exhaust gas flows back into the reactor and adheres to the surface of the silicon core rod until the energized heat generation state occurs. In addition to contamination, the adhesion between the silicon core rod and the growth layer is deteriorated, for example, causing cracks during production of the recharge rod.

  The present invention has been made in view of the above circumstances, and at the start of operation, the temperature of the silicon core rod in the reaction furnace is quickly raised to an energized heat generation state, improving productivity and improving the quality of silicon. An object of the present invention is to provide a polycrystalline silicon manufacturing apparatus capable of performing

  In order to achieve the above object, the polycrystalline silicon production apparatus of the present invention is configured such that the upper ends of a plurality of silicon core rods erected on the inner bottom of the reaction furnace are coupled one by one by a coupling member, A plurality of pairs of silicon core rods are connected in series between a plurality of pairs of electrodes at the inner bottom of the reactor, and the silicon core rods are heated by energizing the silicon core rods from these electrodes, and the surface In the polycrystalline silicon manufacturing apparatus for depositing polycrystalline silicon, a heating device that emits radiant heat is provided inside the reaction furnace, and the silicon core rod is a silicon core rod between electrodes at a position close to the heating device. The electrical resistance value that passes is set smaller than the electrical resistance value that passes through the silicon core rod between the electrodes farther away.

That is, by setting a small electrical resistance value via the silicon core rod between the electrodes near the heating device, it is easier to raise the temperature of the silicon core rod between the electrodes than other silicon core rods Then, the temperature is rapidly raised by a heating device to obtain an energized heat generation state, and the surrounding silicon core rods are sequentially heated in sequence by the heat generated by the silicon core rods.
When this electrical resistance value is set small, there are a method of reducing the height of the silicon core rod, a method of increasing the thickness, and a method of reducing the number of silicon core rods arranged between the electrodes. However, these may be combined.

In the polycrystalline silicon device of the present invention, the heating device may be provided at the center position of the reaction furnace or near the inner peripheral surface.
When a heating device is provided at the center position of the reaction furnace, the temperature will increase sequentially from the silicon core rod near the center of the reaction furnace, and when a heating device is provided near the inner peripheral surface of the reaction furnace, The temperature rises from the outer peripheral position of the plurality of standing silicon core bars.
When providing a heating device in the vicinity of the inner peripheral surface of the reaction furnace, it may be arranged at one specific location in the circumferential direction of the inner peripheral surface of the reaction furnace, or a plurality of such devices are arranged at regular intervals on the inner peripheral surface of the reaction furnace. May be. When providing a plurality of heating devices, the battery resistance value of the silicon core rod between the electrodes near each heating device may be smaller than the others, but not necessarily all the silicon core rods near all the heating devices. It doesn't have to be small.

   According to the polycrystalline silicon manufacturing apparatus of the present invention, since the electrical resistance value passing through the silicon core rod between the electrodes close to the heating device is set smaller than the others, the temperature of the silicon core rod is increased by the heating device. It can be made easy, and it can be set to an energized heat generation state quickly. Then, the silicon core rods in the vicinity thereof are sequentially heated by the energization heat generation, and all the silicon core rods in the reaction furnace are sequentially brought into the energization heat generation state by the chain. Therefore, at the start of operation, the silicon core rod in the reactor can be raised in temperature in a short time to shift to an energized heat generation state, and the polycrystalline silicon can be precipitated at an early stage, thereby improving productivity. Can be improved. Further, since the time until the energized heat generation state is shortened, the problem of contamination of the silicon core rod is solved, and the quality of silicon can be improved.

Hereinafter, embodiments of a polycrystalline silicon manufacturing apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is an overall view of a reaction furnace 1 of a polycrystalline silicon manufacturing apparatus to which the present invention is applied. A base 2 constituting a furnace bottom and a bell-shaped removably attached to the base 2 are shown. A bell jar 3 is provided.

On the base 2, as shown in FIG. 1, a plurality of pairs of electrodes 5 to which a silicon core rod 4 as a seed rod for the generated polycrystalline silicon is attached, and chlorosilane gas and hydrogen gas are mixed. A plurality of jet nozzles 6 for jetting the raw material gas into the furnace and a plurality of exhaust ports 7 for discharging the reacted gas outside the furnace are provided. These electrodes 5 are arranged substantially concentrically on the base 2 at a constant interval. Further, a plurality of source gas ejection nozzles 6 are provided with appropriate intervals so that the source gas can be uniformly supplied to each silicon core rod 4. These ejection nozzles 6 are connected to a source gas supply source 8 outside the reactor 1. A plurality of exhaust ports 7 are also installed on the base 2 with appropriate intervals and connected to the exhaust gas treatment system 9.
Each electrode 5 is formed in a substantially cylindrical shape made of carbon, and is erected vertically to the base 2. A hole is formed along the axis of the electrode 5, and a lower end portion of the silicon core rod 4 is formed in the hole. Is installed in the inserted state.

These silicon core rods 4 are vertically extended as shown in FIGS. 1 and 2 by being fixed in a state where the lower end portions are inserted into the electrodes 5. One short connecting member 12 is attached to the upper end so as to be connected as a pair. This connecting member 12 is also formed of the same silicon as the silicon core rod 4. The seed assembly 13 is assembled by the two silicon core rods 4 and the connecting member 12 that connects these two so as to form an inverted U-shaped torii shape as a whole.
As shown in FIG. 2, these seed assemblies 13 are arranged almost concentrically as a whole because the electrodes 5 are arranged concentrically from the center of the reaction furnace 1, but are not necessarily all concentric. The configuration may be such that a part of the silicon core rods are arranged in the radial direction or the like.

A heating device 21 is provided at the center of the reaction furnace 1. The heating device 21 of this embodiment is configured by a carbon heater 22, and is configured such that an inverted U-shaped carbon heater 22 is erected on an electrode 23 on the base 2.
Then, the silicon core rod 4 of the seed assembly 13 closest to the heating device 21, in other words, silicon in the seed assembly 13 at the innermost peripheral position shown by A in FIGS. 2 and 3 among the silicon core rods 4. The core rod 4 is set to have a height smaller than that of the silicon core rod 4 in the other seed assembly 13 disposed outside the core rod 4. For example, the silicon core rod 4 at the innermost peripheral position has a height of 200 cm, and the other silicon core rods 4 have a height of 220 cm.
In addition, the said heating apparatus 21 is set to the height corresponding to the full length of the silicon | silicone core rod 4, so that radiant heat can be irradiated to the full length of the silicon | silicone core rod 4 of an innermost periphery position.

In the polycrystalline silicon manufacturing apparatus configured as described above, the heating device 21 disposed at the center of the reaction furnace 1 and the electrodes 23 and 5 connected to the silicon core rods 4 are energized, respectively. At this time, since the heating device 21 is the carbon heater 22, the heating device 21 generates heat before the silicon core rod 4 and the temperature rises. It is transmitted to the silicon core rod 4 and heated from the outer surface.
At this time, since the silicon core rod 4 in the seed assembly 13 at a position close to the heating device 21 shown by A in FIGS. 2 and 3 is smaller than the other silicon core rods 4, the temperature is quickly increased by radiant heat. Raised. When the temperature of the silicon core rod 4 rises to a state where it can be energized, a resistance heat is generated by energization from its own electrode 5, and the heat is transmitted to the adjacent silicon core rods 4 adjacent to the silicon core rod 4. The rod 4 is heated, and the heat transfer phenomenon is propagated one after another in the radial direction of the reaction furnace 1 and finally all the silicon core rods 4 in the reaction furnace 1 are energized to be in a heat generation state. When the silicon core rod 4 rises to the decomposition temperature of the source gas, the source gas ejected from the ejection nozzle 6 deposits polycrystalline silicon on the surface of the silicon core rod 4.

  That is, in the polycrystalline silicon manufacturing apparatus having this configuration, the silicon core rod 4 in the seed assembly 13 closest to the heating apparatus 21 is first heated by the radiant heat from the heating apparatus 21 to a state where it can be energized. After being raised, this is energized and heated, and the surrounding silicon core rod 4 is heated by the heat and propagated in the radial direction, etc., so that the whole is energized and heated. In that case, the heat is generated first. By reducing the height of the silicon core rod 4 to be in a state so that the temperature easily rises due to heating, the temperature of the silicon core rod 4 can be quickly raised to bring the entire energized heat generation state in a short time. It can be done.

In the present embodiment, the height of all the silicon core rods 4 (three sets of seed assemblies shown by A in FIG. 2) of the seed assembly 13 at the innermost peripheral position is set to the height of the silicon cores of the other seed assemblies 13. The height of the rod 4 is set lower than that of the rod 4, but the present invention is not limited to this. The height of only one set of the three sets of seed assemblies 13 shown in FIG. It may be configured such that only one set of seed assemblies 13 is immediately brought into an energized heat generation state, and then the other sets of seed assemblies 13 in the vicinity are sequentially heated.
Further, in the present embodiment, the heights of the silicon core rods 4 of the seed assembly 13 other than the innermost seed assembly 13 are all the same height, but the present invention is not limited to this. As shown, the height of the silicon core 4 of the seed assembly 13 may be increased stepwise as the distance from the heating device 21 increases. In the polycrystalline silicon manufacturing apparatus shown in FIG. 4, each seed assembly 13 arranged concentrically around the heating device 21 as in the example shown in FIG. The height of the silicon core rod 4 is changed every 13 and the height is gradually increased from the heating device 21 toward the outside in the radial direction in the order indicated by A, B, and C in FIG.

  Further, in each of the above embodiments, the heating device 21 is provided at the central position of the reaction furnace 1, and the height of the seed assembly 13 at the innermost peripheral position located in the vicinity thereof is set lower than the other seed assemblies 13. However, the present invention is not limited to this, and as shown in FIG. 5, the heating device 31 that is a heat source may be arranged near the inner peripheral surface of the reaction furnace 1, and in that case, near the heating device 31. The silicon core rod 4 of the seed assembly 13 located in the vicinity of the heating device 31 at the outermost peripheral position indicated by D in FIG. 5 so that the silicon core rod 4 of the seed assembly 13 positioned first shifts to the energized heat generation state. May be set lower than the other silicon core rods 4. In this case as well, only the height of the silicon core rod 4 of the seed assembly 13 closest to the heating device 31 is set small in FIG. 5, but the height of the silicon core rod 4 is increased stepwise as the distance from the heating device 31 increases. You may make it set.

Further, when the heating device 31 is provided in the vicinity of the inner peripheral surface of the reaction furnace 1, a configuration in which a heating device is provided at one specific location in the circumferential direction may be employed, or a heating device may be provided at a plurality of locations in the circumferential direction, The height of the silicon core rod of the seed assembly in the vicinity of the apparatus may be set low.
Furthermore, as a heating device, a heating device having an infrared irradiation type filament can be applied besides the carbon heater.
In any of the embodiments, the height of the silicon core rod in the vicinity of the heating device is set to be smaller than that of other silicon core rods, but the height is not changed from that of other silicon core rods. It is good also as a structure which enlarges, and it is good also as the setting which made height small and enlarged thickness. Furthermore, in the said embodiment, although two silicon core rods were installed between the electrodes as a pair, these may be installed in a series connection state between the electrodes as a set of a plurality of pairs (for example, four), In this case, a pair of (2) silicon core rods are provided between the electrodes in the vicinity of the heating device, and two pairs (4) silicon core rods are provided between the other electrodes. It is good also as a state which is easy to generate heat. That is, the electrical resistance value passing through the silicon core rod between the electrodes in the vicinity of the heating device may be set smaller than the electrical resistance value passing through the silicon core rod between the other electrodes. For example, the electrical resistance value in the vicinity of the heating device may be about 0.7 to 0.95 times the electrical resistance value of other devices.

It is the perspective view which notched the bell jar of the reaction furnace partially. It is a cross-sectional view of the reactor shown in FIG. It is a longitudinal cross-sectional view for showing the height of the silicon | silicone core rod in the reaction furnace of FIG. FIG. 4 is a vertical cross-sectional view similar to FIG. FIG. 4 is a longitudinal sectional view similar to FIG. 3 showing the height of the silicon core rod when the heating device is installed near the outer periphery of the reaction furnace.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor 2 Base 3 Belger 4 Silicon core rod 5 Electrode 6 Injection nozzle 7 Exhaust port 8 Raw material gas supply source 9 Exhaust gas treatment system 12 Connecting member 13 Seed assembly 21 Heating device 22 Carbon heater 23 Electrode 31 Heating device

Claims (6)

The upper ends of a plurality of silicon core rods erected on the inner bottom portion of the reaction furnace are connected to each other by a connecting member, and the silicon core rods forming a pair are connected between a plurality of sets of electrodes on the inner bottom portion of the reaction furnace. In a polycrystalline silicon manufacturing apparatus in which a plurality of pieces are connected in series, and the silicon core rod is heated by energizing the silicon core rod from these electrodes to deposit polycrystalline silicon on the surface thereof.
A heating device for releasing radiant heat is provided inside the reaction furnace,
The silicon core rod is set such that the electrical resistance value passing through the silicon core rod between the electrodes near the heating device is smaller than the electrical resistance value passing through the silicon core rod between the electrodes farther than this. A polycrystalline silicon manufacturing apparatus characterized by that.   The height of the silicon core disposed between the electrodes near the heating device is set to be smaller than the height of the silicon core disposed between the electrodes farther than this. The polycrystalline silicon manufacturing apparatus according to claim 1.   The thickness of the silicon core rod disposed between the electrodes close to the heating device is set larger than the thickness of the silicon core rod disposed between the electrodes farther than this. The polycrystalline silicon manufacturing apparatus according to claim 1 or 2.   The number of silicon core rods disposed between the electrodes at positions close to the heating device is set to be smaller than the number of silicon core rods disposed between the electrodes at positions farther from this. The polycrystalline silicon manufacturing apparatus according to any one of claims 1 to 3.   The polycrystalline silicon manufacturing apparatus according to any one of claims 1 to 4, wherein the heating device is provided at a central position of a reaction furnace.   The polycrystalline silicon manufacturing apparatus according to any one of claims 1 to 4, wherein the heating device is provided in the vicinity of an inner peripheral surface of a reaction furnace.

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