Polycrystalline silicon manufacturing equipment

Abstract

To reduce the attachment of byproducts to the internal surface of a bell jar.SOLUTION: A device for producing polycrystalline silicon has a bottom plate (2) with plural pairs of electrodes (4) disposed on n concentric circles. In a horizontal cross section of the bottom plate (2), the center of the concentric circles is considered as the inside, and the edge of the bottom plate is considered as the outside, where all supply nozzles (6) are disposed outside the n-th concentric circle from the inside.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an apparatus for manufacturing polycrystalline silicon.

Background Art

[0002] As a method for industrially manufacturing polycrystalline silicon used as a raw material for semiconductor or photovoltaic wafers, the Siemens method is known. In the Siemens method, a silicon deposition core wire (hereinafter sometimes referred to as a "silicon core wire") erected inside a bell-shaped (bell jar type) reactor is energized and heated to a silicon deposition temperature (about 600°C or higher), and a raw material gas containing a gas of a silane compound and hydrogen is supplied into the reactor. The Siemens method is a method of depositing and growing polycrystalline silicon on the surface of a silicon core wire using the CVD (Chemical Vapor Deposition) method. As an apparatus for carrying out this manufacturing method, a reactor for manufacturing polycrystalline silicon in which a large number of silicon core wires are erected in a reaction furnace is used.

[0003] Regarding the arrangement of the silicon core wire erected in the reactor, the supply port of the raw material gas, and the discharge port of the reaction gas, various aspects have been proposed in the past in consideration of reducing the surface shape defect of the generated polycrystalline silicon and manufacturing efficiency.

[0004] For example, the reactor for manufacturing polycrystalline silicon described in Patent Document 1 has a gas discharge port provided on the inner peripheral side of the furnace in order to achieve a smooth gas flow inside the furnace, while alternately arranging multiple rows of raw material gas supply nozzles and electrode holders arranged annularly along the inner periphery of the furnace.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When polycrystalline silicon is produced using a bell jar, by-products adhere to the inner wall surface of the cooled bell jar. These by-products contain chlorides, and when the bell jar is opened, they undergo hydrolysis with moisture in the atmosphere to generate hydrogen chloride, which can corrode the inner wall surface of the reactor. Furthermore, when by-products adhere to the inner wall surface of the bell jar, the reflectivity of the bell jar surface decreases. A decrease in the reflectivity of the bell jar surface reduces power efficiency and prevents the temperature inside the bell jar from rising sufficiently during polycrystalline silicon production, thus preventing the deposition of polycrystalline silicon.

[0007] The conventional techniques described above do not take into account the adhesion of by-products to the inner wall surface of the berja.

[0008] One aspect of the present invention aims to realize a polycrystalline silicon manufacturing apparatus that reduces the adhesion of by-products to the inner wall surface of the bellows. [Means for solving the problem]

[0009] To solve the above problems, a polycrystalline silicon manufacturing apparatus according to one aspect of the present invention comprises a reaction furnace whose interior is sealed by a bell jar and a disc-shaped bottom plate, the bottom plate is provided with a plurality of electrode pairs for holding a silicon core wire and energizing the silicon core wire, and a plurality of supply nozzles for supplying raw material gas to the internal space of the bell jar, the plurality of electrode pairs are arranged on n concentric circles, and in the horizontal cross-section of the bottom plate, with the center of the concentric circles being the inside and the periphery of the bottom plate being the outside, all of the supply nozzles are positioned outside the nth concentric circle from the inside. [Effects of the Invention]

[0010] According to one aspect of the present invention, the adhesion of by-products to the inner wall surface of the berja can be reduced. [Brief explanation of the drawing]

[0011] [Figure 1]This is a schematic cross-sectional view showing the configuration of a polycrystalline silicon manufacturing apparatus according to Embodiment 1 of the present invention. [Figure 2] This is a plan view showing the arrangement of electrodes, a supply nozzle, and an exhaust port on a bottom plate according to Embodiment 1 of the present invention. [Figure 3] This is a plan view showing the arrangement of electrodes, a supply nozzle, and an exhaust port on the bottom plate according to Embodiment 2 of the present invention. [Figure 4] This is a partially enlarged cross-sectional view of a plane perpendicular to the bottom plate according to Embodiment 2 of the present invention. [Figure 5] This is a plan view showing the arrangement of electrodes, supply nozzles, and exhaust ports on the bottom plate of a reactor used as a comparative example. [Figure 6] This is a schematic diagram illustrating the method for measuring the surface cone ratio. [Modes for carrying out the invention]

[0012] [Embodiment 1] (Manufacturing equipment for polycrystalline silicon) Embodiments of the present invention will be described below. The following description is intended to provide a better understanding of the invention and does not limit the present invention unless otherwise specified. Furthermore, in this specification, "A to B" indicates a range of A or greater and B or less.

[0013] First, using Figure 1, we will outline an example of a manufacturing facility for polycrystalline silicon rods used in the Siemens process. Figure 1 is a schematic cross-sectional view showing the structure of a polycrystalline silicon manufacturing apparatus (hereinafter referred to as manufacturing apparatus 100) according to one embodiment of the present invention.

[0014] As shown in Figure 1, the manufacturing apparatus 100 comprises a reactor 1 whose interior is sealed by a bell jar 3 and a disc-shaped bottom plate 2. The bottom plate 2 is provided with a plurality of electrode pairs 4 for holding a silicon core wire 10 and energizing the silicon core wire 10, a plurality of supply nozzles 6 for supplying raw material gas, and a plurality of exhaust ports 7 for exhausting exhaust gas.

[0015] Although not shown in Figure 1, the manufacturing apparatus 100 may also be equipped with a power-on system. This power-on system may, for example, include an auxiliary heater installed in the reactor 1 that can preheat the silicon core wire 10. Silicon has a property called negative resistance. That is, the electrical resistivity of silicon is high in the low temperature range and low in the high temperature range. Therefore, by providing an auxiliary heater that generates heat using single-phase AC or three-phase AC in the reactor 1, the silicon core wire 10 can be preheated by the auxiliary heater, and power can be started after the electrical resistivity has been reduced. Alternatively, the power-on system may be equipped with a power supply circuit that is capable of applying a high voltage specifically for the time of power-on. By connecting the silicon core wire 10 to this power supply circuit and starting power-on, a high voltage can be applied to the silicon core wire 10, which has high electrical resistivity, and the temperature can be raised smoothly.

[0016] In the production of the polycrystalline silicon rod 8, the raw material gas can be supplied to the internal space of the reactor 1 via a supply nozzle 6. The raw material gas is a mixed gas containing a silane compound and hydrogen. Examples of silane compounds include chlorosilane compounds such as trichlorosilane (SiHCl3) and monosilane (SiH4).

[0017] The silicon core wire 10 is processed to be in an inverted U shape, as shown in Figure 1, for example, and is installed for a pair of electrode pairs 4, and is electrically connected to the electrode pairs 4. Power is supplied to the silicon core wire 10 from the power supply unit 5 via the electrode pairs 4 and the silicon core wire 10 is heated by the current. As a result, polycrystalline silicon is deposited on the surface of the silicon core wire 10. The silicon that has been deposited and grown on the surface of the silicon core wire 10 is called a polycrystalline silicon rod 8. More specifically, the silicon core wire 10 has two columnar parts 101 and 102, and two polycrystalline silicon rods 8 are obtained as the silicon core wire 10 connected to one electrode pair 4 grows. That is, the number of polycrystalline silicon rods 8 produced in the reactor 1 is equal to the number of electrodes 41 placed on the bottom plate 2.

[0018] The bell jar 3 is a bell-shaped cover that forms part of the reactor 1. The bell jar 3 is preferably formed of a material that has good heat resistance and light weight, does not adversely affect the reaction, and can be easily cooled. For example, it is formed of stainless steel. The outer surface of the bell jar 3 may be covered with a cooling jacket. Also, for the inner wall of the bell jar 3 and other members installed in the reactor 1, depending on the installation position of the members, it is preferable to be composed of a material with a low emission of so-called impurity elements other than silicon, hydrogen, and chlorine in a temperature environment of 200 to 600 °C. Thereby, the purity of the polycrystalline silicon to be manufactured can be further improved.

[0019] The bottom plate 2 is a disk-shaped plate that forms the bottom surface of the reactor 1. The bottom plate 2 is formed, for example, of stainless steel. A plurality of electrode pairs 4 for holding the silicon core wire 10 and energizing the silicon core wire are provided on the bottom plate 2. Each electrode pair 4 is composed of two electrodes 41. The electrode 41 can be formed of carbon, SUS, Cu, or the like. In FIG. 1, only one silicon core wire 10 is shown, but usually, a plurality of silicon core wires 10 can be provided according to the volume of the reactor 1. Each of the silicon core wires 10 is connected to the electrode pair 4 and erected so that each silicon core wire 10 is energized. The arrangement of each silicon core wire 10 will be described later.

[0020] In addition, the bottom plate 2 is provided with a plurality of supply nozzles 6 and a plurality of exhaust ports 7. FIG. 2 is a plan view showing the arrangement of the electrodes 41 (electrode pair 4), supply nozzles 6 and exhaust ports 7 on the bottom plate 2. The arrangement of the electrodes 41 is, in other words, the arrangement of the silicon core wire 10 or the polycrystalline silicon rod 8. As shown in FIG. 2, in the present embodiment, the electrodes 41 are arranged on four concentric circles with different radii centered on the center of the bottom plate 2 (n = 4). In the horizontal cross section of the bottom plate 2, with the center of the concentric circles being the inner side and the periphery of the bottom plate 2 being the outer side, six electrodes 41 (three electrode pairs 4) are provided on the innermost first circle A. On the second circle B from the inside, which is located outside the circle A, twelve electrodes 41 (six electrode pairs 4) are provided. On the third circle C from the inside, which is located outside the circle B, eighteen electrodes 41 (nine electrode pairs 4) are provided. On the fourth circle D from the inside, which is located outside the circle C, twenty-four electrodes 41 (twelve electrode pairs 4) are provided.

[0021] Note that, in FIG. 2, the case where the number of concentric circles on which the electrodes 41 are arranged is four is shown, but the number of the concentric circles is not limited to four. The number of the concentric circles is usually two to seven, preferably three to five. Also, the number of the electrodes 41 arranged on each circle or the total number of the electrodes 41 arranged on the bottom plate 2 is not limited to the numbers exemplified in FIG. 2. For example, the total number of the electrodes 41 arranged on the bottom plate 2 is usually twelve to two hundred and sixteen, preferably eighteen to one hundred and forty-four, more preferably thirty-six to ninety-six.

[0022] In the manufacturing equipment of a general polycrystalline silicon rod using the Siemens method, the lower part of the reactor is in a state where power cables, electrode cooling water pipes, raw material gas pipes, exhaust gas pipes, etc. are crowded. Therefore, increasing the number of concentric circles on which the electrodes 41 are arranged can improve productivity, but when performing leak inspection or various maintenance, it becomes difficult to reach the inspection or maintenance points, and the inspection or maintenance work tends to become difficult. From the above, considering both productivity and workability, it is preferable that the number of concentric circles or the number of electrodes is within the above range.

[0023] The twelve supply nozzles 6 arranged on the bottom plate 2 are all positioned outside the fourth circle D from the inside. That is, if the electrodes 41 are arranged on n concentric circles, all the supply nozzles 6 are positioned outside the nth concentric circle. Note that the number of supply nozzles 6 arranged on the bottom plate 2 is not limited to the example shown in Figure 2 and can be arbitrarily set depending on the size of the reactor 1, etc. Furthermore, it is preferable that the supply nozzles 6 arranged on the bottom plate 2 are arranged at approximately equal intervals on a circle centered on the center of the bottom plate 2.

[0024] By positioning the supply nozzles 6 outside the electrodes 41, the adhesion or residue of by-products on the inner wall of the bell jar 3 is reduced. This reduces the amount of hydrogen chloride generated when the reactor 1 is opened and the by-products react with moisture in the atmosphere through hydrolysis, thereby reducing equipment deterioration such as corrosion of the reactor's inner wall. It also reduces the cleaning work required to remove by-products adhering to the inner wall of the reactor 1. Furthermore, by positioning all the supply nozzles 6 outside the concentric circle where the electrodes 41 are located, a workspace is secured at the bottom of the reactor 1, making it easier for workers to enter and facilitating tasks such as leak inspections. In addition, the raw material gas piping and exhaust gas piping may be branched or merged near the bottom of the reactor 1 (the underside of the bottom plate 2), and / or the electrode cooling water piping may be replaced with flexible resin tubing and bundled, thereby streamlining the piping routes. This can achieve further improvements in workability.

[0025] Furthermore, because all the supply nozzles 6 are positioned outside the electrodes 41, the resulting polycrystalline silicon rod 8 has a stable shape, being thicker towards the bottom plate 2 and tapering towards the top, i.e., having a low center of gravity. This shape is thought to be due to the following reason: The arrangement of the supply nozzles 6 creates a flow in which low-temperature raw material gas reaches the top of the bell jar 3. This cools the upper part of the silicon core wire 10, while the surface temperature of the lower part of the silicon core wire 10, through which the heated downward flow passes, becomes relatively high. When sufficient raw material is supplied, the deposition speed of polycrystalline silicon increases as the temperature of the deposition surface increases, resulting in the stable shape of the resulting polycrystalline silicon rod 8.

[0026] Furthermore, after the energization is stopped, the polycrystalline silicon rod 8 undergoes contraction equal to the thermal expansion coefficient of the material during the cooling process. On the other hand, since both ends of the polycrystalline silicon rod 8 are fixed by the electrode pair 4, thermal stress is applied mainly to the upper rectangular portion, often causing it to break. When such an event occurs, a polycrystalline silicon rod with a high center of gravity may lose its balance and collapse. The polycrystalline silicon rod produced in the reactor 1 according to this embodiment has a low center of gravity, thus reducing the risk of such collapse.

[0027] Furthermore, all 12 exhaust ports 7 provided on the bottom plate 2 are located inside the third circle C from the inside of the concentric circles on which the electrodes 41 are arranged. More specifically, as shown in Figure 2, six ports are located outside circle A and inside circle B, and six ports are located outside circle B and inside circle C. That is, if the electrodes 41 are arranged on n concentric circles, all exhaust ports 7 are located inside the (n-1)th concentric circle. Note that the number of exhaust ports 7 on the bottom plate 2 is not limited to the example shown in Figure 2 and can be arbitrarily set depending on the size of the reactor 1, etc. It is also preferable that the exhaust ports 7 on the bottom plate 2 are provided on multiple concentric circles centered on the center of the bottom plate 2 and are arranged at approximately equal intervals in each concentric circle.

[0028] If the supply nozzle 6 is provided only on the outermost periphery, the supply of raw material to the silicon core wires 10 located further inside may be insufficient. By arranging the exhaust port 7 as described above, the supply of raw material to the silicon core wires 10 located further inside can be promoted, and variations in raw material supply between the silicon core wires 10 can be reduced.

[0029] The reaction conditions, such as the pressure inside reactor 1 and the piping communicating with reactor 1, the mixing ratio and supply amount of the silane compound and hydrogen, and the surface temperature of the silicon core wire 10, can be used with virtually no limitations, as long as the necessary design requirements are met, in accordance with the disclosed prior art.

[0030] The pressure inside reactor 1 is preferably set to atmospheric pressure to 1000 kPaG, more preferably 100 to 600 kPaG, based on design requirements that consider the balance of piping dimensions, strength, and cooling efficiency corresponding to the gas supply rate. The mixing ratio of silane compound and hydrogen in the raw material gas is preferably such that the silane compound does not liquefy in the raw material gas piping, bell jar, and exhaust gas piping under their respective pressure and temperature environments, and that a sufficient amount of silane compound raw material for the reaction can be supplied within the limited piping volume. For example, the molar ratio of silane compound to hydrogen may be 3 to 15, more preferably 3 to 9, relative to 1 silane compound.

[0031] The temperature of the raw material gas supplied from the supply nozzle 6 can be between 0 and 150°C, from the viewpoint of reducing the possibility of liquefaction of the silane compound and suppressing the enlargement of the raw material piping due to heat retention. However, in order to obtain the effect of forming the aforementioned stable-shaped rod, the temperature of the raw material gas is preferably between 0 and 60°C.

[0032] The surface temperature of the silicon core wire 10 is preferably such that an industrially viable silicon deposition rate can be obtained without the silicon melting. The surface temperature of the silicon core wire 10 is, for example, 800 to 1410°C, and preferably 900 to 1150°C to suppress local temperature deviations and reduce the formation of popcorn, as described later. As for the conditions regarding the raw material supply, it is generally the case that a silane compound containing 5 to 100 times the number of silicon atoms deposited on the silicon core wire 10 per unit time can always be supplied. It will be easily understood by those skilled in the art that the fluctuation in the amount of polycrystalline silicon produced due to the change in surface temperature mentioned above should be taken into consideration when determining the raw material supply.

[0033] (Embodiment 2) Other embodiments of the present invention will be described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0034] During the growth process of the polycrystalline silicon rod 8, if the raw material gas is not stably supplied to the surface of each silicon core wire 10, irregularities (also called popcorn) may occur on the surface of the silicon rod. When popcorn occurs, the current path changes, causing an imbalance in the current and resulting in locally high-temperature areas, which may cause partial melting on the surface of the silicon rod. In addition, closed pores may be formed as polycrystalline silicon precipitates on the depressions of the popcorn. Thus, the occurrence of popcorn may cause shape defects in the polycrystalline silicon rod 8. Therefore, it is preferable to supply the raw material gas in a way that can reduce the occurrence of popcorn.

[0035] As a result of diligent research, the inventors found that by making the gas ejection direction of the supply nozzle 6 inclined toward the inner wall of the bell jar 3, that is, radially outward toward the bottom plate 2, the surface cone ratio of the generated polycrystalline silicon rod 8 can be reduced. The surface cone ratio is an indicator of the proportion of the popcorn generation area on the surface of the polycrystalline silicon rod 8, and the calculation method will be described later.

[0036] Figure 3 is a plan view showing the arrangement of the electrodes 41, the supply nozzle 6A, and the exhaust port 7 on the bottom plate 2A of the reactor 1A according to Embodiment 2. The reactor 1A according to Embodiment 2 is equipped with an inclined supply nozzle 6A. Except for the fact that the supply nozzle 6A is inclined, the reactor 1A has the same configuration as the reactor 1 according to Embodiment 1. The arrows shown in Figure 3 indicate the inclination direction of each supply nozzle 6A.

[0037] Figure 4 is a partially enlarged cross-sectional view of the bottom plate 2A of the reactor 1A in a plane perpendicular to it. Figure 4 shows an example in which the supply nozzle 6A is inclined toward the inner wall of the bell jar 3, i.e., radially outward from the bottom plate 2A, and as a result, its gas ejection direction is inclined in the same direction. In other words, the gas ejection direction of the raw material gas ejected from the supply nozzle 6A is inclined toward the inner wall of the bell jar 3. The inclination of the gas ejection direction of the supply nozzle 6A is such that the angle θ (see Figure 3) between the line extending the raw material gas ejection direction of the supply nozzle 6A and the inner wall of the bell jar 3 is 12° or less, preferably 2.5 to 8°. Also, the distance L (m) of the raw material gas path from the end of the supply nozzle 6A to the inner wall of the bell jar 3 is 1 / 40th or less of the raw material gas supply velocity (m / s) at that end, preferably 1 / 100th to 1 / 50th.

[0038] The raw material gas path is a typical path for the raw material gas, and is a path along a line extending from the direction of raw material gas ejection. The raw material gas path is shown as a dashed line in Figure 4. In actual equipment configurations, the supply nozzle 6A may include an internal flow path (piping) of the base plate 2A and a nozzle portion protruding from the base plate 2A. As shown in Figure 4, the internal flow path of the base plate 2A and the supply nozzle 6A may be inclined at an angle θ with respect to the vertical. Alternatively, the internal flow path of the base plate 2A may be formed in the vertical direction, and a joint including a path inclined at an angle θ with respect to the vertical may be attached to the upper end of the internal flow path. Regardless of which of the above configurations is adopted, the ejection direction of the raw material gas ejected from the supply nozzle 6A may be inclined at an angle θ with respect to the vertical.

[0039] The length of the supply nozzle 6A can be appropriately determined, taking into consideration the purpose of ensuring stability in the direction of gas ejection and adjusting the distance L of the raw material gas path to the inner wall of the bell jar 3. If the inclination of the internal flow path of the bottom plate 2A forms an angle θ with respect to the inner wall of the bell jar, the supply nozzle 6A does not need to protrude from the bottom plate 2A. When adjusting the angle θ of the nozzle portion that protrudes onto the bottom plate 2A, the length of the nozzle portion can be set to a range that does not exceed approximately 600 mm. If the length of the nozzle portion exceeds 600 mm, the strength against gas flow in the reactor may be insufficient, and it may become necessary to increase the wall thickness to avoid insufficient strength, which is undesirable from a design perspective.

[0040] The number and inner diameter of the supply nozzles 6A can be appropriately determined considering the distance L of the raw material gas path and the supply rate. To reduce the adhesion of by-products to the inner wall of the bell jar 3, it is preferable that the reactor 1 be equipped with six or more supply nozzles 6A. Furthermore, from the viewpoint of avoiding excessive complexity of the piping layout below the bottom plate 2A, it is preferable that the number of supply nozzles 6A be 24 or less. The inner diameter of the supply nozzles 6A can be limited to some extent by selecting the various conditions described above, and may be, for example, 6 to 30 mm.

[0041] By adjusting the inclination angle of the supply nozzle and the supply rate of the raw material gas so that the angle θ is 12° or less and the distance L is 1 / 40th or less of the initial velocity of the raw material gas, the raw material gas approaches the inner wall via a shorter path compared to when the supply nozzle is positioned vertically on the bottom plate, thus reducing the kinetic energy lost before reaching the inner wall. Furthermore, because the collision occurs at a small angle of 12° or less, an upward flow with reduced kinetic energy loss can be created. The upward flow close to the inner wall is less affected by turbulence within the reactor, allowing it to reach the top of the reactor with relatively little loss of kinetic energy. In addition, by keeping the upward flow away from the silicon core wire 10, oscillations caused by the upward flow and subsequent collapse due to repeated oscillations can be avoided, thus increasing the initial velocity itself. The raw material gas, which maintains its kinetic energy, can maintain its velocity even when it becomes a downward flow descending from the top to the bottom of the reactor 1. As a result, the raw material gas is efficiently supplied to the lower part of the polycrystalline silicon rod 8 where popcorn is likely to form, and the surface cone ratio can be reduced.

[0042] With the above configuration, the manufacturing apparatus equipped with the reactor 1A according to Embodiment 2 reduces the adhesion or residue of by-products to the inner wall of the bell jar 3. Furthermore, the resulting polycrystalline silicon rod 8 has a stable shape that is thicker at the bottom plate 2 side and becomes thinner towards the top. In addition, the surface cone ratio of the generated polycrystalline silicon rod 8 can be reduced.

[0043] [Additional Notes] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0044] [Demonstration Test] The following describes demonstration tests using a reactor according to the above embodiment as an example and a reactor outside the scope of the present invention as a comparative example. In the following comparative example and example, a mixed gas containing hydrogen and trichlorosilane was used as the raw material gas. The molar ratio of trichlorosilane to hydrogen in the mixed gas was 1:7.5. The pressure inside each reactor during operation was 130 kPaG. The increase patterns of the control current and raw material gas flow rate with increasing deposition diameter were kept the same.

[0045] Figure 5 is a plan view showing the arrangement of electrodes 41, supply nozzles 6, and exhaust ports 7 on the bottom plate 2B of reactor 1B used as a comparative example. The arrangement of electrodes 41 on the bottom plate 2B is the same as that of the bottom plate 2 of Embodiment 1, with n=4 being the number of concentric circles on which electrodes 41 are arranged. All of the supply nozzles 6 on the bottom plate 2B are located inside the outermost concentric circle (circle D) on which electrodes 41 are arranged. More specifically, the supply nozzles 6A are located on concentric circles centered on the center of the bottom plate 2B, between circle A and circle B, between circle B and circle C, or between circle C and circle D. The exhaust ports 7 are located on the same concentric circles as the supply nozzles 6A. In other words, reactor 1B of the comparative example has a configuration outside the scope of the present invention. The inner diameter of the supply nozzles 6 in reactor 1B of the comparative example is 13.7 mm, and the supply rate of raw material gas at the end of the supply nozzles 6 was 88.1 m / s.

[0046] For Example 1, the reactor 1 of Embodiment 1 described above was used. The inner diameter of the supply nozzle 6 provided in the reactor 1 was 27 mm, and the supply rate of the raw material gas at the end of the supply nozzle 6 was 88.3 m / s.

[0047] For Example 2, the reactor 1A of Embodiment 2 described above was used. The inner diameter of the supply nozzle 6A provided in reactor 1A was 18.7 mm, and the supply rate of the raw material gas at the end of the supply nozzle 6A was 176.5 m / s. The inclination angle of the supply nozzle 6A of reactor 1A used in Example 2 was 4° radially outward from the vertical direction of the bottom plate 2B. That is, the angle θ was 4°. In the demonstration test, the amount of residue recovered due to by-products adhering to the inner wall of each reactor, surface cone ratio, and rod shape were measured for the Comparative Example, Example 1, and Example 2. Table 1 is a table summarizing the test results for the Comparative Example, Example 1, and Example 2.

[0048] [Table 1] (Amount of reactor residue recovered) After opening each reactor, all by-products adhering to the inner walls of the bergers containing chlorides were recovered as oxide residues using hot water or steam. The recovered residues were dehydrated and weighed. The results are shown in Table 1. The numbers in parentheses in Table 1 indicate the recovery amount (%) relative to the comparative example (set as 100%).

[0049] As shown in Table 1, the amount of residue recovered in Examples 1 and 2 was significantly reduced compared to the comparative example. In other words, it was demonstrated that by using a manufacturing apparatus within the scope of the present invention, the adhesion of by-products to the inner wall of the bell jar is significantly reduced.

[0050] (Surface cone ratio) Figure 6 is a schematic diagram illustrating the method for measuring the surface cone ratio. The surface cone ratio was measured as follows. First, as shown by reference numeral 601 in Figure 6, the polycrystalline silicon rod 8 was divided vertically at intervals of 100 mm. The upper part of the polycrystalline silicon rod 8, including the U-shaped curved section, was divided into three sections as shown by reference numeral 601. Reference numeral 602 in Figure 6 is an enlarged view showing one of the divided pieces. Next, each piece divided at 100 mm intervals was further divided into approximately four equal parts. These four divided pieces are referred to as nuggets 81. For each nugget 81, it was determined whether popcorn had formed or if the surface was smooth by visually inspecting the central region R of the surface corresponding to the rod surface. In this determination, a nugget 81 was judged to have popcorn if the shadows caused by the steps formed a mesh pattern under typical indoor lighting of 300 to 500 lux. If a nugget 81 with popcorn formed is called a nugget P, the surface cone ratio can be calculated by dividing the number of nuggets P by the total number of nuggets.

[0051] As shown in Table 1, the high surface cone ratio in Example 1 is significantly reduced in Example 2. In other words, it has been demonstrated that the surface cone ratio can be reduced by tilting the supply nozzle.

[0052] (Rod shape) As values ​​indicating the shape of the generated polycrystalline silicon rod 8, the diameter at a position 400 mm from the top end (referred to as diameter T) and the diameter at a position 400 mm from the bottom end (referred to as diameter B) were measured for the polycrystalline silicon rod 8. In the results shown in Table 1, the numerator is diameter T and the denominator is diameter B.

[0053] As shown in Table 1, in the comparative example, the diameter T and diameter B are approximately equal, and a polycrystalline silicon rod 8 with a nearly uniform thickness from the top to the bottom is obtained. On the other hand, in Examples 1 and 2, the diameter B is larger than the diameter T, and the shape of the polycrystalline silicon rod 8 is thicker from the top to the bottom. In other words, it has been demonstrated that a polycrystalline silicon rod 8 with a stable shape can be obtained in Examples 1 and 2. [Explanation of Symbols]

[0054] 1, 1A... Reactor 2, 2A...Bottom plate 3. Berja 4. Electrode pairs 6, 6A... Supply nozzle 7. Exhaust port 8. Polycrystalline silicon rods 10. Silicone core wire 100...Manufacturing equipment

Claims

1. a reactor whose interior is sealed by a bell jar and a disk-shaped bottom plate; the bottom plate is provided with a plurality of electrode pairs for holding silicon core wires and applying current to the silicon core wires, and a plurality of supply nozzles for supplying a source gas into the internal space of the bell jar; the plurality of electrode pairs are arranged on n concentric circles, in a horizontal cross section of the bottom plate, when the centers of the concentric circles are defined as the inside and the periphery of the bottom plate is defined as the outside, all of the supply nozzles are positioned outside an n-th concentric circle from the inside.

2. 2. The manufacturing apparatus according to claim 1, wherein the bottom plate is provided with a plurality of exhaust ports for exhausting gas from the internal space of the bell jar, and all of the exhaust ports are arranged inside the (n-1)th concentric circle.

3. 3. The manufacturing apparatus according to claim 1, wherein the source gas is ejected from the supply nozzle disposed outside the n-th concentric circle in a direction inclined toward the inner wall of the bell jar.

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