Method for producing polysilicon rod

Abstract

The present invention improves the resistivity value of a polysilicon rod precipitated at an early stage of a growth period while preventing collapse of the polysilicon rod at the early stage of the growth period. This method for producing a polysilicon rod (S1) involves supplying a raw material gas (G1) containing a chlorosilane to a silicon core wire erected in the inside of a reaction furnace (10) and obtained by performing electrical-heating, thereby precipitating polysilicon to the surface of the silicon core wire and growing the same into a polysilicon rod (S1) having a diameter of 80 mm or more. The raw material gas (G1) is introduced into the reaction furnace (10) in a manner that the number of gas exchange representing the introduction amount of the raw material gas (G1) into the reaction furnace (10) with respect to the volume of the reaction furnace (10), in a growth start period (T1) of the polysilicon rod (S1) until one hour passes from the start of precipitation of the polysilicon to the surface of the silicon core wire, is not less than 8 times but less than 35 times.

Description

Polysilicon rod manufacturing method

[0001] The present invention relates to a method for manufacturing a polysilicon rod.

[0002] In the production of polysilicon used as a raw material for semiconductor devices, solar cells, etc., a method is known in which raw material gases of chlorosilanes and hydrogen are injected into a reactor to deposit polysilicon rods.

[0003] For example, in Patent Document 1, the flow rate of chlorosilane is increased to 1 m of the silicon surface within 15 hours from the start of deposition. ２ 460 kg of chlorosilane per hour (kg / (h m ２ )) and maintains the flow rate constant for the remaining required charging time. Also, Patent Document 2 discloses a method for manufacturing a polysilicon rod in which the amount of source gas is maintained at a constant flow rate in the initial stage of the deposition reaction, and then the flow rate is gradually increased until the maximum flow rate is 3 to 6 times the initial flow rate.

[0004] Japanese Patent Publication No. 2010-540395 Japanese Patent Publication No. 2014-028747

[0005] In the methods for manufacturing polysilicon rods, including those described in Patent Documents 1 and 2, the polysilicon rod deposited in the early stage of the growth period generally has a low resistivity. In addition, the diameter of the polysilicon rod is small in the early stage of the growth period, and depending on the amount of mixed gas introduced into the reactor, the polysilicon rod may shake and collapse.

[0006] One aspect of the present invention aims to improve the resistivity of polysilicon rods deposited early in the growth period while preventing collapse of the polysilicon rods early in the growth period.

[0007] In order to solve the above-mentioned problems, one aspect of the present invention provides a method for manufacturing a polysilicon rod, which comprises supplying a raw material gas containing chlorosilanes to a silicon core wire that is erected inside a reactor and heated by electrical current, thereby depositing polysilicon on the surface of the silicon core wire and growing it into a polysilicon rod having a diameter of 80 mm or more, and wherein the raw material gas is introduced into the reactor so that the number of gas exchanges, which is the amount of raw material gas introduced into the reactor relative to the volume of the reactor, is 8 or more and less than 35 during the start of growth of the polysilicon rod, from the start of deposition of polysilicon on the surface of the silicon core wire until one hour has elapsed.

[0008] According to one aspect of the present invention, it is possible to improve the resistivity of polysilicon rods deposited in the early stage of the growth period while preventing the polysilicon rods from collapsing in the early stage of the growth period.

[0009] 1 is a schematic diagram showing a polysilicon rod manufacturing apparatus according to a first embodiment of the present invention; FIG. 2 is a graph showing an example of the diameter of a polysilicon rod during deposition versus each deposition time; FIG. 3 is a graph showing the relationship between deposition time and the amount of gas input for examples and comparative examples of the present invention; FIG. 4 is a graph showing the relationship between deposition time and the number of gas exchanges for examples and comparative examples of the present invention; and FIG. 5 is a graph showing the measurement results of the resistivity values ​​of polysilicon rods of examples and comparative examples of the present invention.

[0010] An embodiment of the present invention will be described in detail below. However, the following description is an example of the manufacturing apparatus 1 for manufacturing polysilicon rods S1 and the manufacturing method thereof according to the present invention, and the technical scope of the present invention is not limited to the examples shown in the drawings and the detailed description of the preferred embodiment.

[0011] [Overview of Polysilicon Rod Manufacturing Method] One method for manufacturing polysilicon rods S1 involves supplying a source gas G1 containing chlorosilanes to a silicon core wire (not shown) that is erected in a reactor 10 and heated by electrical current, thereby depositing polysilicon on the surface of the silicon core wire and growing the polysilicon rod S1. In this method for manufacturing polysilicon rods S1, the resistivity of the polysilicon rod S1 deposited during a polysilicon rod growth start period T1 (see FIG. 2 ), which is the period from the start of polysilicon deposition on the silicon core wire surface until one hour has elapsed, may be low. Furthermore, during the growth start period T1, the diameter of the polysilicon rod S1 is small, and depending on the rate of introduction of the source gas G1 into the reactor 10, the polysilicon rod S1 may shake and collapse.

[0012] The method for manufacturing the polysilicon rods S1 according to the present invention prevents the collapse of the polysilicon rods S1 during the growth start period T1 and improves the resistivity of the deposited polysilicon rods S1 by setting the number of gas exchanges in the reactor 10 to the number of gas exchanges discovered by the inventors through extensive research.

[0013] 1 is a schematic diagram showing an apparatus 1 for manufacturing a polysilicon rod S1 according to embodiment 1 of the present invention. As shown in FIG. 1, the apparatus 1 for manufacturing a polysilicon rod S1 includes a control unit 2, a mixer 3, a reactor 10, a supply pipe 20, a supply nozzle 40, an electrode 50, and a discharge pipe 60.

[0014] Here, the diameter of the supply nozzles 40 and the number of supply nozzles 40 installed in the reactor 10 are not particularly limited, but as an example, the diameter of the supply nozzles 40 may be 14φ or more and 18φ or less, and the number of supply nozzles 40 may be 10 to 30.

[0015] The reactor 10 is composed of a bottom 11 on which the polysilicon rod S1 is placed, and a bell-jar-shaped lid 12 that is detachably connected to the bottom 11. The reactor 10 contains a source gas G1 for silicon deposition with the lid 12 connected to the bottom 11. The source gas G1 is a mixed gas, and contains chlorosilanes and hydrogen (H ２ ) are mixed by a mixer 3 and then fed into a reactor 10. The chlorosilanes are, for example, gaseous monochlorosilane (SiH ３ Cl), dichlorosilane (SiH ２ Cl ２ ), trichlorosilane (SiHCl ３ ), tetrachlorosilane (SiCl ４ ) alone or in a mixture.

[0016] The bottom 11 is formed with an inlet 111 through which a raw material gas G1 flows into the reaction furnace 10 and an outlet 112 through which exhaust gas after the reaction in the reaction furnace 10 is discharged. A through-hole H1 extends from the inlet 111 through the bottom 11. A through-hole H2 extends from the outlet 112 through the bottom 11. In FIG. 1 , two inlets 111 and one outlet 112 are formed in the bottom 11, but the numbers of inlets 111 and outlets 112 formed in the bottom 11 are not particularly limited.

[0017] The supply pipe 20 is connected to the end of the through-hole H1 opposite the interior of the reactor 10 and supplies the source gas G1 to the through-hole H1. The supply nozzle 40 is a nozzle that protrudes into the reactor 10 from the inlet 111. The supply nozzle 40 is provided at the bottom 11 to allow the source gas G1 flowing in from the inlet 111 to reach the upper part of the reactor 10 and to uniformly grow the polysilicon rods S1. The height of the tip of the supply nozzle 40 is higher than the top of the electrode 50 to prevent the source gas G1 from directly impinging on the vicinity of the electrode 50. Adjusting the linear gas velocity at the tip of the supply nozzle 40 can prevent the polysilicon rods S1 from breaking easily. The supply nozzle 40 is preferably made of a material that is highly resistant to corrosion by the source gas G1, such as carbon.

[0018] The electrodes 50 are components that electrically connect a power source (not shown) and the silicon core wires. The deposition temperature of polysilicon is approximately 600°C or higher. From the viewpoint of rapidly depositing polysilicon on the silicon core wires, the silicon core wires are electrically heated so that the silicon core wires are maintained at a temperature of approximately 900 to 1000°C. At least one pair of electrodes 50 is provided on the bottom 11. The number of electrodes 50 is determined according to the number of silicon core wires to be installed inside the reactor 10.

[0019] The exhaust pipe 60 is a pipe for exhausting gases formed in the silicon deposition process to the outside of the reactor 10. The exhaust pipe 60 extends between the outside of the reactor 10 and the end of the through hole H2 opposite to the exhaust port 112. The gases exhausted from the silicon deposition process include chlorosilanes, hydrogen (H ２ ), hydrogen chloride (HCl), by-products and contaminants. The gases formed and vented during the silicon deposition process are collected and treated.

[0020] The control unit 2 controls the introduction of the source gas G1 into the reaction furnace 10. The control unit 2 controls the introduction of the source gas G1 into the reaction furnace 10 based on the deposition time, the diameter of the polysilicon rod S1, the linear gas velocity at the tip of the supply nozzle 40, etc. The functions of the control unit 2 may be realized by a CPU (Central Processing Unit) executing a program stored in a storage unit (not shown).

[0021] [Method for Manufacturing Polysilicon Rod] The method for manufacturing polysilicon rod S1 of the present application includes a step of introducing the source gas G1 containing chlorosilanes into the reaction furnace 10, to a silicon core wire that is erected inside the reaction furnace 10 and heated by electrical current, thereby depositing polysilicon on the surface of the silicon core wire and growing it into a polysilicon rod S1 having a diameter of 80 mm or more.

[0022] FIG. 2 is a graph showing an example of the diameter of the polysilicon rod S1 during deposition versus each deposition time. Taking into account industrial utility, the diameter of the polysilicon rod S1 is 80 mm or more, preferably 90 to 180 mm. The growth period is generally 50 hours or more, preferably 60 to 150 hours. As shown in FIG. 2 , the polysilicon rod S1 is deposited, for example, over approximately 100 hours until the diameter reaches approximately 130 mm. In the following description, the time from the start of deposition of the polysilicon rod S1 to the completion of deposition (from 0 hours to 100 hours in FIG. 2 ) will be referred to as the growth period T3 (total growth period).

[0023] In this specification, unless otherwise specified, the "diameter of the polysilicon rod S1" refers to the diameter "in a state in which polysilicon has been deposited on the core wire," and the diameter of the polysilicon rod S1 includes the core wire. This diameter is obtained by measuring the distance between the right and left ends of the polysilicon rod S1 with a distance measuring device (not shown) installed outside the reactor 10 through a viewing window (not shown) for observing the inside of the reactor 10, which is installed on the side of the bell-jar-shaped lid 12.

[0024] (Number of Gas Exchanges) <Growth Start Period T1> As described above, the resistivity of the polysilicon rod S1 deposited during the growth start period T1 (the period from the start of polysilicon deposition on the surface of the silicon core wire until one hour has elapsed) may be low. This is presumably due to the following reasons.

[0025] Typically, (1) when the reactor 10 is not in operation, it is filled with a high-purity gas such as hydrogen or nitrogen and maintained therein, and (2) when the production of the polysilicon rod S1 begins, the air inside the reactor 10 is replaced with the high-purity gas or raw material gas, and a purification process is performed before the deposition of polysilicon is carried out.

[0026] However, even if the above-described purification process is performed, it is difficult to discharge all of the contaminants released from the inner walls of the reactor 10 and accumulated in the reactor 10 while the reactor 10 is out of operation, and some of the contaminants inevitably remain in the reactor 10. Therefore, the contaminants remaining in the reactor 10 are incorporated into the deposited polysilicon during the growth start period T1 of the polysilicon rod S1. As a result, it is estimated that the resistivity of the relevant portion decreases.

[0027] Furthermore, during the growth initiation period T1, the diameter of the polysilicon rod S1 is small, and there is a risk that the polysilicon rod S1 will shake and collapse depending on the rate of introduction of the source gas G1 into the reaction furnace 10. Specifically, during the growth initiation period T1, the diameter of the polysilicon core wire is usually as small as 5 to 15 mm, and after the growth initiation period T1 has elapsed, the diameter of the polysilicon rod S1 will be as small as 6 to 18 mm.

[0028] As a result of extensive research, the present inventors have found that by setting the number of gas exchanges in the reaction furnace 10 to 8 or more and less than 35 times, and preferably 10 or more and less than 30 times, during the growth start period T1, it is possible to prevent the polysilicon rods S1 from collapsing during the growth start period T1 and improve the resistivity of the deposited polysilicon rods S1.

[0029] Conventionally, the number of gas exchanges during the growth start period T1 is typically less than eight, but the present inventors have discovered that by increasing the number of gas exchanges to eight or more, it is possible to properly discharge contaminants generated in the reaction furnace 10. This significantly improves the resistivity of the polysilicon rods S1 deposited during the growth start period T1.

[0030] On the other hand, increasing the number of gas exchanges increases the linear gas velocity at the tip of the supply nozzle 40, which increases the load on the thin-diameter polysilicon rod S1 during the growth start period T1. However, the present inventors have found that limiting the number of gas exchanges to less than 35 prevents the load from increasing to the point where the polysilicon rod S1 collapses.

[0031] Moreover, by increasing the number of gas exchanges and the amount of gas input in this way, the growth rate of the diameter of the polysilicon rod S1 increases, the diameter of the polysilicon rod S1 reaches a thickness large enough to prevent collapse more quickly, and the productivity of the polysilicon rod S1 also improves. Note that, if the number of gas exchanges is 35 or more during the growth start period T1, the collapse rate of the polysilicon rod S1 increases, and productivity deteriorates.

[0032] Here, the number of gas exchanges is the amount of raw material gas G1 input into the reaction furnace 10 relative to the internal volume of the reaction furnace 10 per hour, and is calculated by (amount of raw material gas G1 input into the reaction furnace 10) / (internal volume of the reaction furnace 10), and the unit is times / h.

[0033] During the growth start period T1 of the polysilicon rod S1, the linear velocity of the source gas G1 introduced into the reaction furnace 10 per the supply nozzle 40 is 40 Nm ３ / (s.m. ２ ) or less. This can further enhance the effect of preventing the collapse of the polysilicon rods S1. The linear velocity of the source gas G1 per supply nozzle 40 is 35 Nm ３ / (s.m. ２ ) or less is more preferable.

[0034] The lower limit of the linear velocity is determined appropriately depending on the diameter of the supply nozzle 40. For example, the lower limit of the linear velocity is 5.0 Nm ３ / (s.m. ２ ) or more 20.0Nm ３ / (s.m. ２ By setting the linear velocity of the supply nozzle 40 to a value exceeding the above range, the source gas G1 can be sufficiently distributed throughout the upper part of the reaction furnace 10.

[0035] The "linear velocity" is the linear velocity of gas at the tip of the supply nozzle 40, calculated by "amount of gas introduced / (cross-sectional area of ​​nozzle x number of nozzles)".

[0036] <Initial Growth Period T2> In the method for manufacturing the polysilicon rod S1, the source gas G1 is supplied to the reaction furnace 10 even after the growth start period T1 during the growth period T3 until the polysilicon rod S1 grows to a desired diameter of 80 mm or more. The supply amount of the source gas G1 is generally increased after the growth start period T1 until the deposition of polysilicon is completed. During the growth period T3, the maximum number of gas exchanges per hour is preferably 80 to 100 times.

[0037] If any one hour in the growth period T3 is defined as the arbitrary period TE, and the one hour immediately preceding the arbitrary period TE is defined as the arbitrary period TE-1, the input amount of the source gas G1 after the growth start period T1 may be temporarily maintained at the same input amount as the input amount of the arbitrary period TE-1, or may be reduced from the input amount of the arbitrary period TE-1, depending on the elapsed time from the start of deposition.

[0038] During growth period T3, even after growth initiation period T1 has elapsed, for a certain period following growth initiation period T1, small amounts of contaminants remain in reactor 10, although not as much as during growth initiation period T1. Therefore, there is a risk that contaminants remaining in reactor 10 during the certain period following growth initiation period T1 will be incorporated into the deposited polysilicon, thereby reducing the resistivity.

[0039] In particular, the decrease in resistivity is likely to occur during the initial growth period T2 (see FIG. 2) following the growth start period T1 of the polysilicon rod S1 until its diameter reaches 30 mm.

[0040] Therefore, during the initial growth period T2, it is more preferable to introduce the source gas G1 into the reaction furnace 10 in such a manner that (1) the increase factor of the number of gas exchanges per hour during the initial growth period T2 is within the range of 0.6 to 5.0, and (2) the number of gas exchanges has increased to 30 to 50 times in the hour before the diameter of the polysilicon rod S1 reaches 30 mm. This makes it possible to further reduce the incorporation of contaminants into the polysilicon while continuing to prevent the collapse of the polysilicon rod S1 during the initial growth period T2. Here, the "increase factor of the number of gas exchanges per hour" is calculated by "(the number of gas exchanges in the arbitrary period TE) / (the number of gas exchanges in the arbitrary period TE-1)."

[0041] If gas exchange is performed within the above-mentioned range in the initial growth period T2, the resistivity value can be kept low while preventing collapse of the polysilicon rod S1 even in the initial growth period T2, following the growth start period T1 in which the number of gas exchanges is 8 or more and less than 35 times.

[0042] In the initial growth period T2, gas exchange is performed with the increase factor of the number of gas exchanges in the range of 0.6 to 5.0, more preferably 0.7 to 3.5, and particularly preferably 0.8 to 3.4.

[0043] Furthermore, the number of gas exchanges during the initial growth period T2 can be reduced relative to the number of gas exchanges during the arbitrary period TE-1 as long as the increase factor is 0.6 or more. However, such a reduction period should be limited to a temporary period, and the number of gas exchanges should be increased to 30 to 50 times, more preferably 35 to 45 times, in the hour before the diameter of the polysilicon rod S1 reaches 30 mm.

[0044] Here, the time from the start of deposition of polysilicon on the surface of the silicon core wire to the end of the initial growth period T2, in other words, the time from the start of deposition of polysilicon to the time when the diameter of the polysilicon rod S1 reaches 30 mm, is typically 10 to 30 hours.

[0045] During the initial growth period T2, the linear velocity of the source gas G1 introduced into the reaction furnace 10 per the supply nozzle 40 is 15 Nm ３ / (s.m. ２ ) or more 150Nm ３ / (s.m. ２ ) or less. This can further enhance the effect of preventing the collapse of the polysilicon rods S1. The linear velocity of the source gas G1 per supply nozzle is preferably 20 Nm ３ / (s.m. ２ ) or more 120Nm ３ / (s.m. ２ ) or less is more preferable.

[0046] Example 1 Example 1 of the present invention will be described with reference to Figures 3 to 5. Figure 3 is a graph showing the relationship between deposition time and the amount of gas input for an example of the present invention and a comparative example. More specifically, Figure 3 is a graph showing the amount of gas input to the reactor 10 for each hour that has elapsed since the start of deposition.

[0047] 4 is a graph showing the relationship between deposition time and the number of gas exchanges for the examples and comparative examples of the present invention. More specifically, FIG. 4 is a graph showing the number of gas exchanges per hour after the start of deposition. FIG. 5 is a graph showing the measurement results of the resistivity of polysilicon rod S1 for the examples and comparative examples of the present invention. In FIGS. 3 to 5, a1-1 shows the results for Example 1, and a1-2, b1-1, and b1-2 show the results for Example 2, Comparative Example 1, and Comparative Example 2, respectively, which will be described later.

[0048] In Example 1, polysilicon rods S1 were manufactured using the manufacturing apparatus 1 shown in Fig. 1. The reactor 10 was capable of erecting 10 polycrystalline silicon rods (five pairs of inverted U-shaped polysilicon rods S1), and in Example 1, five pairs of inverted U-shaped silicon core wires each having a height of 2000 mm were erected on the bottom 11 of the reactor 10.

[0049] Each silicon core wire in the reactor 10 was heated by electrical current until its temperature reached approximately 1000°C, and a mixed gas of trichlorosilane and hydrogen was used as the source gas G1, which was introduced from the supply nozzles 40 to carry out a silicon deposition reaction by the Siemens method for 100 hours. Six supply nozzles 40 were provided, and they were evenly spaced over almost the entire upper surface of the bottom 11.

[0050] As a result, the diameter of the polysilicon rod S1 grew to 130 mm, as shown in the graph of Fig. 2. Note that the diameter was the average of the ten polysilicon rods S1 produced, and in this example, the physical properties of the polysilicon rods S1 were also evaluated based on the average of the ten rods.

[0051] In the production of the polysilicon rod S1, during the growth start period T1 from the start of deposition until one hour has elapsed, the source gas G1 is supplied at a flow rate of 243 Nm as shown in a1-1 of FIG. ３ The gas was fed into the reactor 10 at an input rate of 1000000000000 / h.

[0052] The number of gas exchanges during the growth initiation period T1 was 19, as shown in a1-1 of FIG. 4. At the end of the growth initiation period T1, the linear velocity of the source gas G1 introduced into the reaction furnace 10 per the supply nozzle 40 was 30.9 Nm ３ / (s.m. ２ ) was.

[0053] At the end of the growth initiation period T1, none of the growing polysilicon rods S1 collapsed. At the end of the growth initiation period T1, the diameter of the polysilicon rods S1 reached 11 mm.

[0054] Following the growth initiation period T1, during an initial growth period T2 until the diameter of the polysilicon rod S1 reached 30 mm, the source gas G1 was introduced into the reaction furnace 10 at the gas introduction amount shown in a1-1 of Fig. 3 and with the number of gas exchanges shown in Fig. 4. The time elapsed from the start of deposition until the diameter of the polysilicon rod S1 reached 30 mm was 21 hours.

[0055] During the initial growth period T2, the rate of increase in the number of gas exchanges per hour was in the range of 0.9 to 2.0. Furthermore, the number of gas exchanges increased to 45 times in the hour before the diameter of the polysilicon rod S1 reached 30 mm. During this initial growth period T2, the linear velocity of the source gas G1 introduced into the reaction furnace 10 per supply nozzle 40 was 30.9 to 72.7 Nm. ３ / (s.m. ２ Even during this initial growth period T2, not a single polysilicon rod S1 collapsed.

[0056] Furthermore, following the initial growth period T2, during the period from the start of deposition until 100 hours had elapsed, the number of gas exchanges was gradually increased to a maximum value of 95 times 42 hours after the start of deposition, and thereafter, the increase factor of the number of gas exchanges per hour was set to a range of 0.0 to 1.5, and the source gas G1 was introduced into the reaction furnace 10. Furthermore, during the final hour at the end of growth, the number of gas exchanges was set to 0. As described above, growth was terminated when 100 hours had elapsed from the start of deposition, and a polysilicon rod S1 having a diameter of approximately 130 mm was obtained.

[0057] After the polysilicon rod S1 was manufactured as described above, a core rod having a diameter of 19 mm was bored from the obtained polysilicon rod S1 in a direction perpendicular to the longitudinal direction of the rod S1 and including the core portion, and the resistivity of the core rod in the longitudinal direction was measured to determine the resistivity of the polysilicon rod S1 in the radial direction. The results are shown as a1-1 in Figure 5. On the horizontal axis of Figure 5, for example, "core + 2 cm" indicates a state in which polysilicon is deposited around the core to a thickness of about 1 cm (i.e., a diameter 2 cm larger than the diameter of the core).

[0058] 5, the resistivity value Xa1-1 of the polysilicon rod S1 having a diameter X at the end of the growth start period T1, one hour after the start of polysilicon deposition, was a high value of approximately 1700 (Ωcm). Also, the resistivity value Ya1-1 of the polysilicon rod S1 at the end of the initial growth period T2, when the diameter of the polysilicon rod S1 reached 30 mm (diameter Y), was approximately 3600 (Ωcm), and the high resistivity value was well maintained.

[0059] 3 to 5, Comparative Example 1 of the present invention will be described. In Comparative Example 1, polysilicon rods S1 were manufactured in the same manner as in Example 1, except that the amount of source gas G1 introduced during the growth start period T1 and the initial growth period T2 was changed as follows. Comparative Example 1 is a method for manufacturing polysilicon rods S1 using the amount of gas introduced that is generally used in the past.

[0060] In Comparative Example 1, the input amount of source gas G1 during the growth start period T1 was 88 Nm ３ / h, and the number of gas exchanges during the growth initiation period T1 was reduced to 7 times as shown in b1-1 of FIG. 4. At the end of the growth initiation period T1, the linear velocity of the source gas G1 introduced into the reaction furnace 10 per supply nozzle 40 was 9.7 Nm ３ / (s.m. ２ ) was.

[0061] During the initial growth period T2, the source gas G1 was introduced into the reaction furnace 10 at the gas introduction amount shown in b1-1 of Fig. 3 and with the gas exchange frequency shown in Fig. 4. The time elapsed from the start of deposition until the diameter of the polysilicon rod S1 reached 30 mm was 21 hours.

[0062] During the initial growth period T2, the rate of increase in the number of gas exchanges per hour was in the range of 0.9 to 1.6. In addition, the number of gas exchanges increased to 27 times in the hour before the diameter of the polysilicon rod S1 reached 30 mm. During the initial growth period T2, the linear velocity of the source gas G1 introduced into the reaction furnace 10 per supply nozzle 40 was 9.7 to 37.8 Nm ３ / (s.m. ２ ) range.

[0063] In the production of the polysilicon rod S1 of Comparative Example 1, none of the polysilicon rods S1 collapsed after the growth start period T1 had elapsed. After the growth start period T1 had elapsed, the diameter of the polysilicon rod S1 had reached approximately 11 mm.

[0064] Subsequently, during the initial growth period T2, none of the polysilicon rods S1 collapsed. During the initial growth period T2, the diameter of the polysilicon rods S1 reached approximately 30 mm.

[0065] A core rod was hollowed out from the obtained polysilicon rod S1, as in Example 1, and the resistivity in the longitudinal direction was determined, which is shown as b1-1 in Figure 5. The resistivity Xb1-1 of the polysilicon rod S1 having a diameter X at the end of the growth start period T1 was approximately 480 (Ωcm), which was a value approximately 28% lower than that of Example 1. Furthermore, the resistivity Yb1-1 of the polysilicon rod S1 at the end of the initial growth period T2, when the diameter of the polysilicon rod S1 reached 30 mm (diameter Y), was approximately 980 (Ωcm), which was a value approximately 27% lower than that of Example 1.

[0066] 3 to 5, Comparative Example 2 of the present invention will be described. In Comparative Example 2, polysilicon rods S1 were manufactured in the same manner as in Example 1, except that the amount of source gas G1 introduced during the growth start period T1 was changed as follows:

[0067] In Comparative Example 2, the input amount of source gas G1 during the growth start period T1 was 518 Nm as shown in b1-2 of FIG. ３ / h, and the number of gas exchanges during the growth initiation period T1 was increased to 40 times as shown in b1-2 of FIG. 4. During the growth initiation period T1, the linear velocity of the source gas G1 introduced into the reaction furnace 10 per supply nozzle 40 was 65.7 Nm ３ / (s.m. ２ ) was.

[0068] In Comparative Example 2, after the growth start period T1 had elapsed, one pair (two rods) of the ten polysilicon rods S1 collapsed, and the collapsed polysilicon rods S1 leaned on the other polysilicon rods S1, resulting in the collapse of all the polysilicon rods S1.

[0069] 3 to 5, a description will be given of Example 2 of the present invention. In Example 2, a polysilicon rod S1 was manufactured in the same manner as in Example 1, except that the amount of source gas G1 introduced during the growth start period T1 and the initial growth period T2 was changed as follows:

[0070] In Example 2, the amount of gas input during the growth start period T1 was 162 Nm as shown in a1-2 of FIG. ３ / h, and the number of gas exchanges during the growth initiation period T1 was reduced to 13 times as shown in a1-2 of FIG. 4. At the end of the growth initiation period T1, the linear velocity of the source gas G1 introduced into the reaction furnace 10 per supply nozzle 40 was 20.6 Nm ３ / (s.m. ２ ) was.

[0071] During the initial growth period T2, the source gas G1 was introduced into the reaction furnace 10 at the gas introduction amount shown in a1-2 of Fig. 3 and with the gas exchange frequency shown in Fig. 4. The time elapsed from the start of deposition until the diameter of the polysilicon rod S1 reached 30 mm was 21 hours.

[0072] During the initial growth period T2, the rate of increase in the number of gas exchanges per hour was in the range of 0.8 to 2.2. In addition, the number of gas exchanges increased to 30 times in the hour before the diameter of the polysilicon rod S1 reached 30 mm. During this initial growth period T2, the linear velocity of the source gas G1 introduced into the reaction furnace 10 per supply nozzle 40 was 20.6 to 48.7 Nm ３ / (s.m. ２ ) range.

[0073] In the production of the polysilicon rod S1 in Example 2, none of the polysilicon rods S1 collapsed after the growth start period T1 had elapsed. After the growth start period T1 had elapsed, the diameter of the polysilicon rod S1 had reached approximately 11 mm.

[0074] Subsequently, during the initial growth period T2, none of the polysilicon rods S1 collapsed. During the initial growth period T2, the diameter of the polysilicon rods S1 reached approximately 30 mm.

[0075] A core rod was hollowed out from the obtained polysilicon rod S1 in the same manner as in Example 1, and the resistivity in the longitudinal direction was determined, which is shown as a1-2 in Figure 5. The resistivity Xa1-2 of the polysilicon rod S1 having a diameter X at the end of the growth start period T1 was a high value of approximately 940 (Ωcm). Furthermore, the resistivity Ya1-2 of the polysilicon rod S1 at the end of the initial growth period T2, when the diameter of the polysilicon rod S1 reached 30 mm (diameter Y), was approximately 2050 (Ωcm), and the high resistivity value was well maintained.

[0076] [Summary] A method for manufacturing a polysilicon rod according to a first aspect of the present invention is a method for manufacturing a polysilicon rod (S1) by supplying a source gas (G1) containing chlorosilanes to a silicon core wire that is erected inside a reactor (10) and heated by electrical current, thereby depositing polysilicon on the surface of the silicon core wire and growing the polysilicon rod (S1) having a diameter of 80 mm or more, wherein the source gas (G1) is introduced into the reactor (10) so that the number of gas exchanges, which is the amount of the source gas (G1) introduced into the reactor (10) relative to the volume of the reactor (10), is 8 or more and less than 35 times during a polysilicon rod growth start period (T1) from the start of polysilicon deposition on the surface of the silicon core wire until one hour has elapsed.

[0077] As a result of extensive research, the present inventors have found that by setting the number of gas exchanges in the reactor (10) to 8 or more and less than 35 times per unit time, it is possible to prevent the polysilicon rods (S1) from collapsing during the growth start period (T1) and improve the resistivity of the deposited polysilicon rods (S1).

[0078] Therefore, according to the above configuration, it is possible to prevent the polysilicon rods (S1) from collapsing during the growth start period (T1), while improving the resistivity of the polysilicon rods (S1) deposited during the growth start period (T1).

[0079] A method for producing a polysilicon rod according to a second aspect of the present invention may be carried out in the above-described first aspect, wherein during an initial growth period (T2) of the polysilicon rod (S1) following the lapse of the growth start period (T1) of the polysilicon rod and until the polysilicon rod (S1) reaches a diameter of 30 mm, the supply of the source gas (G1) into the reaction furnace (10) is carried out in such a manner that (1) an increase factor of the number of gas exchanges per hour during the initial growth period (T2) of the polysilicon rod is in the range of 0.6 to 5.0, and (2) the number of gas exchanges increases to 30 to 50 times in the hour before the diameter of the polysilicon rod (S1) reaches 30 mm.

[0080] At the start of deposition, the diameter of the polysilicon rod (S1) is small, so increasing the amount of gas input may cause the polysilicon rod (S1) to collapse. According to the above configuration, the amount of gas input can be increased as the polysilicon rod (S1) grows and thickens due to deposition, increasing its strength. This makes it possible to achieve both the collapse of the polysilicon rod (S1) and appropriate deposition of the polysilicon rod (S1).

[0081] A method for producing a polysilicon rod according to a third aspect of the present invention is the method for producing a polysilicon rod according to the first or second aspect, wherein, during the growth start period (T1), the source gas (G1) is introduced into the reaction furnace (10) by a supply nozzle (40), and the linear velocity of the source gas (G1) introduced into the reaction furnace (10) per supply nozzle (40) is 40 Nm ３ / (s.m. ２ ) or less.

[0082] During the growth start period (T1) of the polysilicon rod (S1), if the linear velocity of the source gas (G1) per supply nozzle (40) introduced into the reactor (10) is too high, this may cause the polysilicon rod (S1) to collapse. According to the above configuration, the source gas (G1) is introduced at a linear velocity per supply nozzle (40) that allows the polysilicon rod (S1) to maintain its independence, thereby further reducing the possibility of the polysilicon rod (S1) collapsing during the growth start period (T1).

[0083] In the method for producing a polysilicon rod according to Aspect 4 of the present invention, in any one of Aspects 1 to 3, the maximum number of gas exchanges per hour during the entire growth period (growth period T3) of the polysilicon rod (S1) may be 80 to 100 times.

[0084] According to the above configuration, the source gas (G1) can be introduced into the reaction furnace (10) so that the polysilicon rod (S1) does not collapse during the entire growth period of the polysilicon rod (growth period T3).

[0085] The present invention is not limited to the above-described embodiments, 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. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0086] 1 Manufacturing equipment 10 Reactor 40 Supply nozzle G1 Source gas S1 Polysilicon rod T1 Growth start period T2 Initial growth period T3 Growth period (total growth period)

Claims

1. A method for manufacturing a polysilicon rod, comprising: supplying a raw material gas containing chlorosilanes to a silicon core wire that is set upright inside a reactor and heated by electrical current, thereby precipitating polysilicon on the surface of the silicon core wire and growing it into a polysilicon rod having a diameter of 80 mm or more; wherein the raw material gas is fed into the reactor so that the number of gas exchanges, which is the amount of raw material gas fed into the reactor relative to the volume of the reactor, during the start of the growth of the polysilicon rod from the start of polysilicon precipitation on the surface of the silicon core wire to the elapse of one hour, is 8 or more and less than 35 times.

2. The method for producing a polysilicon rod according to claim 1, wherein, during an initial growth period of the polysilicon rod following the lapse of the growth start period of the polysilicon rod until the diameter of the polysilicon rod reaches 30 mm, the supply of the source gas into the reaction furnace is carried out in such a manner that (1) the increase rate of the number of gas exchanges per hour during the initial growth period is within a range of 0.6 to 5.0, and (2) during the hour before the diameter of the polysilicon rod reaches 30 mm, the number of gas exchanges increases to 30 times or more and 50 times or less.

3. During the growth start period, the source gas is fed into the reactor through a feed nozzle, and the linear velocity of the source gas fed into the reactor per the feed nozzle is 40 Nm ３ / (s.m. ２ 3. The method for producing a polysilicon rod according to claim 1, wherein the average particle diameter is 100 nm or less.

4. The method for producing a polysilicon rod according to claim 1 or 2, wherein the maximum number of gas exchanges per hour is 80 to 100 times during the entire growth period of the polysilicon rod.

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