JP2016138021A - Method and apparatus of manufacturing polycrystalline silicon rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus of manufacturing a polycrystalline silicon rod capable of reducing a unit consumption of electric power, and improving productivity.SOLUTION: The method of manufacturing a rod 20 composed of polycrystalline silicon comprises using a reactor 2 provided with at least a pair of electrodes 12 for electrifying a silicon core wire and having a cooling passage for flowing a coolant to cool an inner wall, connecting the silicon core wire 12 to the electrodes, and supplying a raw material gas for precipitating silicon into the reactor 2 while electrifying the silicon core wire to precipitate polycrystalline silicon on the silicon core wire 12. The flow rate of the coolant flowing through the cooling passage up to a heat-evolving rate of at least 50% of a maximum heat evolving rate in the precipitating reaction of silicon is controlled so as to be smaller than a flow rate at the maximum heat evolving rate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method and apparatus for manufacturing a polycrystalline silicon rod.

Various methods for producing silicon used as a raw material for semiconductors or wafers for photovoltaic power generation are known, some of which have already been industrially implemented. One of the methods is a method called a Siemens method, which is connected to the electrode inside a so-called bell jar type reactor comprising a bottom plate and a cover provided with at least a pair of electrodes for energizing the silicon core wire. The arranged silicon core wire is heated to a silicon deposition temperature by energization, and a gas of a silane compound such as trichlorosilane (SiHCl ₃ ) or monosilane (SiH ₄ ) and hydrogen are supplied thereto, and silicon is deposited by chemical vapor deposition. In this method, silicon is deposited on the core wire.

  Here, the deposition temperature of silicon is about 600 ° C. or higher, and the silicon core wire is heated by energization so as to be generally maintained at a temperature of about 900 to 1200 ° C. On the other hand, in order to remove heat generated by energization, the reactor has a double structure in which at least a part of the wall constituted by the bottom plate and the cover forms a cooling channel for circulating the refrigerant. The cooling of the inner wall was performed by flowing a low-temperature refrigerant through the cooling passage (Patent Document 1).

  Conventionally, the cooling with the above refrigerant predicts the maximum heat generation amount in the reaction in order to prevent deterioration of the reactor due to temperature increase in the precipitation reaction and deterioration of the quality of the silicon rod obtained by silicon deposition on the silicon core wire. The reactor was cooled while maintaining the constant flow rate at the determined flow rate (hereinafter also referred to as the maximum flow rate).

  However, in the reactor, in order to increase the production amount per unit of the reactor for the purpose of improving the productivity, when trying to increase the deposition amount of silicon per unit time by introducing a large current, It turns out that a problem arises.

  That is, as described above, the supply of the refrigerant to the reactor is determined by predicting the maximum heat generation amount in the silicon deposition reaction, and when the silicon deposition amount is greatly increased, The maximum calorific value increases, thereby increasing the maximum flow rate of the refrigerant determined as a result. As a result, during the preheating of the silicon core wire, which has not been a problem in the past, the reaction in the reactor is also performed. Until the maximum heating value is reached, the inside of the reactor is excessively cooled, and excessive power is required to maintain the surface temperature of the precipitation part at the set temperature, resulting in a problem that the power consumption rate becomes extremely high. It was found to occur. In particular, the problem is significant when the average production of polycrystalline silicon rods per reactor is 20 kg / hour or more.

  Further, in the conventional research, it has become common knowledge that the maximum flow rate is adopted as the flow rate of the refrigerant supplied to the reactor. In particular, when a sufficiently low-temperature refrigerant is used, the reactivity varies somewhat. However, since it is difficult for the necessary cooling to be performed due to insufficient refrigerant temperature and the above problems cannot be suppressed, it has not been studied at all to change the flow rate of such a refrigerant according to the operating conditions of the reactor. The current situation.

JP 2011-37699 A

  The object of the present invention is to increase the amount of silicon deposited per unit time by applying a large current and improve the productivity per reactor. It is an object of the present invention to provide a method and an apparatus for manufacturing a polycrystalline silicon rod that can be reduced to a low level.

  As a result of repeated studies to solve the above problems, the present inventors have changed the flow rate of the refrigerant according to the operating conditions of the reactor, which was unthinkable in the conventional method, Excessive cooling in the reactor is prevented by adjusting the flow rate of the refrigerant in a specific range up to the maximum heat generation amount in the silicon precipitation reaction to be smaller than the maximum flow rate of the refrigerant in energization. It has been found that the power consumption in production can be effectively reduced and the object can be achieved, and the present invention has been completed.

That is, the present invention uses a reactor having at least one pair of electrodes for energizing the silicon core wire and having a cooling passage for cooling the inner wall by circulating a refrigerant having a temperature equal to or lower than the boiling point under atmospheric pressure conditions. And, while supplying a silicon core wire to the electrode and energizing it, supplying a silicon deposition source gas into the reactor, and producing a polycrystalline silicon rod for depositing polycrystalline silicon on the silicon core wire,
The production amount of polycrystalline silicon rods per reactor is an average of 20 kg / hour or more, and circulates through the cooling passage up to a calorific value of at least 50% of the maximum calorific value in the silicon precipitation reaction. The refrigerant flow rate is adjusted to be smaller than the refrigerant flow rate (maximum flow rate) at the maximum calorific value.

  The polycrystalline silicon rod manufacturing apparatus according to the present invention has conventionally performed the flow rate of the refrigerant in the operation of the reactor consistently at the maximum flow rate, thereby reducing the flow rate of the refrigerant that did not have the function. It is characterized by having means for changing according to the operating conditions of the reactor.

  That is, according to the present invention, there is provided a bottom plate provided with at least one pair of electrodes for energizing the silicon core wire, and a cover that covers the bottom plate, and at least a part of the wall constituted by the bottom plate and the cover is provided. And a reactor having a double structure that forms a cooling passage for circulating the refrigerant to cool the inner wall, and a flow rate adjusting means for adjusting a flow rate of the refrigerant flowing through the cooling passage. A silicon rod manufacturing apparatus is provided.

  According to the method and apparatus for manufacturing a polycrystalline silicon rod according to the present invention, the flow rate of the refrigerant up to at least 50% of the maximum heat generation amount in the silicon precipitation reaction is adjusted to be smaller than the maximum flow rate. Thus, it is possible to prevent excessive cooling in the reactor, reduce the power consumption in silicon deposition, and improve productivity.

  The refrigerant adjustment range is up to at least 50% of the maximum calorific value, preferably up to at least 60%, more preferably up to at least 70%, most preferably over the entire precipitation region. preferable.

In the present invention, the maximum heat generation amount in the silicon precipitation reaction, which determines the maximum flow rate of the refrigerant, is predicted as the amount of heat released from the silicon surface when silicon reaches the final diameter at the end of the precipitation reaction. Usually, it is calculated from the following equation depending on the surface temperature, final diameter, length, number of the polycrystalline silicon rods, and the like.
Amount of heat (Q) = (ε × σ × A × T ⁴ )
A = π × R × H × N
Where ε is the emissivity of silicon, σ is the Stefan-Boltzmann constant, T is the surface temperature of the silicon (K), A is the surface area (m ² ) of the polycrystalline silicon rod, and R is the polycrystalline silicon rod , H is the length of the polycrystalline silicon rod, and N is the number of polycrystalline silicon rods.

  Further, when the maximum flow rate reaches the maximum heat generation amount in the precipitation reaction, the minimum flow rate that can prevent the deterioration of the reactor due to the temperature rise or the deterioration of the quality of the silicon rod obtained by depositing silicon on the silicon core wire. In general, the flow rate is set to 1.05 to 1.5 times, particularly 1.1 to 1.3 times the flow rate.

  For example, stainless steel (SUS), which has excellent corrosion resistance, is generally used as the material for the polycrystalline silicon rod reactor, but the inner wall temperature of the reactor is 500 ° C. even if this is used. If it exceeds the above range, the phenomenon that the mechanical strength is lowered occurs, and it is inappropriate to use the reactor repeatedly. Therefore, if the maximum flow rate is set for the purpose of preventing the deterioration of the reactor due to such a temperature rise, the minimum flow rate may be determined so that the inner wall temperature of the reactor does not exceed 500 ° C. Alternatively, in the precipitation reaction of polycrystalline silicon rods, when the inner wall temperature of the reactor generally exceeds 300 ° C., the inner wall is gradually eroded by corrosive gas such as hydrogen chloride generated in the reactor furnace and contained as impurities. Phosphorus, boron, arsenic, etc. are released. These impurities are not preferable because they act as dopants on silicon and degrade the quality thereof. Therefore, if the maximum flow rate is set for the purpose of preventing such quality deterioration of the silicon rod, the minimum flow rate may be determined so that the inner wall temperature of the reactor does not exceed 300 ° C. Here, the fact that the inner wall temperature of the reactor does not exceed the above set temperatures is sufficient if the substantially entire surface of the inner wall (the upper surface of the bottom plate and the inner surface of the cover) constituting the reactor is satisfied, and the local temperature distribution Even if the set temperature is exceeded at some points (preferably 3% or less of the entire inner wall surface) that do not greatly affect the effect due to mechanical disturbance, it is permissible as not exceeding.

  Conventionally, the reactor was cooled by maintaining the maximum flow rate consistently from the time of turning on the power for preheating the silicon core wire to the end of deposition.

  The flow rate adjustment of the refrigerant may be adjusted to be smaller than the flow rate of the refrigerant at the maximum calorific value, but is preferably higher than the calorific value of each time zone in the precipitation reaction, It is good to adjust so that the difference with the heat removal amount in a belt | band | zone becomes small.

Specifically, the temperature of the refrigerant at the inlet of the cooling passage to the reactor is T1, the temperature of the refrigerant at the outlet of the cooling passage from the reactor is T2,
When the specific heat of the refrigerant is C,
The flow rate of the refrigerant flowing through the cooling passage up to a calorific value of at least 50% of the maximum calorific value in the silicon precipitation reaction, the T1 and T2 being a relational expression of (T2−T1) × C ≧ 9 cal / g It is preferable to adjust so as to satisfy.

  According to the method of the present invention, the flow rate of the refrigerant up to at least 50% of the maximum heat generation amount in the silicon precipitation reaction is adjusted to be smaller than the flow rate of the refrigerant at the maximum heat generation amount, for example, generation By reducing the flow rate of the refrigerant at the initial stage of deposition where the amount of heat is low or during the growth reaction of silicon, excessive power is not required to keep the surface temperature of the deposition part at the set temperature, and the power consumption is kept low. Can do.

FIG. 1 is a schematic view of a polycrystalline silicon rod manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is a schematic view showing temporal changes in the heat removal capability by the refrigerant and the amount of heat generated by energization in the conventional method for producing a polycrystalline silicon rod. FIG. 3 is a schematic diagram showing temporal changes in the heat removal capability by the refrigerant and the amount of heat generated by energization in the method for producing a polycrystalline silicon rod according to the present embodiment. FIG. 4 is a schematic view showing a comparison of changes over time in the growth rate in the radial direction of the polycrystalline silicon rod between the polycrystalline silicon rod manufacturing method of the present embodiment and the conventional polycrystalline silicon rod manufacturing method. FIG. 5 is a schematic view of an apparatus for manufacturing a polycrystalline silicon rod according to another embodiment of the present invention.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
As shown in FIG. 1, the polycrystalline silicon rod manufacturing apparatus according to one embodiment of the present invention has a reactor 2. The polycrystalline silicon rod manufacturing apparatus of this embodiment is for industrial production. The production amount per one reactor 2 is 20 kg / hour or more on average, preferably 20 to 50 kg / hour, more preferably 50 to 80 kg / hour.

  In the present embodiment, the reactor 2 has a bell jar type cover 4 that is detachably connected to the bottom plate 6. In the present embodiment, at least a pair of electrodes 12 are attached to the bottom plate 6. The number of electrodes 12 is determined in accordance with the number of silicon core wires 10 installed in the reactor 2.

  The silicon core wire 10 installed inside the reactor 2 is installed in an inverted U shape so as to connect a pair of electrodes 12 to each other, and can be energized through the electrodes 12. The electrode is made of carbon, SUS, Cu or the like.

  The core wire 10 is made of, for example, polycrystalline silicon, single crystal silicon, or molten solidified silicon. The inverted U-shaped core wire 10 may be formed by connecting a plurality of core wires 10. Polycrystalline silicon is deposited around the core wire 10 to form a rod 20 made of polycrystalline silicon. The rods 20 are formed in a number corresponding to the number of the core wires 10.

  The cover 4 may have a structure in which the ceiling part and the side part are integrated, or may have a structure in which the cover 4 is joined by a flange or welding.

  The cover 4 is preferably provided with at least one transparent and heat-resistant window member 8 through which the inside of the reactor 2 can be observed. A non-contact thermometer 38 such as an infrared temperature sensor may be installed outside the window member 8. The thermometer 38 can measure the surface temperature of the rod 20 disposed inside the reactor 2, and the measured temperature signal is input to the control device 32 disposed outside the reactor 2. The

  In the middle of the supply line for supplying the source gas to the source gas supply port 14, a source gas flow rate controller for adjusting the flow rate of the gas supplied from the source gas supply port 14 into the reactor 2 is mounted. is there. A plurality of source gas supply ports 14 and source gas discharge ports 16 may be provided in a single reactor 2.

  The cover 4 and the bottom plate 6 are made of, for example, stainless metal, carbon steel, nickel-based alloy, iron and a composite material thereof with other metals, heat resistant members such as a heat resistant member such as quartz, particularly stainless steel (SUS). Preferably, it has a double structure consisting of an inner surface and an outer surface. A cooling passage is formed inside each of the double structure of the cover 4 and the bottom plate 6. The cover 4 and the bottom plate 6 supply the refrigerant from the refrigerant supply port 15 and discharge the refrigerant from the refrigerant discharge port 17. The cooling passages 9 are connected.

  The refrigerant is not particularly limited, and includes a liquid heat medium generally used for cooling, such as water, heat medium oil such as Barrel Therm (trade name: manufactured by Muramatsu Oil Co., Ltd.), and of these, water is particularly preferable. .

  The inlet refrigerant temperature T1 in the refrigerant supply port 15 needs to be equal to or lower than the boiling point under atmospheric pressure due to the high cooling efficiency, and even if the refrigerant flow rate is adjusted to be less than the maximum flow rate, Since it is easy to control and deterioration of the reactor can be suppressed, the temperature is required to be 100 ° C. or lower, and preferably 30 to 90 ° C.

  In the middle of the supply line for supplying the refrigerant to the refrigerant supply port 15, a refrigerant flow rate control unit 42 for adjusting the flow rate of the refrigerant supplied from the refrigerant supply port 15 to the inside of the reactor 2 is mounted. The refrigerant flow rate control unit 42 is controlled by the control device 32, and includes, for example, an electromagnetic valve, an air operation valve, a hydraulic operation valve, and an electric valve.

  A temperature detector 50 for detecting the temperature of the refrigerant supplied from the refrigerant supply port 15 to the inside of the reactor 2 is mounted in the middle of the supply line for supplying the refrigerant to the refrigerant supply port. Moreover, the temperature detection part 52 is also attached to the discharge line through which the refrigerant discharged from the refrigerant discharge port 17 passes, and the temperature of the refrigerant discharged from the reactor 2 to the refrigerant discharge port 17 can be detected.

  The detected temperature signal is input to the control device 32 arranged outside the reactor 2.

  It is preferable that the refrigerant discharged from the refrigerant discharge port 17 is re-cooled by a heat exchanger (not shown), adjusted in temperature, and returned to the refrigerant supply port 15, but is heated without being returned. The refrigerant may be used for other purposes.

  A power supply means 30 is connected to the electrode 12 connected to the core wire 10. The power supply means is not particularly limited, and is constituted by, for example, a transformer, a battery, a thyristor, an IGBT or the like. The power supply means 30 is controlled by the control device 32.

  Production of the rod 20 made of polycrystalline silicon using the above-described apparatus is performed as follows. That is, energization to the core wire 10 is started via the electrode 12, and the temperature of the core wire 10 is heated to the silicon deposition temperature or higher by energization heating. The deposition temperature of silicon is about 600 ° C. or higher. However, in order to quickly deposit silicon on the core wire 10, the silicon core wire 10 is generally energized so as to be maintained at a temperature of about 900 to 1200 ° C. Heated.

  At the same time as the energization of the core wire 10 is started, or when the temperature of the core wire 10 reaches the silicon deposition temperature or higher, silane gas and reducing gas are supplied from the source gas supply port 14 into the reactor 2 as source gases. Then, silicon is generated by the reaction of these source gases (reduction reaction of silane).

  As the silane gas supplied from the raw material gas supply port 14, a gas of a silane compound such as monosilane, trichlorosilane, silicon tetrachloride, monochlorosilane, dichlorosilane or the like is used, and generally, trichlorosilane gas is preferably used. . Further, hydrogen gas is usually used as the reducing gas. Taking the case of using trichlorosilane gas and hydrogen gas as an example, this reduction reaction is represented by the following formula.

SiHCl ₃ + H ₂ → Si + 3HCl

  In addition, in said raw material gas, generally reducing gas (hydrogen gas) is used excessively.

  In addition to the above reduction reaction, silicon is also generated by thermal decomposition of trichlorosilane as described below.

4SiHCl ₃ → Si + 3SiCl ₄ + 2H ₂

Moreover, it is also possible to produce silicon by thermal decomposition of monosilane represented by the following formula by supplying only monosilane (SiH ₄ ) as a source gas without using a reducing gas.

SiH ₄ → Si + 2H ₂

  Silicon (Si) generated by the above reaction is deposited on the core wire 10, and by continuing this reaction, silicon on the core wire 10 grows and finally the rod 20 made of polycrystalline silicon. Will be obtained.

  As described above, when the rod 20 having a constant thickness is obtained, the reaction is terminated, the energization to the core wire 10 is stopped, and unreacted silane gas, hydrogen gas and by-product tetrachloride are generated from the reactor 2. After exhausting silicon, hydrogen chloride, etc., the bell jar type cover 4 is opened and the rod 20 is taken out.

  In the present embodiment, the flow rate of the refrigerant up to at least 50% of the maximum calorific value in the silicon precipitation reaction is adjusted to be smaller than the refrigerant flow rate at the maximum calorific value.

  The refrigerant adjustment range is up to at least 50% of the maximum heating value, preferably up to at least 60%, more preferably up to at least 70%, most preferably over the entire precipitation region. preferable.

  Preferably, the flow rate of the refrigerant up to at least 50% of the maximum calorific value in the silicon precipitation reaction is set such that the inlet refrigerant temperature T1 in the refrigerant supply port 15, the outlet refrigerant temperature T2 in the refrigerant discharge port 17, and the solvent The specific heat C is adjusted so as to satisfy the relationship of (T2−T1) × C ≧ 9 cal / g.

  As shown in FIG. 2, the amount of heat generated by energization rises with time, grows to a desired rod, and reaches the maximum heating value immediately before stopping the supply of the raw material gas for silicon deposition (at the end of deposition). Conventionally, the flow rate of the refrigerant has not been adjusted during the preheating of the silicon core wire and further until the reaction in the reactor reaches the maximum calorific value. For this reason, as shown in FIG. 2, an operation was performed in which the flow rate of the refrigerant was made constant in accordance with the maximum heat removal capability required in the silicon precipitation reaction. However, in such an operation, as a result of supplying an excessive amount of refrigerant in the initial stage of precipitation, heat loss in the reactor becomes excessive. As described above, the silicon core wire is energized and heated so as to be maintained at 900 to 1200 ° C., which is the silicon deposition temperature. However, if the heat loss is large, more power is required to maintain the target temperature.

  In contrast, in the present embodiment, the refrigerant flow rate up to at least 50% of the maximum calorific value in the silicon precipitation reaction is adjusted to be smaller than the refrigerant flow rate at the maximum calorific value. As a result, as shown in FIG. 3, in the initial stage of precipitation when the amount of generated heat is small, the heat removal capacity can be kept low by reducing the flow rate of the refrigerant, and the refrigerant increases as the amount of generated heat increases with time. The heat removal capability can be increased by increasing the flow rate of. As a result, safe operation is possible while reducing heat loss. Moreover, since there is little heat loss at the initial stage of deposition, excessive power for maintaining the target temperature is not required, and the power consumption can be suppressed.

  In order to fully exhibit the above effects, the flow rate of the refrigerant up to the maximum calorific value in the silicon precipitation reaction is determined in order to prevent the deterioration of the reactor and the deterioration of the quality of the silicon rod. It is desirable that the required condition of the inner wall temperature of the reactor is satisfied. In the manufacture of a rod made of polycrystalline silicon, when the flow rate of the refrigerant at the maximum calorific value in the silicon precipitation reaction is 1, the silicon precipitation raw material gas is supplied to the reactor to start the precipitation reaction. The flow rate is preferably 0.5 or less, but for the above reason, the initial flow rate of the refrigerant is more preferably 0.2 to 0.4. Furthermore, it is preferable that the average flow rate of the refrigerant up to 50% of the maximum calorific value is 0.4 to 0.7 when the flow rate of the refrigerant at the maximum calorific value in the recon precipitation reaction is 1. Furthermore, the average flow rate of the refrigerant up to 70% of the maximum calorific value is preferably in the above range, and the average flow rate of the refrigerant over the entire precipitation region is preferably in the above range.

  Note that “the flow rate of the refrigerant at the maximum calorific value” means, for example, the flow rate P in FIG.

  Furthermore, in this embodiment, since the heat loss in the initial stage of precipitation is small, the temperature inside the reactor in the initial stage of precipitation becomes higher than that in the conventional case, so the growth rate of the rod is increased. Thereby, as shown in FIG. 4, the time required for manufacturing a rod of a predetermined size can be shortened compared to the conventional case, and as a result, productivity is improved. Moreover, shortening the time required for the production of the rod also contributes to the reduction of the power consumption.

  Further, an oxide film is formed on the surface of the core wire before energization, but it is preferable that the oxide film is removed from the viewpoint of quality. According to the present embodiment, as described above, the temperature inside the reactor at the initial stage of deposition becomes higher than the conventional temperature, so that an excellent removal action of the oxide film can be obtained by making the inside of the reactor a hydrogen atmosphere. it can.

Thus, according to the method for manufacturing a polycrystalline silicon rod of the present embodiment, the power consumption can be reduced and the productivity can be improved. Note that the flow rate of the refrigerant up to at least 50% of the maximum calorific value in the silicon precipitation reaction is as follows: the inlet refrigerant temperature T1 at the refrigerant supply port 15, the outlet refrigerant temperature T2 at the refrigerant discharge port 17, and the specific heat C of the refrigerant. Are preferably adjusted so as to satisfy the relationship of (T2−T1) × C ≧ 9 cal / g, and more preferably satisfy the relationship of 10 cal / g ≦ (T2−T1) × C ≦ 50 cal / g. More preferably, it is adjusted so as to satisfy the relationship of 20 cal / g ≦ (T2−T1) ≦ 40 cal / g. By setting (T2−T1) × C within this range, it is possible to reduce power intensity and improve productivity while keeping driving safety more.
In general, (T2-T1) × C is set to 10 to 45 cal / g at the end of the precipitation that reaches the maximum calorific value because of the necessity of preventing deterioration of the reactor.

  In the present embodiment, it is preferable that (T2−T1) × C during energization is constant within a predetermined range. Thereby, the fluctuation | variation of a refrigerant | coolant supply amount can be suppressed low. Within the predetermined range, the difference between the maximum value and the minimum value of (T2−T1) × C during energization is preferably 4 to 10 cal / g.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, in the embodiment described above, the cooling passage 9 is one passage through which the cover 4 flows after flowing through the bottom plate 6, but as another embodiment of the present invention, as shown in FIG. May be divided into two routes: a route through the cover 4 and a route through the bottom plate 6. In the case of FIG. 5, the inlet refrigerant temperature T1a of the cover 4 is a temperature detected by the temperature detector 50a, and the outlet refrigerant temperature T2a is a temperature detected by the temperature detector 52a. Further, the inlet refrigerant temperature T1b of the substrate 6 is a temperature detected by the temperature detector 50b, and the outlet refrigerant temperature T2b is a temperature detected by the temperature detector 52b. Even in this case, by adjusting the flow rate of the refrigerant to reach at least 50% of the maximum heat generation amount in the silicon precipitation reaction, the power consumption rate can be reduced by adjusting it to be smaller than the flow rate of the refrigerant at the maximum heat generation amount. It can be reduced and productivity can be improved.

  Further, each of the cover 4 and the bottom plate 6 may be provided with a plurality of cooling passages. In this case, in each cooling passage, the flow rate of the refrigerant up to at least 50% of the maximum heat generation amount in the silicon precipitation reaction is adjusted to be smaller than the flow rate of the refrigerant in the maximum heat generation amount. Thus, the above effect can be obtained.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Examples 1-4
In a reactor 2 with 10 rods (inverted U-shaped 5 pairs) standing up, a 2000 mm high inverted U-shaped silicon core wire 10 is energized and heated to about 1000 ° C., and at the same time, a raw material for silicon deposition Gas (mixed gas of trichlorosilane and hydrogen) is supplied to the reactor 2, and the polycrystalline silicon is cooled to a diameter of 120mm while cooling the reactor 2 with the refrigerant flowing through the cooling passages provided in the cover 4 and the bottom plate 6. Precipitated. The material of the reactor 2 was stainless steel (SUS).

The refrigerant was water, the specific heat was 1 cal / g · ° C., and the inlet refrigerant temperature T1 was 30 ° C. in all the cooling passages. The maximum calorific value in this silicon precipitation reaction was predicted to be 884 kW from the above prediction formula. The maximum flow rate corresponding to the maximum calorific value was determined as a flow rate 1.1 times that in the cooling passage because the minimum flow rate at which the inner wall temperature of the reactor did not exceed 300 ° C. was determined as 30.4 m ³ / h. .

In all the cooling passages, the flow rate of the refrigerant up to 50% of the maximum heat generation amount in the silicon precipitation reaction is set to the initial flow rate shown in Table 1 at the time of starting the precipitation, and is 50% of the maximum heat generation amount. At a certain rate so as to be 1.1 times the maximum flow rate, and thereafter the refrigerant was supplied at the same flow rate until the completion of the precipitation reaction. Further, Table 1 also shows the average flow rate of the refrigerant up to 50% of the maximum calorific value when the flow rate of the refrigerant at the maximum calorific value is 1.

  Further, (T2−T1) × C is the value shown in Table 1 at the start of precipitation, and then increased at a constant rate. At the end of the precipitation reaching the maximum calorific value, (T2−T1) × C was 25 cal / g.

  After the rod grows to the diameter, the supply of the reaction gas is stopped and the waste gas is exhausted from the reaction chamber to complete the precipitation, and then the annealing is continued at 1050 ° C. for 1 hour. The power supply to was stopped. Thereafter, the cover 4 was opened and the rod 20 was taken out.

  About the obtained rod, the production amount per unit time (productivity) and the electric power basic unit were calculated. The results are shown in Table 1.

Comparative Example 1
In Example 1, polycrystalline silicon was deposited in the same manner as in Example 1 except that the flow rate of the refrigerant was set to the maximum flow rate in all the cooling passages from the start of energization to the end of energization. Note that (T2−T1) × C is 2 cal / g at the start of precipitation, and then increased at a constant rate. At the end of the precipitation reaching the maximum calorific value, (T2−T1) × C was 25 cal / g. The results are shown in Table 1.

Examples 5-8
In Example 1, the period for adjusting the refrigerant flow rate to be smaller than the refrigerant flow rate at the maximum calorific value is 70% of the maximum calorific value in the silicon precipitation reaction, and the maximum calorific value. At the end of the precipitation to reach, the same polycrystalline silicon was precipitated except that (T2-T1) × C was 28 cal / g. The results are shown in Table 2.

  When the average flow rate of the refrigerant up to 50% of the maximum calorific value in the silicon precipitation reaction is smaller than the flow rate of the refrigerant at the maximum calorific value in the silicon precipitation reaction (Examples 1 to 4), When the average flow rate of the refrigerant up to 70% of the maximum heat generation amount in the precipitation reaction is smaller than the flow rate of the refrigerant at the maximum heat generation amount in the silicon precipitation reaction (Examples 5 to 8), It was confirmed that the power consumption rate was lower than when the flow rate was constant (Comparative Example 1).

DESCRIPTION OF SYMBOLS 2 ... Reactor 4 ... Cover 401 ... Cover inner surface 402 ... Cover outer surface 6 ... Bottom plate 8 ... Window member 9 ... Cooling passage 10 ... Core wire 12 ... Electrode 14 ... Source gas supply port 16 ... Source gas discharge port 15, 15a, 15b ... Refrigerant supply port 17, 17a, 17b ... Refrigerant discharge port 20 ... Rod 30 ... Electric power supply means 32 ... Control device 38 ... Non-contact thermometer 42, 42a, 42b ... Refrigerant flow rate control unit 50, 50a, 50b , 52, 52a, 52b ... temperature detector

Claims (3)

A reactor having at least one pair of electrodes for energizing the silicon core wire and having a cooling passage for cooling the inner wall by circulating a refrigerant having a temperature equal to or lower than the boiling point under atmospheric pressure is used. A method for producing a polycrystalline silicon rod, wherein a silicon deposition source gas is supplied into the reactor while a core wire is connected and energized, and polycrystalline silicon is deposited on the silicon core wire,
The production amount of polycrystalline silicon rods per reactor is an average of 20 kg / hour or more, and circulates through the cooling passage up to a calorific value of at least 50% of the maximum calorific value in the silicon precipitation reaction. A method for producing a polycrystalline silicon rod, wherein the flow rate of the refrigerant is adjusted to be smaller than the flow rate of the refrigerant at the maximum calorific value. The temperature of the refrigerant at the inlet of the cooling passage to the reactor is T1,
T2 is the temperature of the refrigerant at the outlet of the cooling passage from the reactor,
When the specific heat of the refrigerant is C,
The flow rate of the refrigerant flowing through the cooling passage up to a calorific value of at least 50% of the maximum calorific value in the silicon precipitation reaction is such that T1 and T2 are (T2−T1) × C ≧ 9 cal / g. It adjusts so that Formula may be satisfy | filled, The manufacturing method of the polycrystalline silicon rod of Claim 1 characterized by the above-mentioned.   A bottom plate provided with at least one pair of electrodes for energizing the silicon core wire, and a cover that covers the bottom plate, and at least a part of the wall constituted by the bottom plate and the cover circulates the coolant to the inner wall. An apparatus for manufacturing a silicon rod, comprising: a reactor having a double structure that forms a cooling passage for cooling; and a flow rate adjusting means for adjusting a flow rate of the refrigerant flowing through the cooling passage.

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