Polycrystalline-silicon manufacturing device

Abstract

The present invention is for efficiently manufacturing polycrystalline-silicon and reducing unevenness arising on the surface of the polycrystalline-silicon. A manufacturing device (1) comprises: a reaction furnace (10); and a plurality of supply nozzles (40) having formed therein supply ports (41) for supplying a raw material gas (G1) to a space (SP) inside the reaction furnace (10). A first distance (L1) along the vertical direction between the supply ports (41) of the supply nozzles (40) and an upper end (31) of a core-wire holding part (30) is 100-500 mm.

Description

Manufacturing Apparatus for Polycrystalline Silicon 【0001】 The present invention relates to a manufacturing apparatus for polycrystalline silicon. 【0002】 Conventionally, it has been required to efficiently manufacture polycrystalline silicon using a reactor whose interior is sealed by a bell jar and a bottom plate. Therefore, in order to efficiently manufacture polycrystalline silicon by heating the interior space of the reactor to a high temperature, as described in Patent Document 1 and Patent Document 2, it is conceivable to use a reactor whose inner wall of the bell jar is made of silver, tungsten, gold or platinum. 【0003】 Japanese Patent Application Laid-Open No. 55-095319, Japanese Patent Application Laid-Open No. 01-208312 【0004】 However, in the technologies described in Patent Document 1 and Patent Document 2, since the temperature in the vicinity of the upper part of the polycrystalline silicon deposited inside the reactor tends to be particularly high, there is a problem that unevenness called cones is likely to occur on the surface in the vicinity of the upper part of the polycrystalline silicon. 【0005】 One aspect of the present invention aims to efficiently manufacture polycrystalline silicon while reducing unevenness generated on the surface of the polycrystalline silicon. 【0006】 In order to solve the above problems, a manufacturing apparatus for polycrystalline silicon according to one aspect of the present invention includes a bell jar having an inner wall made of a material with an emissivity of 0.1 or less before polycrystalline silicon is deposited, a bottom plate, a reactor whose interior is sealed by them, a silicon core wire for depositing polycrystalline silicon, a core wire holding part for holding the silicon core wire inside the reactor, and a plurality of supply nozzles provided on the bottom plate and having supply ports formed in the space inside the reactor for supplying a raw material gas. When a direction perpendicular to the bottom plate is defined as the vertical direction, a first distance along the vertical direction between the supply port of at least one of the plurality of supply nozzles and the upper end of the core wire holding part is 100 mm or more and 500 mm or less. 【0007】 According to one aspect of the present invention, it is possible to efficiently manufacture polycrystalline silicon while reducing unevenness generated on the surface of the polycrystalline silicon. 【0008】 This is a cross-sectional view showing an example of the configuration of a polycrystalline silicon manufacturing apparatus according to an embodiment of the present invention. This is a diagram illustrating the relationship between a first distance and a second distance in the polycrystalline silicon manufacturing apparatus shown in Figure 1. This is a diagram illustrating the positions of the supply ports of a plurality of supply nozzles in the polycrystalline silicon manufacturing apparatus shown in Figure 1. This is a diagram showing polycrystalline silicon with no surface irregularities and polycrystalline silicon with surface irregularities. This is a diagram illustrating the surface cone ratio measurement method shown in Table 1. 【0009】 <Configuration of Polycrystalline Silicon SL Manufacturing Apparatus 1> Figure 1 is a cross-sectional view showing an example of the configuration of a polycrystalline silicon SL manufacturing apparatus 1 according to an embodiment of the present invention. In Figure 1, the direction from the electrode 50 toward the silicon core wire 20 is defined as the positive Z-axis direction, and the plane perpendicular to the Z-axis direction is defined as the XY plane. The manufacturing apparatus 1 is an apparatus for manufacturing a polycrystalline silicon rod by depositing polycrystalline silicon SL onto the silicon core wire 20. 【0010】 As shown in Figure 1, the manufacturing apparatus 1 comprises a reaction furnace 10, a silicon core wire 20, a core wire holder 30, a plurality of supply nozzles 40, and electrodes 50. Although Figure 1 shows the case where there is one silicon core wire 20, the manufacturing apparatus 1 may have a plurality of silicon core wires 20. Also, although Figure 1 shows the case where there are two core wire holders 30 and two electrodes 50, the manufacturing apparatus 1 may have three or more core wire holders 30 and three or more electrodes 50. 【0011】 <Configuration of the reactor 10> The reactor 10 has a bell jar 11 and a disc-shaped bottom plate 12, and houses a silicon core wire 20, a core wire holder 30, a plurality of supply nozzles 40, and electrodes 50. The inside of the reactor 10 is sealed by the bell jar 11 and the bottom plate 12. 【0012】The bell jar 11 has an inner wall 111 made of a material whose emissivity is 0.1 or less before polycrystalline silicon SL is deposited on the silicon core wire 20. Specifically, it is preferable that the surface of the inner wall 111 of the bell jar 11 is made of silver. The entire inner wall 111 may be formed of the same material, but in order to ensure strength that can withstand the pressure inside the reaction furnace 10 during polycrystalline silicon production, the bell jar 11 may be made of a common structural material such as SUS or cast iron, and a layer of material with an emissivity of 0.1 or less may be formed in close contact with its inner wall 111. 【0013】 In this case, the thickness of the material layer with an emissivity of 0.1 or less is generally 0.05 mm to 5 mm, and known joining techniques such as pressure welding, explosive bonding, welding, thermal spraying, or plating can be used as bonding methods. The emissivity before the deposition of polycrystalline silicon SL can be rephrased as the emissivity of the surface of the inner wall 111 when no reactants produced by the reaction in the reactor 10 are adhering to the inner wall 111. 【0014】 Furthermore, the surface roughness Ra of the inner wall 111 is preferably 0.400 μm or less. The reaction material adhering to the inner wall 111 is generally removed by physical methods such as air blowing, water washing, or wiping when the bell 11 is lifted and the polycrystalline silicon SL and silicon core wire 20 on the bottom plate 12 are replaced. The removal of the reaction material is carried out with an intensity that does not significantly increase the surface roughness of the inner wall 111. 【0015】 As a result, when polycrystalline silicon SL is repeatedly produced using the reactor 10, the emissivity of the inner wall 111 of the bell jar 11 can be maintained at 0.1 or less, and the temperature of the space SP inside the reactor 10 can be maintained at a temperature suitable for the deposition of polycrystalline silicon SL. Therefore, polycrystalline silicon SL can be deposited efficiently. If the bell jar 11 is provided with a window (not shown), the surface of the part of the inner wall 111 excluding the window is made of a material with an emissivity of 0.1 or less. 【0016】<Method for Measuring Emissivity> The emissivity of the material on the surface of the inner wall 111 is measured by the method described below. The sample to be measured for emissivity is left at room temperature for about one hour to allow the sample temperature to stabilize sufficiently. The measuring part of the measuring device (product name: TSS-5X-3, manufactured by Japan Sensor Co., Ltd.) is placed against two types of reference pieces (emissivity 0.06 and 0.97) attached to the measuring device, and the value of the detection part of the measuring device is calibrated by setting the value of the detection part of the measuring device to the emissivity of the reference piece using the adjustment dial. After the calibration of the value of the measuring part is completed, the measuring part of the measuring device is placed against the inner wall 111, and the emissivity of the material on the surface of the inner wall 111 is measured. 【0017】 <Configuration of Silicon Core Wire 20 and Core Wire Holding Part 30> The silicon core wire 20 is for depositing polycrystalline silicon SL. The silicon core wire 20 has a U-shape and is electrically connected to a pair of electrodes 50 via the core wire holding part 30. The core wire holding part 30 holds the silicon core wire 20 inside the reactor 10. A portion of the core wire holding part 30 on the positive Z-axis side becomes embedded in the polycrystalline silicon SL as it is deposited on the silicon core wire 20. 【0018】 The core wire holding portion 30 holds the silicon core wire 20, thereby holding the polycrystalline silicon SL deposited on the silicon core wire 20. The core wire holding portion 30 is provided so as to cover the lower end 21 of the silicon core wire 20. 【0019】 <Configuration of the supply nozzles 40> The multiple supply nozzles 40 are for supplying raw material gas G1 to the space SP inside the reactor 10. The raw material gas G1 is, for example, a mixture of hydrogen and trichlorosilane, or a mixture of hydrogen, dichlorosilane, and trichlorosilane. The multiple supply nozzles 40 are provided on the bottom plate 12 and extend from the bottom plate 12 in the positive Z-axis direction. A supply port 41 is formed at the Z-axis positive end of each of the multiple supply nozzles 40 for supplying raw material gas G1 to the space SP inside the reactor 10. 【0020】Furthermore, the ends of each of the multiple supply nozzles 40 on the negative Z-axis side are connected to through holes 121 formed in the bottom plate 12. A gas supply unit (not shown) located outside the reactor 10 supplies raw material gas G1 to each of the multiple supply nozzles 40 via the through holes 121. The raw material gas G1 is supplied into the reactor 10 from the supply ports 41 of each of the multiple supply nozzles 40. 【0021】 Furthermore, it is preferable that the supply ports 41 of all supply nozzles 40 provided on the bottom plate 12 be positioned at or above the upper end 31 of the core wire holding portion 30. In other words, it is preferable that the first distance L1, described later, is 0 mm or more for the supply ports 41 of all supply nozzles 40. 【0022】 Preferably, the upper part of the supply nozzle 40, particularly the end on the positive Z-axis side, is made of quartz. This prevents impurities from being generated from the supply nozzle 40 in the high-temperature environment above the space SP inside the reactor 10, thereby preventing contamination of the polycrystalline silicon SL. Furthermore, the flow rate of the raw material gas G1 supplied from each supply nozzle 40 may be approximately uniform across all supply nozzles 40, or it may be biased. Note that the flow rate of the raw material gas G1 may differ for each supply nozzle 40. 【0023】 <Configuration of Electrode 50> The electrode 50 is for conducting current to the silicon core wire 20 and is provided on the bottom plate 12. An insulating member (not shown) is provided between the electrode 50 and the bottom plate 12 to prevent current from flowing from the electrode 50 to the bottom plate 12. The material of the electrode 50 is, for example, a carbon material or a metal material such as SUS. 【0024】 <Regarding the first distance L1> The vertical direction is defined as the direction perpendicular to the Z-axis, that is, the direction perpendicular to the bottom plate 12. In this case, the first distance L1 along the vertical direction between the supply port 41 of at least one of the multiple supply nozzles 40 and the upper end 31 of the core wire holding part 30 is 100 mm or more and 500 mm or less. It is more preferable that the first distance L1 is 100 mm or more and 400 mm or less. The position of the supply port 41 is higher than the position of the upper end 31, and the first distance L1 is expressed as a value with the positive Z-axis direction as the positive direction. 【0025】 Here, we consider the case where polycrystalline silicon SL is produced using a reactor 10 whose interior is sealed by a bell jar 11 having an inner wall 111 made of a material with an emissivity of 0.1 or less, and a bottom plate 12. In this case, the temperature near the top of the polycrystalline silicon SL deposited inside the reactor 10 tends to become particularly high. 【0026】 Specifically, radiant energy from infrared light is emitted from the polycrystalline silicon SL toward the inner wall 111 of the bell jar 11. The infrared light is then reflected by the inner wall 111, and the polycrystalline silicon SL receives radiant energy from this reflection. The upper part of the polycrystalline silicon SL receives energy reflected from the ceiling portion 112 of the bell jar 11, compared to other parts of the polycrystalline silicon SL, so the temperature in the upper part of the polycrystalline silicon SL tends to be particularly high. In addition, if the bottom plate 12 has through-holes 121 through which the raw material gas G1 passes, as well as other through-holes (not shown) to allow the reacted exhaust gas to pass through, the ventilation efficiency in the upper part of the manufacturing apparatus 1 becomes relatively lower than that in the lower part. Therefore, the low cooling effect of the raw material gas G1 on the polycrystalline silicon SL also tends to contribute to the high temperature in the upper part of the polycrystalline silicon SL. 【0027】 Therefore, it is preferable that the first vertical distance L1 between the supply port 41 of at least one supply nozzle 40 and the upper end 31 of the core wire holding portion 30 is 100 mm or more. This makes it possible to supply unreacted raw material gas G1, which is at a lower temperature than the space SP inside the reactor 10, to the space SP above. 【0028】 Therefore, the temperature can be made uniform in the space SP inside the reactor 10, and the diameter of the polycrystalline silicon SL can be made uniform, so that the polycrystalline silicon SL can be uniformly deposited on the silicon core wire 20. Consequently, the surface irregularities that occur near the top of the polycrystalline silicon SL can be reduced. 【0029】Furthermore, by ensuring that the first vertical distance L1 between the supply port 41 of at least one supply nozzle 40 and the upper end 31 of the core wire holding portion 30 is 500 mm or less, it is possible to prevent the raw material gas G1 from strongly hitting the ceiling portion 112 of the bell jar 11. This prevents the ceiling portion 112 of the bell jar 11 from being overheated by the raw material gas G1, thereby preventing the ceiling portion 112 of the bell jar 11 from degrading due to thermal deformation. In addition, the temperature of the space SP inside the reactor 10 can be maintained at a temperature suitable for the deposition of polycrystalline silicon SL. 【0030】 When the surface of the inner wall 111 of the bell 11 is made of silver, the temperature near the top of the polycrystalline silicon SL tends to be higher compared to when the surface of the inner wall 111 is made of SUS, and irregularities tend to occur on the surface near the top of the polycrystalline silicon SL. For this reason, the effect of the first distance L1 being 100 mm or more and 500 mm or less is particularly pronounced when the surface of the inner wall 111 is made of silver. 【0031】 <Regarding the second distance L2> The second distance L2 along the vertical direction between the upper end 22 of the silicon core wire 20 and the upper end 31 of the core wire holding portion 30 is preferably 2000 mm or more and 2400 mm or less. As a result of diligent research by the inventors, it was found that the appropriate distance for the second distance L2 is 2000 mm or more and 2400 mm or less. This makes it possible to supply the raw material gas G1 to the space SP inside the reactor 10 while preventing the raw material gas G1 from strongly hitting the ceiling portion 112 of the bell jar 11. 【0032】 <Relationship between the first distance L1 and the second distance L2> Figure 2 is a diagram illustrating the relationship between the first distance L1 and the second distance L2 in the polycrystalline silicon SL manufacturing apparatus 1 shown in Figure 1. As shown in Figure 2, it is preferable that the first distance L1 is 1 / 4 or less of the second distance L2. Specifically, it is preferable that the supply port 41 of at least one supply nozzle 40 is located in the lower 1 / 4 of the range obtained by dividing the second distance L2 into four equal parts. 【0033】As a result of diligent research by the inventors, it was found that the optimal distance for the first distance L1 is 1 / 4 or less of the second distance L2. This makes it possible to prevent the raw material gas G1 from strongly hitting the ceiling portion 112 of the bell jar 11. 【0034】 <L1 and L2 when the height of the upper end of the core wire holder and the length of the core wire are different> In addition, it is conceivable that the length of the multiple silicon core wires 20 erected in the polycrystalline silicon SL reaction furnace 10 and the height of the core wire holder 30 may be individually differentiated. In these cases as well, it is preferable to use the upper end 31 of the core wire holder 30 with the highest height as the reference height, and to apply the distance along the vertical direction between this reference height and the upper end 22 of the silicon core wire 20 that is at the highest point in the reaction furnace 10 as the second distance L2. 【0035】 <Position of supply ports 41 of multiple supply nozzles 40> Figure 3 is a diagram illustrating the positions of the supply ports 41 of multiple supply nozzles 40 in the polycrystalline silicon SL manufacturing apparatus 1 shown in Figure 1. In Figure 3, the core wire holding section 30 is shown as a circle, and the supply nozzles 40 are shown as triangles. Also, in Figure 3, the bell ja 11, silicon core wire 20, electrode 50, and polycrystalline silicon SL are omitted. 【0036】 As shown in Figure 3, the multiple supply nozzles 40 are arranged along multiple concentric circles C1, C2, and C3 centered on the central point CT of the base plate 12 when viewed from the vertical. Figure 3 shows the case where there are three concentric circles on which the supply nozzles 40 are arranged, but the number of concentric circles is not limited to three, and there may be three or more concentric circles. 【0037】Here, in Examples 1 to 5 and Comparative Examples 1 to 3, as shown in Figure 3, polycrystalline silicon SL was deposited on the bottom plate 12 with multiple core wire holders 30 and multiple supply nozzles 40 arranged on the bottom plate 12, and the results of depositing polycrystalline silicon SL to achieve approximately the same power consumption are shown in Table 1 below. Power consumption [kWh / kg] is the power consumption per 1 kg of polycrystalline silicon SL, and is calculated by dividing the power consumed in one polycrystalline silicon manufacturing operation by the weight obtained by subtracting the weight of the silicon core wire 20 from the total weight of polycrystalline silicon SL removed from the manufacturing apparatus 1 after the operation. For the purposes of explanation, the symbols attached to the components shown in Figure 1 are used for Examples 1 to 5 and Comparative Examples 1 to 3. 【0038】 In Table 1, the first distance L1 [mm] is the vertical distance between the supply port 41 of the supply nozzle 40 and the upper end 31 of the core wire holding part 30. The surface cone ratio [%] is an index value related to the percentage of the surface area of ​​the polycrystalline silicon SL where irregularities (also called cones or popcorns) occur, and the calculation method will be described later. 【0039】 In Table 1, the values ​​shown in the row of supply nozzles 40 provided along concentric circle C1 represent the first vertical distance L1 between the supply port 41 of the supply nozzle 40 provided along concentric circle C1 and the upper end 31 of the core wire holding portion 30. Similarly, the values ​​shown in the row of supply nozzles 40 provided along concentric circle C2 represent the first vertical distance L1 between the supply port 41 of the supply nozzle 40 provided along concentric circle C2 and the upper end 31 of the core wire holding portion 30. 【0040】 Furthermore, the value indicated by the row of supply nozzles 40 arranged along the concentric circle C3 is the first vertical distance L1 between the supply port 41 of the supply nozzle 40 arranged along the concentric circle C3 and the upper end 31 of the core wire holding portion 30. In Comparative Example 3, -300 mm indicates that the position of the supply port 41 of the supply nozzle 40 is shifted by 300 mm in the negative Z-axis direction from the upper end 31 of the core wire holding portion 30. 【0041】In Examples 1 to 5 and Comparative Examples 1 to 3 shown in Table 1, the second distance L2 was set to 2300 mm. As shown in Table 1, in Examples 1, 3 to 5, the first distance L1 in the supply nozzle 40 provided along the concentric circle C2 is longer than the first distance L1 in the supply nozzle 40 provided along the concentric circle C1. The supply port 41 is located in the lower 1 / 4 range of the range obtained by dividing the second distance L2 into four equal parts. Thereby, in Examples 1, 3 to 5, the surface cone rate could be reduced as compared with Example 2 and Comparative Examples 1 and 2. Further, in Example 2, since the first distance L1 in all the supply nozzles 40 is 280 mm, the surface cone rate could be reduced as compared with Comparative Examples 1 and 2. 【0042】 <Comparative Example 2> In Comparative Example 2, the upper part of the polycrystalline silicon SL was 2% to 15% thinner than the lower part of the polycrystalline silicon SL. When the first distance L1 is too long, that is, when the position of the supply port 41 of the supply nozzle 40 is too high as in Comparative Example 2, the temperature distribution inside the reactor 10 becomes non-uniform. Therefore, the surface cone rate of Comparative Example 2 increased by 10% or more compared to the surface cone rates of Examples 1 to 5. 【0043】 Further, in Comparative Example 2, since the upper part of the polycrystalline silicon SL was cooled too much, an appropriate temperature for the precipitation of the polycrystalline silicon SL could not be maintained, and the power efficiency of the manufacturing apparatus 1 decreased. Furthermore, when the power was increased to improve the efficiency of the precipitation of the polycrystalline silicon SL, the unevenness increased in the lower part of the polycrystalline silicon SL. Moreover, the raw material gas G1 heated to a high temperature hit the ceiling portion 112 of the bell jar 11, and the ceiling portion 112 was damaged. 【0044】 <Comparative Example 3> In Comparative Example 3, since the polycrystalline silicon SL collapsed at the time when 10% to 30% of the scheduled time required for the precipitation of the polycrystalline silicon SL had elapsed after the start of the supply of the raw material gas G1, the manufacturing apparatus 1 was stopped halfway. Specifically, at the time when 10% to 30% of the scheduled time had elapsed, the polycrystalline silicon SL could not withstand the wind pressure of the raw material gas G1 and collapsed. 【0045】In addition, due to the excessive cooling of the lower part of the polycrystalline silicon SL, the boundary between the silicon core wire 20 and the core wire holding part 30 was an environment where the precipitation of the polycrystalline silicon SL was difficult to progress. As a result, the polycrystalline silicon SL could not be stably precipitated. 【0046】 <Position of the supply port 41 in the concentric circles C1 to C3> As in Examples 1 and 3 to 5, the position of the supply port 41 of the supply nozzle 40 provided along the concentric circle C1 and the position of the supply port 41 of the supply nozzle 40 provided along the concentric circle C2 may be shifted from each other in the vertical direction. Also, as in Examples 3 to 5, the position of the supply port 41 of the supply nozzle 40 provided along the concentric circle C2 and the position of the supply port 41 of the supply nozzle 40 provided along the concentric circle C3 may be shifted from each other in the vertical direction. 【0047】 That is, when any two adjacent concentric circles among the plurality of concentric circles are taken as the first concentric circle and the second concentric circle, it is preferable that the position of the supply port 41 of the supply nozzle 40 provided along the first concentric circle and the position of the supply port 41 of the supply nozzle 40 provided along the second concentric circle are shifted from each other in the vertical direction. Thereby, between any two adjacent first concentric circle and second concentric circle, the position of the supply port 41 of the supply nozzle 40 is shifted in the vertical direction, so that the flow of the raw material gas G1 in the space SP related to the inside of the reactor 10 can be optimized. 【0048】 In the above, for example, there are cases where the first concentric circle is the concentric circle C1 and the second concentric circle is the concentric circle C2, and where the first concentric circle is the concentric circle C2 and the second concentric circle is the concentric circle C3. 【0049】 Furthermore, as in Examples 1 and 3 to 5, the supply port 41 of the supply nozzle 40 provided along the concentric circle C2 may be at a position higher than the supply port 41 of the supply nozzle 40 provided along the concentric circle C1. Also, the supply port 41 of the supply nozzle 40 provided along the concentric circle C3 may be at a position higher than the supply port 41 of the supply nozzle 40 provided along the concentric circle C2. 【0050】In other words, when viewed from a vertical direction, with the center CT of the base plate 12 being the inside and the periphery 122 of the base plate 12 being the outside, if the second concentric circle is outside the first concentric circle, then it is preferable that the supply port 41 of the supply nozzle 40 provided along the second concentric circle is at a higher position than the supply port 41 of the supply nozzle 40 provided along the first concentric circle. 【0051】 For any adjacent first and second concentric circles, the supply port 41 of the supply nozzle 40 located along the second concentric circle which is outside the first concentric circle is positioned higher than the supply port 41 of the supply nozzle 40 located along the first concentric circle. This makes it possible to further reduce surface irregularities near the top of the polycrystalline silicon SL. 【0052】 Furthermore, in Examples 1, 3 to 5, when the surface of the inner wall 111 is made of silver, it is possible to reduce the power consumption per unit of production in the manufacturing apparatus 1 while reducing the surface irregularities that occur near the top of the polycrystalline silicon SL. 【0053】 <Surface irregularities on polycrystalline silicon SL> Figure 4 shows polycrystalline silicon SL with no surface irregularities and polycrystalline silicon SL with surface irregularities. Reference numeral 401 in Figure 4 indicates polycrystalline silicon SL with no surface irregularities, and reference numeral 402 in Figure 4 indicates polycrystalline silicon SL with surface irregularities. 【0054】 Here, if the raw material gas G1 is not stably supplied to the surface of each silicon core wire 20 during the growth process of the polycrystalline silicon SL, irregularities may occur on the surface of the polycrystalline silicon SL, as shown by reference numeral 402 in Figure 4. When irregularities occur, the current path changes, causing an imbalance in the current, and localized high-temperature areas may occur, potentially leading to partial melting of the surface of the polycrystalline silicon SL. 【0055】Furthermore, closed pores may be formed when polycrystalline silicon precipitates on the depressions of these irregularities. Thus, the occurrence of irregularities may cause shape defects in the polycrystalline silicon SL. Moreover, if the polycrystalline silicon SL has irregularities, the amount of fine powder generated during the transport of the polycrystalline silicon SL increases, raising concerns that the yield of single-crystal silicon obtained by single-crystallizing the polycrystalline silicon SL will decrease. For this reason, it is preferable that the raw material gas G1 be supplied in a way that can reduce the occurrence of irregularities. 【0056】 <Method for measuring surface cone ratio> If the maximum temperature of polycrystalline silicon SL inside the manufacturing apparatus 1 is kept below a certain value, it is possible to make the surface cone ratio zero regardless of the shape and arrangement of the supply nozzles 40. However, the deposition rate will decrease, and it will become impossible to achieve the target production volume without investing a large amount of operating time and electricity. In other words, the operation of the manufacturing apparatus 1 will be such that the power consumption per unit is industrially unacceptable. Therefore, in order to compare the superiority or inferiority of the temperature distribution inside the manufacturing apparatus 1 depending on the arrangement of the supply nozzles 40 in this embodiment, the power input to the manufacturing apparatus 1 was adjusted, and data from production lots in which the difference between each embodiment in production volume and power consumption was within 3% was adopted. 【0057】 Figure 5 is a diagram illustrating the measurement method for the surface cone ratio shown in Table 1. The surface cone ratio was measured as follows. As shown by reference numeral 501 in Figure 5, the polycrystalline silicon SL was divided vertically at intervals of 100 mm. The upper part of the polycrystalline silicon SL, including the U-shaped curved section, was divided into three sections as shown by reference numeral 501 in Figure 5. 【0058】 Reference numeral 502 in Figure 5 is an enlarged view showing one piece after division. Next, each piece, which had been 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 there were irregularities or if the surface was smooth by visually inspecting the central region R of the surface, which corresponds to the surface of the polycrystalline silicon SL. 【0059】In this determination, a surface was judged to have unevenness if the shadows cast by the steps formed a mesh pattern under typical indoor lighting of 300 to 500 lux. If a nugget 81 with unevenness is designated as nugget P, the surface cone ratio can be calculated by dividing the number of nugget P by the total number of nuggets. 【0060】 <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 multiple technical means disclosed in the embodiments are also included in the technical scope of the present invention. 【0061】 1 Manufacturing apparatus 10 Reactor 11 Bell jar 12 Bottom plate 20 Silicon core wire 22 Upper end of silicon core wire 30 Core wire holder 31 Upper end of core wire holder 40 Supply nozzle 41 Supply port 111 Inner wall 112 Ceiling section C1, C2, C3 Concentric circles CT Center G1 Raw material gas L1 First distance L2 Second distance SL Polycrystalline silicon SP Space

Claims

1. A polycrystalline silicon manufacturing apparatus comprising: a bell jar having an inner wall made of a material having an emissivity of 0.1 or less before the deposition of polycrystalline silicon, a bottom plate, a reaction furnace whose interior is sealed by these bell jars, a silicon core wire for deposition of polycrystalline silicon, a core wire holding part for holding the silicon core wire inside the reaction furnace, and a plurality of supply nozzles provided on the bottom plate, with a supply port formed therein for supplying raw material gas to the space inside the reaction furnace, wherein, when the direction perpendicular to the bottom plate is defined as the vertical direction, the first distance along the vertical direction between the supply port of at least one of the plurality of supply nozzles and the upper end of the core wire holding part is 100 mm or more and 500 mm or less.

2. The polycrystalline silicon manufacturing apparatus according to claim 1, characterized in that the second distance along the vertical direction between the upper end of the silicon core wire and the upper end of the core wire holding portion is 2000 mm or more and 2400 mm or less.

3. The apparatus for producing polycrystalline silicon according to claim 1, characterized in that the surface of the inner wall of the bell jar is made of silver, and the surface roughness Ra of the inner wall is 0.400 μm or less.

4. The apparatus for manufacturing polycrystalline silicon according to claim 1, characterized in that the first distance is 1 / 4 or less of the second distance along the vertical direction between the upper end of the silicon core wire and the upper end of the core wire holding portion.

5. The polycrystalline silicon manufacturing apparatus according to claim 1, wherein the plurality of supply nozzles are provided along a plurality of concentric circles centered on the center of the bottom plate when viewed from the vertical direction, and any adjacent concentric circles among the plurality of concentric circles are designated as the first concentric circle and the second concentric circle, and the position of the supply port of the supply nozzle provided along the first concentric circle and the position of the supply port of the supply nozzle provided along the second concentric circle are offset from each other in the vertical direction.

6. When viewed from the vertical direction, with the center of the bottom plate on the inside and the periphery of the bottom plate on the outside, and assuming that the second concentric circle is outside the first concentric circle, the supply port of the supply nozzle provided along the second concentric circle is located at a higher position than the supply port of the supply nozzle provided along the first concentric circle, as described in claim 5.

7. The polycrystalline silicon manufacturing apparatus according to claim 1, characterized in that the supply ports of all the supply nozzles provided on the bottom plate are positioned at or above the upper end of the core wire holding portion.

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