JP4038110B2 - Method for producing silicon - Google Patents

Description

【表２】

【表３】

上記比較例より、シリコン析出を融点以下の温度、特に従来のシーメンス法で実施する場合、多量の余剰ＳＴＣが生成することが理解される。
【０１０７】
また、実施例４との比較において理解されるように、同規模の設備でもシリコン生産量は実施例４の方が約４倍多くなっており、本発明による方法は極めて優れた経済性をもつことがわかる。
【図面の簡単な説明】
【図１】本発明の方法の実施に好適に使用されるシリコン析出のための装置の概略図
【図２】本発明の方法の実施に好適に使用される他のシリコン析出のための装置の概略図
【図３】析出温度におけるＳＴＣと塩化水素との生成量の傾向を示すグラフ
【図４】本発明の代表的な態様を示す工程図
【図５】本発明の他の代表的な態様を示す工程図
【符号の説明】
１ 筒状容器
３ 加熱装置
４ クロロシラン類供給管
５ シールガス供給管
６ シールガス供給管
７ 密閉容器
８ シリコン
９ 冷却材
１１ シールガス供給管１１
１２ 取出配管
１５ 空間
１６ 加熱手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel method for producing silicon. Specifically, in the silicon production method by reaction of trichlorosilane (hereinafter also referred to as TCS) and hydrogen, the treatment of tetrachlorosilane (hereinafter also referred to as STC) generated by silicon deposition reaction is extremely advantageous industrially. A silicon manufacturing method that can be performed is provided.
[0002]
[Prior art]
High-purity silicon using TCS as a raw material can be produced by a reaction between TCS and hydrogen. Industrially, a so-called Siemens method is known in which a polycrystalline silicon rod is obtained by heating the surface of a rod and supplying TCS together with hydrogen to deposit silicon on the rod to grow.
[0003]
In order to stably deposit silicon, the above precipitation reaction is usually performed at a temperature of 900 to 1250 ° C., substantially 900 to 1150 ° C., and STC and hydrogen chloride are accompanied by the precipitation reaction. By-product.
[0004]
Under the temperature employed in the Siemens method, STC and hydrogen chloride are generated in an overwhelmingly large amount of STC and hydrogen chloride generated by the silicon precipitation reaction.
[0005]
Incidentally, in the Siemens method, when 1 t of high-purity silicon is produced, STC is produced in an amount of 15 to 25 t, whereas hydrogen chloride is produced in an amount of about 0.1 to 1 t.
[0006]
STC by-produced by such silicon deposition reaction is a chemically very stable compound as compared with TCS, and as shown in the following reaction formula, the rate of silicon deposition reaction decreases as the ratio of STC mixed into TCS increases. In addition to this, the efficiency of the silicon precipitation reaction is significantly reduced due to the addition of equilibrium inhibiting factors.
[0007]
・ Delayed deposition rate
TCS + H ₂ → Si + HCl + DCS + TCS + STC (1)
STC + H ₂ → Si + HCl + DCS + TCS + STC (2)
(In the formula, DCS represents dichlorosilane.)
The Si yield under the same reaction conditions is as follows: Formula (1): Formula (2) = 5: 1
・ Equilibrium inhibition
TCS + H ₂ → Si + HCl + DCS + TCS + STC
In the above formula, when the production system STC is present in the raw material system, the equilibrium is biased to the left.
(Le Chatelier principle)
For this reason, in a facility for industrially performing silicon deposition reaction, part or all of the STC generated in large quantities during the silicon deposition reaction must be discharged to a nearby or remote processing facility (hereinafter referred to as STC processing facility). It was the present situation that we did not get.
[0008]
Examples of the STC processing equipment include equipment for producing fumed silica and quartz by hydrolyzing STC with an oxyhydrogen flame, or epitaxial equipment such as a silicon wafer.
[0009]
However, the amount of STC consumed in the STC processing facility depends on the amount of demand for fumed silica or the like that uses the STC as a raw material, and if those demands decrease, it is necessary to discard excess STC that cannot be processed. . As described above, the production of silicon and the demand for STC are based on a delicate balance, and a fundamental solution has not yet been achieved in the measures for STC generated in large quantities.
[0010]
In order to solve the above problem, a closed system has been proposed as a self-supporting process that reduces the amount of STC generated and does not discharge STC (see Patent Document 1 and Patent Document 2). However, any of these methods can be realized only on an ideal system. For example, the method described in Patent Document 1 specifies a closed technology that suppresses STC by-product by specifying a gas composition to be used for silicon deposition and precipitating silicon at a deposition temperature of 900 to 1250 ° C. As shown in the examples, by adjusting the amount of gas supplied to be extremely small relative to the reaction area, the silicon precipitation reaction system is adjusted to a condition close to an equilibrium state (ideal system). ing. Such conditions make it difficult to ensure an industrially effective production amount. Moreover, when the supply amount of the raw material gas having the above composition is increased in order to secure the production amount, the TCS reaction rate is remarkably lowered, and industrial implementation is difficult.
[0011]
In order to carry out the production of silicon at the above deposition temperature with an industrially advantageous production amount, the ratio of hydrogen in the gas composition must be reduced to improve the TCS reaction rate, and accordingly the STC. The amount of by-product increases rapidly.
[0012]
Therefore, in order to industrially perform silicon deposition at a relatively low temperature of 1250 ° C. or lower, as described above, a large amount of STC by-product is required, and the technology for industrially implementing a closed system is as follows. The current situation has not yet been completed.
[0013]
In addition, as a process of manufacturing TCS from STC, STC is converted into TCS by hydrogen reduction, and then TCS is reacted by reacting hydrogen chloride of the reaction gas with metallurgical grade silicon, which is low-purity silicon of metallurgical grade. Although a method for obtaining this has been proposed (see Patent Document 3), as described above, the present situation is that the problem in the process in which the STC generation ratio is overwhelmingly large has not been solved.
[0014]
On the other hand, various methods for carrying out the silicon precipitation reaction at around 1410 ° C., which is the melting point of silicon, have been proposed (see, for example, Patent Document 4), but research on the gas composition at such a precipitation temperature has not been conducted. Needless to say, the present situation is that no study has been made on industrial processes.
[Patent Document 1]
JP-A-52-133022
[Patent Document 2]
JP-A-10-287413
[Patent Document 3]
JP-A-57-156318
[Patent Document 4]
Japanese Patent Laid-Open No. 11-314996
[Problems to be solved by the invention]
Accordingly, a first object of the present invention is to provide a silicon manufacturing technique in which the production efficiency of TCS is improved while securing an industrially advantageous production amount and keeping the amount of by-produced STC low. It is in.
[0015]
A second object of the present invention is to provide a self-supporting silicon manufacturing process that does not require a large reduction device for the by-product STC and can be closed.
[0016]
In addition, the third object of the present invention is to easily control the amount of by-product STC, and when an STC processing facility is additionally provided, silicon capable of arbitrarily adjusting the amount of STC supplied to the processing facility. It is to provide manufacturing technology.
[0017]
[Means for Solving the Problems]
The inventors of the present invention have made extensive studies to achieve the above object. As a result, the amount of STC produced is considered by the Siemens method by carrying out the precipitation reaction of silicon using TCS and hydrogen as raw materials in a specific high-temperature range that has not been industrially performed conventionally. It has been found that it is possible to construct an industrial process that has been suppressed to a very small amount.
[0018]
That is, the first object of the present invention is to make a silicon deposition process in which trichlorosilane and hydrogen are reacted at a temperature of 1300 ° C. or more to produce silicon, and to bring the gas after the reaction in the silicon deposition process into contact with the raw material silicon. The trichlorosilane is produced by the reaction of hydrogen chloride and silicon contained in the exhaust gas to produce trichlorosilane, and the trichlorosilane is separated from the gas after the reaction in the trichlorosilane production process and circulated to the silicon deposition process. This is achieved by a silicon production method characterized by comprising a first circulation step of trichlorosilane.
[0019]
Further, since the amount of the STC produced as a by-product was extremely small, it was found that the STC could be closed without substantially taking it out of the process by reducing it with hydrogen.
[0020]
That is, a second object of the present invention is a silicon deposition step in which trichlorosilane and hydrogen are reacted at a temperature of 1300 ° C. or more at a molar ratio of hydrogen to trichlorosilane of 10 or more to produce silicon, A trichlorosilane generation step in which a gas after reaction in the silicon deposition step is brought into contact with the raw material silicon to generate trichlorosilane by reaction of hydrogen chloride contained in the exhaust gas with silicon, after the reaction in the trichlorosilane generation step The trichlorosilane is separated from the gas and the tetrachlorosilane in the remaining components after the trichlorosilane separation in the trichlorosilane first circulation step and the trichlorosilane first circulation step is circulated to the silicon deposition step to obtain trichlorosilane. Tetrachlorosilane reduction step and the tetrachlorosilane Achieved the gas after the reaction in the emission reduction process by the manufacturing method of the silicon, characterized in that consisting of trichlorosilane second circulating step circulating in the trichlorosilane forming step.
[0021]
Furthermore, the inventors of the present invention have made it possible to change the molar ratio of hydrogen to TCS in the above-described silicon precipitation reaction at a high temperature range without affecting the quality of the obtained silicon, and in a very wide range. It was found that the amount of raw material can be adjusted, whereby the amount of STC supplied to the facility can be easily controlled even when the STC processing facility is installed.
[0022]
Accordingly, a third object of the present invention is to make a silicon precipitation step in which trichlorosilane and hydrogen are reacted at a temperature of 1300 ° C. or more to produce silicon, and to bring the gas after the reaction in the silicon precipitation step into contact with the raw material silicon. Then, trichlorosilane is produced by the reaction of hydrogen chloride contained in the exhaust gas with silicon and trichlorosilane is produced, and the trichlorosilane is separated from the gas after the reaction in the trichlorosilane production process and circulated to the silicon deposition process. In the trichlorosilane first circulation step, a tetrachlorosilane reduction step in which a part of tetrachlorosilane in the remaining components after trichlorosilane separation in the trichlorosilane first circulation step is reduced with hydrogen to obtain trichlorosilane, in the tetrachlorosilane reduction step The gas after the reaction produces the trichlorosilane Trichlorosilane that has a tetrachlorosilane extraction step that takes out the remainder of the tetrachlorosilane that is supplied to the second circulation step and the tetrachlorosilane reduction step that is circulated and supplies it to the tetrachlorosilane treatment facility, and that is supplied to the silicon deposition step This is achieved by a method for producing silicon characterized by adjusting the amount of extraction by changing the molar ratio of hydrogen to hydrogen.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, in the silicon deposition step, TCS and hydrogen are heated to 1300 ° C. or higher, preferably 1300 to 1700 ° C., more preferably 1350 to 1700 ° C., most preferably higher than the melting point of silicon and 1700 ° C. or lower. This is a step of generating silicon by reacting at a temperature.
[0024]
The method for industrially continuously depositing silicon in the high temperature region is not particularly limited, but a method using the apparatus shown in FIG. 1 is suitable. That is, (1) a cylindrical container 1 having an opening 2 serving as a silicon outlet at the lower end, and (2) heating the inner wall from the lower end of the cylindrical container 1 to an arbitrary height to a temperature equal to or higher than the melting point of silicon. (3) Supply of chlorosilanes that supply chlorosilanes A provided in the cylindrical container so as to open downward in a space 5 surrounded by an inner wall heated to 1300 ° C. or higher. The pipe 4, (4) a seal gas supply pipe 6 for supplying hydrogen gas as a seal gas B in a gap formed by the inner wall of the cylindrical container and the outer wall of the chlorosilane supply pipe, and (5) the cylindrical container 1 A device basically composed of a coolant 9 provided with a space below is provided.
[0025]
In the said apparatus, in order to collect | recover the exhaust gas discharged | emitted from the cylindrical container 1 efficiently, it is preferable to cover the cylindrical container 1 and the coolant 9 with the airtight container 7 which provided the exhaust pipe 12 of the exhaust gas D. FIG.
[0026]
At that time, a seal gas supply pipe 11 is provided in a gap formed by the outer wall of the cylindrical container 1 and the inner wall of the sealed container 7 to supply a seal gas C such as nitrogen, hydrogen, and argon. preferable.
[0027]
Moreover, in the said apparatus, the high frequency coil is used suitably for the heating apparatus 3 for heating the cylindrical container 1. FIG. Moreover, the material of the cylindrical container 1 is preferably a material that can be heated by a high frequency and is resistant at the melting point of silicon, and generally carbon is preferably used. In addition, it is more preferable that the surface of the carbon is coated with silicon carbide, pyrolytic carbon, boron nitride or the like in order to achieve improved durability of the cylindrical container and improved purity of the silicon product.
[0028]
In the said apparatus, the chlorosilane supplied from the chlorosilanes supply pipe 4 may be mixed with hydrogen. The chlorosilane gas or the mixed gas of chlorosilane and hydrogen is supplied to the space 5 of the cylindrical container 1 together with the hydrogen of the seal gas supplied from the seal gas supply pipe 6, and silicon is deposited on the inner wall by the heating device 3.
[0029]
When the cylindrical container 1 is heated above the melting point of silicon, the deposited silicon becomes a silicon melt on the inner wall of the cylindrical container, flows down the inner wall, and spontaneously falls as a droplet 14 from the opening 2. Therefore, the inside of the cylindrical container can always be kept in the initial state without performing a periodic temperature raising operation.
[0030]
In addition, when the cylindrical container 1 is heated to a temperature of 1300 ° C. or higher and lower than the melting point of silicon, silicon precipitates as a solid, but when a certain amount of precipitation is reached, the heating output is increased or gas supply is performed. Precipitation can be continuously performed by reducing the amount, raising the cylindrical container to a temperature equal to or higher than the melting temperature of silicon, melting part or all of the precipitate, and dropping and collecting the precipitate.
[0031]
That is, in this specification, since the reaction between TCS and hydrogen occurs on the precipitation surface of the cylindrical container, the temperature of the reaction corresponds to the heating temperature of the cylindrical container.
[0032]
In addition, when the cylindrical container 1 is heated near the melting point of silicon, there are some cases where a part that is precipitated in a solid state and a part that is precipitated in a molten state are mixed. When the temperature reaches the temperature, the temperature is increased, and a part or all of the solid is melted and recovered by dropping.
[0033]
The droplets of the silicon melt falling from the cylindrical container or the partially melted solid silicon are dropped on the coolant 9 as a receiving tray below, and solidified and recovered.
[0034]
In the case of dropping the silicon as a melt, the silicon melt may be refined by a known method when the silicon falling material is received in the coolant 9 or during the dropping before the silicon is received.
[0035]
The silicon precipitate that has fallen into the coolant 9 and solidified can be taken out after the precipitation reaction is stopped, and more preferably, the silicon precipitate is taken out while continuing the precipitation reaction. As a specific method for carrying out the recovery while continuing the reaction, the temperature of the cylindrical container 1 is temporarily adjusted to 1300 ° C. or higher and lower than the melting point to prevent the silicon melt from falling, and the precipitation reactor and the recovery container By closing the valve installed between them and opening the recovery part, or by the crushing device installed in the recovery part, the silicon precipitate solidified in the recovery part is given a mechanical force and pulverized to some extent, Further, there is a method of intermittently taking out silicon E from the silicon take-out port 13 located at the lower part.
[0036]
Further, in the reaction apparatus shown in FIG. 1 described above, the mode in which the raw material gas is supplied to the inner surface of the cylindrical container has been shown. However, as shown in FIG. 2, the cylindrical container 1 has a multiple structure in which the lower part is opened. A reaction apparatus in which the raw material gas A is supplied to the space 15 formed between the cylinders from above can also be suitably used.
[0037]
However, when the apparatus shown in FIG. 2 is used, it is recommended that the reaction temperature is set to be equal to or higher than the melting point in order to prevent the space from being blocked due to silicon deposition.
[0038]
In addition, it is particularly preferable to provide heating means 16 such as a high-frequency generating coil and an electric heater (not shown) in the central space of the multiple cylindrical containers so that the inner cylindrical container can be heated sufficiently. . In this case, it is preferable that the space in which the heating unit 16 is provided has an inert gas as a sealed space. The sealed space may be in a vacuum state. Furthermore, a heat insulating material (not shown) for protecting the heating means 16 may be provided.
[0039]
In the method of the present invention, when the reaction temperature is 1300 ° C. or higher, the amount of STC generated in the silicon deposition step is effectively reduced, and the amount of hydrogen chloride that is easier to generate TCS than the STC is increased. It is necessary to make it.
[0040]
FIG. 3 shows the tendency of STC by-product and hydrogen chloride by-product at temperatures of 1050 ° C., 1150 ° C., 1350 ° C., and 1450 ° C. in the reaction when the molar ratio of hydrogen to TCS is 10. It is a thing. As understood from FIG. 3, when the temperature exceeds 1300 ° C. as a boundary, it is understood that the by-product amount of STC is remarkably reduced and the by-product amount of hydrogen chloride is increased.
[0041]
Although the reason why the reaction result of the precipitation reaction temperature of 1300 ° C. or higher and the conventionally proposed reaction result of 1250 ° C. or lower is different as described above has not been clarified yet, the temperature of the boundary film near the precipitation surface is deeply involved. It is presumed that
[0042]
That is, the supplied TCS is sufficiently activated in the high-temperature film and the conversion rate to silicon is increased, but the activation of TCS is somewhat insufficient in the low-temperature film. This is presumably due to the fact that the TCS of the molecule tends to stop in the reaction that disproportionates to dichlorosilane and STC. In fact, the precipitation reaction carried out at the temperature of the present invention has resulted in significantly less dichlorosilane formation than the conventional Siemens process.
[0043]
In the examination process of the present invention, it was clarified that the precipitation reaction temperature that sufficiently achieves the object of the present invention is 1300 ° C. or higher. By the way, by performing the silicon precipitation reaction at the above temperature, the amount of STC produced can be reduced to 1/2 or less, or in some cases to 1/3 of the conventional Siemens method. At the same time, the amount of hydrogen chloride produced can be increased to 5 times or more, or in some cases 10 times that of the Siemens process. In addition, the silicon deposition rate can be increased to 5 times or more, or in some cases 10 times that of the Siemens method, and the reaction rate of the raw material TCS can be increased to 1.5 times or more, or in some cases, 2 times that of the Siemens method. Therefore, a large amount of silicon can be produced with a very small deposition reactor.
[0044]
In addition, the ratio of TCS and hydrogen subjected to the above reaction is expressed as the molar ratio of hydrogen to TCS (H ₂ / TCS) is preferably adjusted to 10 or more, preferably 15 to 30 in order to more effectively reduce the amount of STC produced in the silicon deposition step, while also significantly increasing the amount of hydrogen chloride produced. .
[0045]
Furthermore, the pressure of the reaction is not particularly limited, but is preferably a pressure equal to or higher than normal pressure.
[0046]
In the present invention, the TCS generation step is a step in which the gas after the reaction in the silicon deposition step is brought into contact with the raw material silicon, and TCS is produced by the reaction between hydrogen chloride contained in the gas and silicon.
[0047]
In the gas after the reaction in the silicon deposition step, hydrogen chloride and STC are mainly used as products, and a small amount of dichlorosilane (hereinafter also referred to as DCS), multimers of chlorosilanes, and the like are present. Unreacted TCS is also included. By bringing these mixed gases into contact with the raw material silicon, hydrogen chloride selectively reacts to generate TCS. Such a reaction is an exothermic reaction, and TCS can be produced extremely advantageously in terms of energy compared to an endothermic reaction in which STC is produced by reducing STC with hydrogen.
[0048]
As said raw material silicon, the well-known metallurgical grade silicon generally used as a raw material for manufacture of silicon is used without a restriction | limiting in particular.
[0049]
In addition, as the reactor used for the above reaction, an apparatus capable of contacting the raw material silicon and the precipitation reaction exhaust gas is used without particular limitation. For example, a fluidized bed reactor that reacts gas and powder while fluidizing raw silicon powder with gas is suitable in industrial implementation. At this time, as a method for adjusting the temperature of the fluidized bed reactor, a known method can be used without limitation. For example, a method of installing a heat exchanger inside or outside the fluidized bed or adjusting the temperature of the preheating gas can be mentioned.
[0050]
In the trichlorosilane production step, the temperature at which silicon and hydrogen chloride start to react is approximately 250 ° C. Therefore, the reaction temperature needs to be 250 ° C. or higher. Moreover, in order to improve the yield of TCS, it is preferable to carry out at the temperature of 400 degrees C or less. In particular, in order to maintain the reaction stably industrially, the reaction temperature is preferably adjusted at 280 to 350 ° C.
[0051]
The reaction temperature in the trichlorosilane production step may vary depending on the concentration of hydrogen chloride supplied. For example, if there is any variation in reaction conditions in the silicon deposition process, the concentration of hydrogen chloride generated in the process also varies. And if hydrogen chloride concentration fluctuates, the reaction calorific value in a trichlorosilane production process will change, and reaction temperature will also change.
[0052]
In order to prevent such fluctuation due to the hydrogen chloride concentration, it is preferable to adjust the hydrogen chloride concentration to be constant while monitoring the hydrogen chloride concentration in the gas flowing into the silicon production process. The method for adjusting the hydrogen chloride concentration is not particularly limited, but a mode in which new hydrogen chloride is supplied into the gas flowing into the silicon production step and the supply amount is adjusted is preferable.
[0053]
The hydrogen chloride concentration can be measured by gas chromatography, infrared absorption method, etc., but the method using infrared absorption method outputs the analysis result as an electrical signal to the outside while performing analysis in a very short time. This is more preferable because the hydrogen chloride concentration can be adjusted automatically.
[0054]
In the present invention, the reacted gas obtained from the TCS generation step is sent to the TCS first circulation step, where the TCS contained in the gas is separated and circulated to the silicon deposition step. Among them, it is preferable to remove a part of chlorosilanes from the gas in advance for hydrogen circulating in the silicon deposition step. Various known methods can be used for separating hydrogen and chlorosilanes, but industrially, it can be easily achieved by cooling the gas.
[0055]
As a method for cooling the gas, it is possible to simply pass it through a cooled heat exchanger, or it is possible to employ a method in which the gas is cooled by a condensed and cooled condensate. These methods can be employed alone or in combination.
[0056]
The cooling temperature may be any temperature as long as a part of the chlorosilanes is condensed, but is 10 ° C. or less, more preferably −10 ° C. or less, and most preferably for achieving high purity of hydrogen. -30 degrees C or less is good. Thus, by removing a part of the chlorosilanes, impurities such as heavy metals, phosphorus, boron, etc. contained in the raw silicon can be removed from hydrogen, and the deposited silicon can be highly purified. it can.
[0057]
Some of the chlorosilanes are separated and the recovered hydrogen is sufficiently high in purity, but may contain a little more boron compound depending on the separation conditions. Therefore, it is desirable to remove the boron compound from the hydrogen gas according to the required purity of the silicon product. The method for removing the boron compound is not particularly limited, but —NR ₂ (Where R is an alkyl group having 1 to 10 carbon atoms), -SO ₃ A method in which a substance having a functional group such as H, —COOH, and —OH is brought into contact with the hydrogen gas is preferable. Most simply, ion exchange resins having these functional groups can be used.
[0058]
For separation of TCS from the gas after TCS generation, a known method is employed without any particular limitation. For example, when separating the hydrogen, the TCS can be separated by distilling and purifying the condensed gas. Further, the residual components after separation of TCS by such distillation purification are a small amount of DCS as a light end, STC as a heavy end and a multimeric component of a small amount of chlorosilanes and a heavy metal compound.
[0059]
The light end need not be separated from TCS in particular, but when separated, it can be supplied together with STC in the STC reduction reaction, or gasified and supplied again to TCS generation step 102. In addition, since the heavy end is mainly composed of STC, STC and heavy metal compound are separated by a known method, and then STC is converted into TCS by a reduction process described later, or is processed in another processing process. Can be used effectively.
[0060]
When it is necessary to further remove the boron compound from the chlorosilane recovered as a liquid according to the required purity of the silicon product, after contacting the chlorosilanes with the solid or liquid compound having the functional group described above, This is accomplished by distillation purification as necessary.
[0061]
The remaining components obtained by separating and collecting most of the STC from the heavy end are generally neutralized and discarded. In this case, with respect to chlorine that is lost along with this, the loss can be replenished into the system by hydrogen chloride or chlorosilanes.
[0062]
In addition, closed in this invention includes the aspect which replenishes the said inevitably decreasing chlorine.
[0063]
In the present invention, in order to circulate the gas, a driving force to circulate is required, but a known type of gas pressurizer for generating the driving force can be adopted. The gas pressurizer is installed either upstream of the TCS generation process that can reduce the size of the TCS generation process or the hydrogen and chlorosilane separation process, or the silicon precipitation process with the least amount of substances that can cause troubles in the pressurizer. The upstream side is more preferable.
[0064]
The silicon production method of the present invention employs a step of performing a silicon precipitation reaction at 1300 ° C. or higher, and adjusts the molar ratio of hydrogen to TCS in the precipitation reaction, thereby providing a synergistic effect thereof. The amount of STC produced in the reaction can be reduced to an extremely small amount of 1/4, or in some cases, 1/5 of the conventional Siemens method.
[0065]
Therefore, in the present invention, a silicon manufacturing method using a closed system in which the entire amount of STC generated in the silicon deposition step is returned to the TCS and reused can be realized very advantageously. In addition, due to the high reaction rate of TCS and the high yield of silicon, the size of each device for gas circulation is about 1/2 or less than that of the Siemens method. can do.
[0066]
FIG. 4 is a process diagram showing a silicon manufacturing method using the closed system. As shown in the figure, such a method includes a silicon deposition step 101 in which TCS and hydrogen are reacted at a temperature in which the molar ratio of hydrogen to TCS is 10 or more and 1300 ° C. or more to generate silicon, A gas after reaction in the TCS generation process, a TCS generation process 102 in which a gas after reaction in the silicon deposition process is brought into contact with the raw material silicon to generate TCS by a reaction between hydrogen chloride contained in the exhaust gas and silicon; The TCS first circulation step 103 for separating the TCS from the silicon deposition step, the STC reduction step 104 for obtaining the TCS by reducing the STC in the remaining components after the TCS separation in the TCS first circulation step with hydrogen, and the STC It comprises a TCS second circulation step 105 for circulating the gas after the reaction in the reduction step to the TCS generation step.
[0067]
After the TCS generation step 102, it is preferable to provide a hydrogen / trichlorosilane separation step 201 for separating hydrogen and chlorosilanes by condensation as described above. Further, in the TCS first circulation step 103, the TCS separation employs a distillation purification step 202 for purifying the coagulated liquid from the hydrogen / trichlorosilane separation step 201 by distillation.
[0068]
In the above aspect, as described above, the STC reduction step is a step of separating the hydrogen as necessary and then reacting STC in the remaining components after separation of TCS with hydrogen to convert it into TCS. As the reaction conditions, known conditions are employed without particular limitation, but in order to increase the conversion rate to TCS and improve the conversion amount from STC to TCS, the reduction reaction temperature is 1300 ° C. or higher, preferably It is preferable to adjust to 1300-1700 degreeC, Most preferably, it is adjusted to 1410-1700 degreeC. At this time, when the reduction reaction temperature is lower than 1410 ° C., that is, lower than the melting point of silicon, it is possible to suppress the precipitation of solid silicon in the reactor by adjusting the molar ratio of hydrogen to STC to be supplied to 10 or less. . When the reduction reaction temperature is 1410 ° C. or higher, even if the silicon is deposited, the precipitate is melted and discharged out of the system. Therefore, the molar ratio of STC and hydrogen is not particularly limited. Can be adjusted.
[0069]
In addition, the structure of the reaction apparatus used for the reaction is not particularly limited as long as the reaction temperature condition can be achieved, but the apparatus shown in FIG. 1 or 2 used in the silicon precipitation reaction is also used. It is preferable to divert to use in a reduction reaction apparatus. That is, STC is supplied from the chlorosilane supply pipe 4.
[0070]
In the present invention, the TCS second circulation step 105 is a step in which the gas after the reaction in the STC reduction step 104 is circulated to the TCS generation step 102 and the contained hydrogen chloride is reacted with the raw material silicon. Here, the present inventors have found that the compositions of the silicon deposition reaction exhaust gas and the STC reduction reaction exhaust gas are very similar under the conditions shown in the present invention. That is, in the TCS generation step 102, each exhaust gas can be treated separately using a plurality of reactors, or both reaction exhaust gases can be treated together using the same reactor.
[0071]
In the silicon production method of the present invention, in addition to the advantages of performing the above-described silicon deposition at a temperature of 1300 ° C. or higher, TCS and hydrogen can be used in the process without changing the quality of silicon obtained from the silicon deposition process. By changing the molar ratio, there is an advantage that the amount of STC to be generated can be arbitrarily adjusted in a wide range from the extremely small amount described above to an amount equivalent to the conventional Siemens method.
[0072]
That is, in the conventional Siemens method, the molar ratio of hydrogen to TCS is controlled under the condition of being almost fixed to 5 to 10, and when the molar ratio changes during precipitation, the shape and surface state of the precipitate Not only will the product become extremely deteriorated and its value as a product will be reduced, but also a severe temperature distribution may occur partially during the precipitation, resulting in a state where it is difficult to continue further precipitation. Are known. Therefore, a large manipulation of the molar ratio is practically impossible industrially.
[0073]
In contrast, since the silicon production method of the present invention deposits silicon at a high temperature close to the melting temperature of 1300 ° C., silicon is deposited in a partially molten state or at a temperature higher than the melting point. In this case, the precipitation reaction proceeds in a state where the whole is melted. In the recovery, part or all of the precipitate is melted and recovered from the heating body.
[0074]
Therefore, even if a part of the precipitation surface melts due to the change in the molar ratio, there is essentially no need to consider the shape and surface state of the precipitate. The molar ratio of can be arbitrarily adjusted.
[0075]
That is, in the present invention, as shown in the process diagram of FIG. 5, a silicon deposition step 101 in which trichlorosilane and hydrogen are reacted at a temperature of 1300 ° C. or more to produce silicon, and after the reaction in the silicon deposition step. A trichlorosilane generation step 102 in which a gas is brought into contact with raw material silicon to generate trichlorosilane by reaction of hydrogen chloride contained in the exhaust gas with silicon, and trichlorosilane is separated from the gas after the reaction in the trichlorosilane generation step. Trichlorosilane first circulation step 103 that circulates in the silicon deposition step, and tetrachlorosilane reduction in which a part of tetrachlorosilane in the remaining components after trichlorosilane separation in the trichlorosilane first circulation step is reduced with hydrogen to obtain trichlorosilane Step 104, reduction of the tetrachlorosilane The tetrachlorosilane extraction step of taking out the remainder of the tetrachlorosilane supplied to the trichlorosilane second circulation step 105 and the tetrachlorosilane reduction step for circulating the gas after the reaction to the trichlorosilane generation step and supplying it to the tetrachlorosilane treatment facility A method of adjusting the extraction amount by changing the molar ratio of hydrogen to trichlorosilane supplied to the silicon deposition step can be adopted.
[0076]
In the silicon production method of the present invention, if the molar ratio of hydrogen to TCS is reduced, a large amount of STC can be generated, and if the molar ratio is increased, the STC can be decreased. Accordingly, the silicon may be deposited by controlling the molar ratio according to the amount of STC taken out by the STC extraction process and required by the STC processing equipment 203. Usually, the molar ratio of hydrogen to such TCS can be controlled in the range of 5-30.
[0077]
The STC processing facility includes all facilities that can effectively use STC. Typical equipment includes equipment for producing fumed silica by hydrolyzing the STC with an oxyhydrogen flame, an epitaxial equipment for silicon wafers, etc., and known equipment can be used without particular limitation. it can.
[0078]
【The invention's effect】
As can be understood from the above description, according to the method of the present invention, the amount of STC produced by the Siemens method is reached by performing the silicon precipitation reaction between TCS and hydrogen in a specific high temperature range. It can be suppressed to an extremely small amount that could not be considered, and the generated STC can be closed without taking it out of the process.
[0079]
In addition, by changing the ratio of hydrogen to TCS in the silicon precipitation reaction in the high temperature range, the amount of STC produced can be adjusted within a very wide range without affecting the quality of the silicon obtained. As a result, even when an STC processing facility is provided, the amount of STC supplied to the facility can be easily controlled, and an extremely balanced production mode can be adopted.
[0080]
【Example】
Hereinafter, examples will be given to describe the present invention more specifically, but the present invention is not limited to these examples.
[0081]
Example 1
According to the process shown in FIG. 4, silicon was manufactured as follows.
[0082]
In the deposition step 101, the apparatus shown in FIG. ² ), TCS and hydrogen were supplied so that the molar ratio of hydrogen to the TCS was the molar ratio shown in Table 1, and the inner wall of the cylindrical container 1 was heated to 1450 ° C. to generate silicon. At this time, the TCS is mixed with a part of hydrogen and supplied from the chlorosilanes supply pipe, and the remaining hydrogen gas is supplied as seal gas from the seal gas supply pipe 6 so that the total amount of hydrogen is as shown in Table 1. Supplied. A small amount of hydrogen was supplied from the seal gas supply pipe 11 as a seal gas. The reaction pressure was 50 kPaG.
[0083]
Table 1 shows the silicon deposition amount, STC production amount, and hydrogen chloride production amount in the silicon deposition step. Note that the STC generation amount and the hydrogen chloride generation amount at this time are calculated by analyzing the exhaust gas of the silicon precipitation reaction using a gas chromatograph.
[0084]
The gas after the reaction in the silicon deposition step was pressurized to about 700 kPaG with a pressurizer, heated, and supplied to the TCS generation step 102. In the TCS generation step, a fluidized bed reactor of metallurgical grade silicon as raw material silicon was used. The reaction conditions for the TCS generation step were a temperature of 350 ° C. and a pressure of 700 kPaG, and about 10 kg of raw material silicon was filled. The raw material silicon had an average particle size of about 200 μm and a purity of 98%, and contained carbon, phosphorus and boron in addition to metals such as iron, aluminum, titanium and calcium as main impurities.
[0085]
Further, dry hydrogen chloride gas was supplied to the TCS generation step 102. The supply amount of the hydrogen chloride gas was an amount for keeping the chlorine content in the system, and was the amount shown in Table 1. This amount balances the chlorine content in the chlorosilane discharged out of the system, such as the heavy end extracted in the distillation purification system, and in some cases STC extracted as a surplus.
[0086]
In the TCS generation step 102, hydrogen chloride generated in the silicon precipitation step 101 and the STC reduction step 104 described later, and in addition to this, hydrogen chloride supplied to maintain the amount held in the system reacts with the raw material silicon, A product TCS and a by-product STC are generated.
[0087]
The gas discharged from the TCS generation process 102 is supplied to the hydrogen / chlorosilane separation process 201 after removing fine silicon silicon powder accompanying the gas with a filter, and cooled to −30 ° C. to cool the gas to chlorosilane. A portion of the product was condensed to separate the hydrogen gas. The separated hydrogen gas was distributed and supplied to the silicon deposition step 101 and the STC reduction step 104 described later.
[0088]
Here, hydrogen gas obtained by separating a part of the chlorosilanes is converted to -N (CH ₃ ) ₂ When the sample was passed through a container filled with 10 liters of sufficiently dried ion exchange resin having a substituent of the following, the purity of the silicon precipitate was P-type 50 Ω · cm. Incidentally, the purity of the silicon precipitate when no ion exchange resin was used was P-type 1 Ω · cm.
[0089]
On the other hand, the condensed chlorosilanes were supplied to the distillation purification tower of the TCS first circulation step 103 and separated into heavy ends containing TCS, STC, and heavy metals.
[0090]
In addition, TCS and STC separated and purified in the TCS first circulation step 103 were vaporized, and TCS was supplied to the silicon deposition step, and STC was supplied to the STC reduction step so as to have the amounts shown in Tables 1 and 2. . In the STC reduction step 104, a reduction reaction was performed with the molar ratio of hydrogen set to 10 with respect to the STC. At this time, the supply amount of hydrogen is about 50 Nm because the total amount supplied to the silicon deposition step 101 and the STC reduction step 104 is limited by the limitation of the pressurizer. ³ / H was the upper limit. As the reactor for the STC reduction reaction, the same apparatus as the reactor shown in FIG. 1 was used, and a mixed gas of STC and hydrogen was supplied from the chlorosilane supply pipe 4. Other operating conditions were the same as those for the silicon precipitation reaction.
[0091]
Table 2 shows the reaction conditions for the STC reduction reaction and the amount of TCS produced by the reaction. The amount of TCS produced at this time is calculated by analyzing the exhaust gas of the STC reduction reaction using a gas chromatograph.
[0092]
The gas discharged from the STC reduction step was supplied to the TCS generation step 102 by the TCS second circulation step 105.
[0093]
Table 3 shows the amount of surplus STC, the amount of surplus STC per 1 kg of silicon production, the total hydrogen supply amount of precipitation reaction and STC reduction reaction, and silicon production for evaluating the effects and economics of the closed system described above. The hydrogen supply amount per kg of the amount is shown.
[0094]
Note that surplus STC means that even when the maximum amount of STC that can be supplied to the STC reduction reaction is supplied, STC is generated by the silicon precipitation reaction or the like, and therefore, as shown in FIG. STC that must be discharged out of the system.
[0095]
As described above, according to the present invention, it is possible to suppress the generation of STC in the silicon deposition step 101, and it is possible to provide a closed system that does not generate surplus STC even with a small-scale STC reduction reaction facility. It is understood that there is.
[0096]
Examples 2 and 3
In Example 1, silicon was manufactured by the same process except that the molar ratio of hydrogen to TCS in the silicon deposition process 101 was changed as shown in Table 1.
[0097]
The production amount of the product in each step is shown in Tables 1 to 3 with the same display as in Example 1.
[0098]
As with the first embodiment, it is understood that an economical closed system can be implemented.
[0099]
Example 4
In Example 1, as a result of changing the molar ratio of hydrogen to TCS to 5 in the silicon deposition step 101, as shown in Table 3, 15.6 kg / H of surplus STC could be generated. This was calculated to be a surplus STC amount of 14.9 kg per kg of silicon production, and an STC equivalent to the surplus STC amount of the Siemens method described later could be obtained.
[0100]
Examples 5 and 6
In Example 1, the deposition reaction temperature in the silicon deposition step 101 was changed to 1350 ° C., the molar ratio of hydrogen to TCS was changed as shown in Table 1, and the reduction reaction temperature in the STC reduction step 104 was also changed to 1350 as shown in Table 2. It carried out by changing to ℃. At this time, the inner wall temperature of the cylindrical container was raised to 1450 ° C. or more once per hour for about 5 minutes, and the reaction was continued while the precipitate was melted and dropped intermittently.
[0101]
As a result, as shown in Table 3, the closed system could be implemented in the same manner as in Example 1.
[0102]
As shown in Examples 1-6 above, according to the present invention, the deposition reaction temperature in the silicon deposition step 101 is made equal to or higher than 1300 ° C., and by changing the molar ratio of hydrogen to TCS. It is understood that a very wide range of operation is possible, from a complete closed system to a large amount of surplus STC acquisition, depending on the size of the equipment. That is, according to the present invention, it is possible to very flexibly cope with a change in the demand amount of the STC processing equipment without changing the equipment scale for generating silicon.
[0103]
Comparative Example 1
In the silicon deposition step 101 and the STC reduction step 104 of Example 1, a bell jar type reactor (deposition surface area of about 1200 cm) generally used in the Siemens method. ² )It was used. At this time, the precipitation reaction temperature and the reduction reaction temperature were set to 1150 ° C., which is an upper limit temperature industrially feasible in the conventional Siemens method, and the reaction pressure was set to 50 kPaG as in Example 1.
[0104]
In this case, in the silicon deposition step 101, the molar ratio of hydrogen to TCS is 10 because the industrial upper limit for maintaining a stable precipitation reaction by smoothing the shape of the silicon precipitate is about 10. did.
[0105]
The other processes were operated under the same conditions as in Example 1.
[0106]
[Table 1]

[Table 2]

[Table 3]

From the above comparative example, it is understood that a large amount of surplus STC is generated when silicon deposition is carried out at a temperature below the melting point, particularly by the conventional Siemens method.
[0107]
Further, as understood in comparison with Example 4, the production amount of silicon is about four times larger in Example 4 even in the same scale of equipment, and the method according to the present invention has extremely excellent economic efficiency. I understand that.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an apparatus for silicon deposition that is preferably used in the practice of the method of the present invention.
FIG. 2 is a schematic diagram of another apparatus for silicon deposition that is preferably used to carry out the method of the present invention.
FIG. 3 is a graph showing the tendency of the production amount of STC and hydrogen chloride at the precipitation temperature.
FIG. 4 is a process diagram showing a typical embodiment of the present invention.
FIG. 5 is a process diagram showing another representative embodiment of the present invention.
[Explanation of symbols]
1 cylindrical container
3 Heating device
4 Chlorosilane supply pipe
5 Seal gas supply pipe
6 Seal gas supply pipe
7 Sealed container
8 Silicon
9 Coolant
11 Seal gas supply pipe 11
12 Extraction piping
15 space
16 Heating means

Claims (5)

A silicon deposition step in which trichlorosilane and hydrogen are reacted at a temperature of 1300 ° C. or more to produce silicon; a gas after reaction in the silicon deposition step is brought into contact with the raw material silicon; and hydrogen chloride contained in the exhaust gas A trichlorosilane production step for producing trichlorosilane by reaction with silicon and a trichlorosilane first circulation step in which trichlorosilane is separated from the gas after the reaction in the trichlorosilane production step and circulated to the silicon deposition step. A method for producing silicon. 2. The method for producing silicon according to claim 1, wherein in the silicon deposition step, the molar ratio of hydrogen to trichlorosilane is 10 or more. A silicon deposition step in which trichlorosilane and hydrogen are reacted at a temperature in which the molar ratio of hydrogen to trichlorosilane is 10 or more and at a temperature of 1300 ° C. or more to produce silicon, and the gas after the reaction in the silicon deposition step is used as a raw material A trichlorosilane generation step in which trichlorosilane is produced by the reaction of hydrogen chloride and silicon contained in the exhaust gas in contact with silicon, trichlorosilane is separated from the gas after the reaction in the trichlorosilane generation step, and silicon precipitation In the trichlorosilane first circulation step that circulates in the process, the tetrachlorosilane reduction step in which the tetrachlorosilane in the remaining components after the trichlorosilane separation in the trichlorosilane first circulation step is reduced with hydrogen to obtain trichlorosilane, and the tetrachlorosilane reduction step Gas after reaction of Method for producing a silicon characterized by consisting of trichlorosilane second circulating step circulating in the trichlorosilane forming step. A silicon deposition step in which trichlorosilane and hydrogen are reacted at a temperature of 1300 ° C. or more to produce silicon; a gas after reaction in the silicon deposition step is brought into contact with the raw material silicon; and hydrogen chloride contained in the exhaust gas A trichlorosilane generation step for generating trichlorosilane by reaction with silicon, a trichlorosilane first circulation step in which trichlorosilane is separated from a gas after reaction in the trichlorosilane generation step and circulated to a silicon deposition step, a trichlorosilane first step A tetrachlorosilane reduction step for obtaining trichlorosilane by reducing a part of tetrachlorosilane in the remaining components after separation of trichlorosilane in the circulation step with hydrogen, and a gas after reaction in the tetrachlorosilane reduction step to the trichlorosilane generation step Circulating trichlorosila The remainder of the tetrachlorosilane supplied to the second circulation step and the tetrachlorosilane reduction step is taken out and the tetrachlorosilane extraction step to supply to the tetrachlorosilane treatment facility is included, and the molar ratio of trichlorosilane to hydrogen supplied to the silicon deposition step is A method for producing silicon, wherein the amount of extraction is adjusted by changing. The method for producing silicon according to claim 3 or 4, wherein a reaction temperature in the tetrachlorosilane reduction step is 1300 ° C or higher.

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