JP4780284B2 - Purification method of silane trichloride - Google Patents
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本発明は、半導体用多結晶シリコンを製造するための原料として用いられる三塩化シランの精製方法に関する。 The present invention relates to a method for purifying silane trichloride used as a raw material for producing polycrystalline silicon for semiconductors.
半導体デバイス用の多結晶シリコンは、シーメンス法に代表されるように、主に高温下でのクロルシランの水素還元あるいは熱分解によって製造されている。この半導体デバイス用多結晶シリコンは非常に高純度であることが要求されている。現状の製造工程での不純物の分離は、多結晶シリコン融液からの単結晶引き上げ、あるいは多結晶シリコンの原料であるクロロシランの精密蒸留によって行われている。しかし不純物の中でもホウ素はシリコンに近い分配係数を有するため、単結晶シリコンの引き上げでの除去は難しく、原料のクロロシランガスについて多段蒸留塔を用いた精密蒸留に依存している。 Polycrystalline silicon for semiconductor devices is produced mainly by hydrogen reduction or thermal decomposition of chlorosilane at high temperatures, as represented by the Siemens method. This polycrystalline silicon for semiconductor devices is required to have very high purity. The separation of impurities in the current manufacturing process is performed by pulling a single crystal from a polycrystalline silicon melt or by precision distillation of chlorosilane, which is a raw material for polycrystalline silicon. However, since boron has a distribution coefficient close to that of silicon among impurities, it is difficult to remove single crystal silicon by pulling up, and the raw material chlorosilane gas relies on precision distillation using a multistage distillation column.
従来、この多段蒸留塔を用いた精密蒸留において、ホウ素やアルミニウム等の不純物を分離する手段として、これらの高沸点錯体を形成させて分離する方法が数多く提案されている。例えば、(イ)少量の水や水蒸気を導入する方法（特許文献１、２）、（ロ）フェノール類、チッソ含有化合物などを導入する方法（特許文献３，４，５）、（ハ）シロキサン結合を有する化合物を導入する方法（特許文献６）などが知られている。
従来の上記(イ)の方法は、副生する塩酸によって蒸留装置が腐食し、その腐食によって蒸留装置の鋼から溶出したリン等による汚染の問題があり、上記(ロ)(ハ)の方法は有機物を含むため、かえってその有機物による汚染の問題がある。また、上記何れの方法においても高沸点錯体を形成するために過剰量を必要とし、そのため、それらの未反応物による汚染を招く問題がある。 In the conventional method (b), the distillation apparatus is corroded by hydrochloric acid produced as a by-product, and there is a problem of contamination due to phosphorus etc. eluted from the steel of the distillation apparatus due to the corrosion, and the methods (b) and (c) are Since it contains organic matter, there is a problem of contamination by the organic matter. Further, in any of the above methods, an excessive amount is required to form a high-boiling point complex, so that there is a problem of causing contamination by those unreacted substances.
具体的には、粗三塩化シランに含まれる不純物のホウ素は主に三塩化ホウ素（BCl3、沸点12.4℃）として存在し、これは二塩化シラン（沸点8℃）と沸点が近いため、多段蒸留塔において二塩化シランと共に三塩化シラン（沸点31.8℃）含みで分離されている。このホウ素を含む二塩化シランを主成分とする留出物は、半導体級二塩化シランを必要とする場合は、さらなる超精密蒸留にて精製しており、通常はこれを加水分解により二酸化珪素に変えることで無害化する。しかし、この方法ではシリコンおよび塩素の損失となるうえ、発火性の高い危険物である二塩化シランや三塩化シランを密閉系外で取り扱うことは、安全上の問題がある。また、加水分解によって副生する塩酸は装置の腐食を招き、またこれを廃棄するには環境汚染防止のため中和処理が必要である。また、二酸化珪素を分離回収する必要があり処理コストが嵩む問題がある。 Specifically, the impurity boron contained in the crude trichlorosilane is mainly present as boron trichloride (BCl 3 , boiling point 12.4 ° C), which is close to the boiling point of dichlorosilane (boiling point 8 ° C), so it is multistage. In the distillation column, it is separated together with silane dichloride and silane trichloride (boiling point 31.8 ° C.). This distillate containing silane dichloride containing boron as a main component is refined by further ultraprecision distillation when semiconducting grade silane dichloride is required, and this is usually converted into silicon dioxide by hydrolysis. Detoxify by changing. However, in this method, silicon and chlorine are lost, and handling of dichlorosilane and trichlorosilane, which are highly ignitable hazardous materials, outside the closed system has safety problems. In addition, hydrochloric acid produced as a by-product by hydrolysis causes corrosion of the apparatus, and in order to discard it, neutralization treatment is necessary to prevent environmental pollution. Further, there is a problem that it is necessary to separate and collect silicon dioxide, which increases processing costs.
本発明は、従来の精製方法における上記問題を解決したものであり、多結晶シリコンの原料となる三塩化シランについて、ホウ素等の不純物の分離効果に優れ、かつ不純物除去剤による汚染の問題を生じる虞もなく、精製効果に優れた精製方法を提供する。 The present invention solves the above-mentioned problems in the conventional purification method, and is excellent in the separation effect of impurities such as boron and has a problem of contamination by an impurity remover with respect to silane trichloride as a raw material for polycrystalline silicon There is no fear, and a purification method having an excellent purification effect is provided.
本発明によれば以下の精製方法が提供される。
〔１〕 金属シリコンに塩酸ガスを反応させて生成した三塩化シランを精製する工程において、該三塩化シランを含む混合流体を蒸留装置に導いて塩化シラン系ポリマーと接触させ、三塩化シランを蒸留させて精製する一方、上記混合流体に含まれる低沸点不純物を上記ポリマーに取り込ませて蒸留残として三塩化シランから分離し、上記ポリマーと共に系外に除去する精製方法であって、精製した三塩化シランガスを水素と共に赤熱したシリコン棒に接触させて水素還元または熱分解によって多結晶シリコンを析出させる反応炉の排出ガスから三塩化シランおよび四塩化珪素を蒸留分離して回収した、三塩化シランおよび四塩化珪素よりも高沸点の液体を上記塩化シラン系ポリマーとして用いることを特徴とする三塩化シランの精製方法。
〔２〕 上記[１]に記載する精製方法において、金属シリコンに塩酸ガスを反応させて生成した三塩化シランを含む混合ガスを凝縮して蒸留装置に導き、この蒸留装置で塩化シラン系ポリマーと接触させて三塩化シランを蒸留精製する一方、低沸点不純物を上記ポリマーに取り込ませて分離し、該蒸留装置を経由した三塩化シランをさらに精密蒸留装置に導いて三塩化シランを精密蒸留する三塩化シランの精製方法。
〔３〕 上記[１]または上記[２]に記載する精製方法において、三塩化シラン混合流体中の低沸点不純物が三塩化ホウ素を含むものであり、上記混合流体を塩化シラン系ポリマーに接触させて上記三塩化ホウ素を高沸点錯体に変性させ、これを上記ポリマーと共に系外に除去する三塩化シランの精製方法。
〔４〕 上記[１]〜上記[３]の何れかに記載する精製方法において、精製後の三塩化シランに含まれるホウ素濃度が１ppm以下である三塩化シランの精製方法。
According to the present invention, the following purification method is provided.
[1] In the process of purifying silane trichloride generated by reacting hydrochloric acid gas with metallic silicon, the mixed fluid containing the silane trichloride is introduced into a distillation apparatus and brought into contact with a silane chloride polymer to distill silane trichloride. A low boiling point impurity contained in the mixed fluid is incorporated into the polymer and separated from the silane trichloride as a distillation residue, and removed from the system together with the polymer. Silane trichloride and tetrachloride recovered by distilling and recovering silane trichloride and silicon tetrachloride from the exhaust gas of a reactor in which silane gas is brought into contact with a red hot silicon rod together with hydrogen to deposit polycrystalline silicon by hydrogen reduction or thermal decomposition. A method for purifying silane trichloride, wherein a liquid having a boiling point higher than that of silicon chloride is used as the chlorosilane-based polymer.
[2] In the purification method described in [1] above, a mixed gas containing trichlorosilane generated by reacting hydrochloric acid gas with metal silicon is condensed and led to a distillation apparatus. While contacting and purifying the silane trichloride by distillation, the low boiling point impurities are incorporated into the polymer and separated, and the silane trichloride that has passed through the distillation apparatus is further introduced into a precision distillation apparatus to perform precision distillation of the silane trichloride. Purification method of silane chloride.
[3] In the purification method described in [1] or [2] above, the low boiling point impurity in the silane trichloride mixed fluid contains boron trichloride, and the mixed fluid is brought into contact with the silane chloride polymer. A method for purifying silane trichloride, wherein the boron trichloride is modified into a high-boiling-point complex and removed from the system together with the polymer.
[4] The purification method according to any one of [1] to [3] above, wherein the boron concentration in the purified silane trichloride is 1 ppm or less.
〔具体的な説明〕
以下、本発明を具体的に説明する。なお、以下の説明において三塩化シランをＴＣＳと云い、四塩化ケイ素をＳＴＣと云う場合がある。
本発明の精製方法は、金属シリコンに塩酸ガスを反応させて生成した三塩化シランを精製する工程において、該三塩化シランを含む混合流体を蒸留装置に導いて塩化シラン系ポリマーと接触させ、三塩化シランを蒸留させて精製する一方、上記混合流体に含まれる低沸点不純物を上記ポリマーに取り込ませて蒸留残として三塩化シランから分離し、上記ポリマーと共に系外に除去する精製方法であって、精製した三塩化シランガスを水素と共に赤熱したシリコン棒に接触させて水素還元または熱分解によって多結晶シリコンを析出させる反応炉の排出ガスから三塩化シランおよび四塩化珪素を蒸留分離して回収した、三塩化シランおよび四塩化珪素よりも高沸点の液体を上記塩化シラン系ポリマーとして用いることを特徴とする三塩化シランの精製方法である。
[ Specific description ]
Hereinafter, the present invention will be specifically described. In the following description, silane trichloride may be referred to as TCS and silicon tetrachloride may be referred to as STC.
In the purification method of the present invention, in the step of purifying silane trichloride produced by reacting metal silicon with hydrochloric acid gas, the mixed fluid containing the silane trichloride is introduced into a distillation apparatus and brought into contact with the silane chloride polymer. While purifying by distilling silane chloride, the low boiling point impurities contained in the mixed fluid are taken into the polymer and separated from the trichloride silane as a distillation residue, and removed from the system together with the polymer, Silane trichloride and silicon tetrachloride were recovered by distillation separation from the exhaust gas from a reactor in which purified trisilane gas was brought into contact with a red-hot silicon rod together with hydrogen to deposit polycrystalline silicon by hydrogen reduction or thermal decomposition. trichlorosilane, which comprises using a high-boiling liquid than dichlorosilane and silicon tetrachloride as the chlorosilane-based polymer It is a purification method.
本発明は、多結晶シリコン生成反応において副生する塩化シラン系ポリマーを、三塩化シランを含有する塩化シラン混合流体に含まれる不純物を除去する除去剤として利用する。この塩化シラン系ポリマーとは、Ｓｉ−Ｓｉ結合あるいはＳｉ−Ｓｉ−Ｓｉ結合等のポリシラン結合を有するものを云う。なお、この塩化シラン系ポリマーをポリシランと云う場合がある。ポリシランは、例えば、精製した三塩化シランガスを水素と共に赤熱したシリコン棒に接触させて水素還元または熱分解によって多結晶シリコンを析出させる反応炉から排出された排液を用いることができる。 In the present invention, a silane chloride-based polymer by-produced in a polycrystalline silicon production reaction is used as a remover for removing impurities contained in a silane chloride mixed fluid containing silane trichloride. The chlorosilane-based polymer refers to a polymer having a polysilane bond such as a Si—Si bond or a Si—Si—Si bond. This chlorosilane-based polymer is sometimes referred to as polysilane. As the polysilane, for example, waste liquid discharged from a reaction furnace in which purified silicon silane gas is brought into contact with a red-hot silicon rod together with hydrogen to deposit polycrystalline silicon by hydrogen reduction or thermal decomposition can be used.
ポリシラン結合はシロキサン結合（Si-O−Si結合）よりも格段に配位能力が高く、二塩化シラン、三塩化シラン、四塩化珪素等のクロロシランにポリシランを添加すると、これらに含まれている三塩化ホウ素などのホウ素化合物と反応して容易に錯体を形成し、この錯体は三塩化シランよりも沸点がかなり高いので、三塩化シランから効果的に分離することができる。 Polysilane bonds have much higher coordination ability than siloxane bonds (Si-O-Si bonds), and when polysilane is added to chlorosilanes such as silane dichloride, silane trichloride, silicon tetrachloride, etc. It easily reacts with boron compounds such as boron chloride to form a complex, and this complex has a considerably higher boiling point than silane trichloride and can be effectively separated from silane trichloride.
具体的には、上記反応炉から排出された塩化シラン系ポリマー排液を蒸留装置に導入し、該蒸留装置において三塩化シランを含む塩化シラン混合ガスと混合して十分に気液接触させると、ホウ素が上記ポリマーに捕捉されて高沸点物を形成し、蒸留残となるので蒸留する塩化シランと分離することができる。具体的には、例えば蒸留前の三塩化シラン含有混合流体中のホウ素濃度が０.１％レベルであるものを、蒸留後には１ppm以下のレベルまで低減することができる。 Specifically, when the chlorosilane-based polymer drainage discharged from the reaction furnace is introduced into a distillation apparatus, and mixed with a silane chloride mixed gas containing trichlorosilane in the distillation apparatus and sufficiently brought into gas-liquid contact, Boron is trapped by the polymer to form a high-boiling product, which is a distillation residue and can be separated from the silane chloride to be distilled. Specifically, for example, the boron concentration in the silane trichloride-containing mixed fluid before distillation can be reduced to a level of 1 ppm or less after distillation when the boron concentration is 0.1%.
本発明の精製方法の一例を、図１の工程図に基づき、塩化反応装置における粗三塩化シランの生成、その精製工程、シリコン析出反応工程に従って具体的に説明する。図中、１０は三塩化シランを生成する塩化炉、１１は生成した塩化シラン混合ガスを凝縮する凝縮装置、１２は上記混合ガスに含まれる低沸点不純物を除去する蒸発装置、１４はこの粗三塩化シランを精製する精密蒸留装置、１６は多結晶シリコンの析出反応炉、１７は排ガスから水素を回収し精製する工程、１８は反応炉から排出された排出物から三塩化シランを分離回収する蒸留装置、１９は上記排出物から四塩化ケイ素を蒸発させて塩化シラン系ポリマーを分離する装置である。また、蒸発した粗三塩化シランを溜めるタンク（図示省略）、精密蒸留で得た半導体級純度の三塩化シランを溜めるタンク（図示省略）が設けられている。各装置は図示するように管路で連通されている。
An example of the purification method of the present invention will be specifically described according to the production of crude trichlorosilane in a chlorination reaction apparatus, its purification process, and silicon precipitation reaction process based on the process diagram of FIG. In the figure, 10 is a chlorination furnace for generating silane trichloride, 11 is a condenser for condensing the generated chlorosilane mixed gas, 12 is an evaporator for removing low-boiling impurities contained in the mixed gas, and 14 is this crude silane. Precision distillation apparatus for purifying silane chloride, 16 is a precipitation reaction furnace for polycrystalline silicon, 17 is a process for recovering and purifying hydrogen from exhaust gas, and 18 is a distillation for separating and recovering silane trichloride from the effluent discharged from the reactor. An apparatus 19 is an apparatus for separating the chlorosilane-based polymer by evaporating silicon tetrachloride from the effluent. There are also provided a tank (not shown) for storing the evaporated crude trichlorosilane and a tank (not shown) for storing semiconductor grade pure silane trichloride obtained by precision distillation. Each device is communicated with a pipe line as shown.
金属シリコン(純度９８wt％以上)、塩酸ガス、その他の工程で発生するシラン系ガス等を塩化反応装置(塩化炉１０)に投入し、金属シリコンの塩化反応によって、三塩化シランを主成分とする塩化シラン混合ガスを得る。この混合ガスに含まれる金属シリコンダストの大部分を除去した後に、この混合ガスを凝縮装置１１に導入して液化し、蒸発装置１２に導入する。 Metal silicon (purity 98 wt% or more), hydrochloric acid gas, silane-based gas generated in other processes, etc. are put into a chlorination reactor (chlorination furnace 10), and silane trichloride is the main component by chlorination reaction of metal silicon. A silane chloride mixed gas is obtained. After most of the metal silicon dust contained in the mixed gas is removed, the mixed gas is introduced into the condenser 11 to be liquefied and introduced into the evaporator 12.
蒸発装置１２には液化された上記混合流体が導入されると共にシリコン析出反応炉１６から排出された塩化シラン系ポリマーが導入され、この蒸発装置１２において粗塩化シランを含む上記混合流体と塩化シラン系ポリマーが混合され接触される。この蒸発装置１２は例えば、密閉攪拌槽に蒸発手段を設けた構造であり、槽内は三塩化シランの沸点以上に加熱され、蒸発した粗三塩化シランガスは冷却して液化し、タンク（図示省略）に導入され一時的に貯留される。
The liquefied mixed fluid is introduced into the evaporator 12 and the silane chloride polymer discharged from the silicon precipitation reactor 16 is introduced into the evaporator 12. In the evaporator 12, the mixed fluid containing the crude silane chloride and the silane chloride system are introduced. The polymer is mixed and contacted. The evaporator 12 is, for example, a structure in which a vaporization means in a closed stirring vessel, intracisternal is heated above the boiling point of trichlorosilane, vaporized crude three silane chloride liquefied by cooling, the tank (not shown ) And temporarily stored.
一方、蒸発装置１２において、上記混合流体に含まれている三塩化ホウ素などは塩化シラン系ポリマーに捕捉されて高沸点錯体を形成し、蒸発せずに残留する。これを上記ポリマーと共に系外に抜き出す。 On the other hand, in the evaporation apparatus 12, boron trichloride contained in the mixed fluid is trapped by the chlorosilane-based polymer to form a high boiling point complex, and remains without being evaporated. This is extracted out of the system together with the polymer.
タンク（図示省略）に一時的に貯留された粗三塩化シランは精密蒸留装置１４に導入される。精密蒸留装置１４は例えば蒸留塔を多段に設置した構造を有ししており、蒸留を繰り返すことによって、半導体級の超純度精製三塩化シランが得られる。この半導体級純度の三塩化シランは一時的にタンク（図示省略）に貯留された後に、多結晶シリコンの原料ガスとして反応炉１６に導入される。
The crude trichlorosilane temporarily stored in a tank (not shown) is introduced into the precision distillation apparatus 14. The precision distillation apparatus 14 has, for example, a structure in which distillation towers are installed in multiple stages, and semiconductor grade ultrapure purified silane trichloride can be obtained by repeating distillation. The semiconductor grade purity silane trichloride is temporarily stored in a tank (not shown) and then introduced into the reaction furnace 16 as a polycrystalline silicon source gas.
反応炉１６には原料の三塩化シランと共に水素が導入される。炉内には多結晶シリコンによって形成された多数のシリコン棒が立設しており、これに通電して炉内がおよそ８００〜１２００℃に加熱される。この赤熱したシリコン棒に三塩化シランガスと水素ガスが接触し、水素還元ないし熱分解によって多結晶シリコンがシリコン棒表面に析出し、次第にシリコン棒が成長する。一方、この析出反応の過程で、二塩化シランなどの低沸点シラン、四塩化珪素、塩化シラン系ポリマーが副生し、反応後に未反応の水素ガスや三塩化シランガスと共に反応炉１６から炉外に排出される。 Hydrogen is introduced into the reaction furnace 16 together with the raw material silane trichloride. A large number of silicon rods formed of polycrystalline silicon are erected in the furnace, and the interior of the furnace is heated to approximately 800 to 1200 ° C. by energizing the rod. Silane trichloride gas and hydrogen gas come into contact with the red-hot silicon rod, and polycrystalline silicon is deposited on the surface of the silicon rod by hydrogen reduction or thermal decomposition, and the silicon rod gradually grows. On the other hand, low boiling point silane such as silane dichloride, silicon tetrachloride, and silane chloride polymer are by-produced in the course of this precipitation reaction. Discharged.
この排出ガスは水素回収工程１７に導入され、ここで排出ガスに含まれる水素ガスが分離され、分離回収された水素は精製されて再び反応炉１６に導入される。
This exhaust gas is introduced into the
水素を分離した排出ガスは蒸留装置１８に導入され、ここで排出ガスに含まれている半導体級純度の三塩化シランが蒸留分離される。この回収した三塩化シランガスは、精密蒸留から導入された三塩化シランと共に一時的にタンク（図示省略）に貯留された後に、原料ガスとして再び反応炉１６に導入される。蒸留装置１８は通常の蒸留塔を用いることができる。
The exhaust gas from which the hydrogen has been separated is introduced into the distillation apparatus 18 where the semiconductor grade pure trichlorosilane contained in the exhaust gas is separated by distillation. The recovered silane trichloride gas is temporarily stored in a tank (not shown ) together with the silane trichloride introduced from the precision distillation, and then introduced again into the reaction furnace 16 as a raw material gas. The distillation apparatus 18 can use a normal distillation tower.
一方、塩化シラン系ポリマーと四塩化ケイ素を含む高沸点物は蒸留せずに残留する。この残留物を蒸留装置１８から抜き出して分離装置１９に導入する。 On the other hand, high-boiling substances containing a chlorosilane-based polymer and silicon tetrachloride remain without distillation. This residue is extracted from the distillation apparatus 18 and introduced into the separation apparatus 19.
分離装置１９において、塩化シラン系ポリマーは濃縮されて液状になり、この塩化シラン系ポリマー液が上記蒸発装置１２に導入され、先に述べたように粗塩化シランを含む混合流体と混合され、この混合流体に含まれている三塩化ホウ素がこの塩化シラン系ポリマーに捕捉されて高沸点錯体が形成され、粗三塩化シランから分離される。 In the separation device 19, the silane chloride polymer is concentrated to form a liquid, and this silane chloride polymer solution is introduced into the evaporation device 12 and mixed with the mixed fluid containing the crude silane chloride as described above. Boron trichloride contained in the mixed fluid is trapped by the chlorosilane-based polymer to form a high boiling point complex, which is separated from the crude silane trichloride.
本発明の精製方法によれば、塩化炉によって生成した粗三塩化シランガスに含まれるホウ素等の不純物を効率よく精製分離することができる。具体的には、三塩化シランガス中のホウ素濃度を１ppm以下、好ましくは０.０６ppbレベルに低減することができる。また、不純物除去剤であるポリシランとして、多結晶シリコン析出反応炉から排出されたポリマー液を用いることによって、塩化炉による三塩化シランの生成工程から、その精製工程、および多結晶シリコン析出工程に至る一連の製造工程において生じる副生物を他の工程において利用することができ、一連の製造工程の効率を高めることができる。 According to the purification method of the present invention, impurities such as boron contained in the crude trichlorosilane gas generated by the chlorination furnace can be efficiently purified and separated. Specifically, the boron concentration in the silane trichloride gas can be reduced to 1 ppm or less, preferably 0.06 ppb level. In addition, by using the polymer liquid discharged from the polycrystalline silicon deposition reactor as the polysilane which is an impurity removing agent, the production process from trichlorosilane to the purification process and the polycrystalline silicon deposition process from the chlorination furnace is achieved. By-products generated in a series of manufacturing processes can be used in other processes, and the efficiency of the series of manufacturing processes can be increased.
さらに、本発明の精製方法は、例えば多段蒸留精製工程において、任意の精製塔から抜き出した三塩化シランガスについて適用することができるので、精製条件に対応して容易に実施することができる。 Furthermore, since the purification method of the present invention can be applied to silane trichloride gas extracted from an arbitrary purification tower in, for example, a multistage distillation purification step, it can be easily carried out according to the purification conditions.
以下、本発明の実施例を示す。
〔実施例１〕
所定の温度範囲に制御された塩化反応装置により、二塩化シラン０.５wt％、三塩化シラン８８.０wt％、四塩化珪素１１.５wt％の平均組成からなる粗三塩化シランを得た。この粗三塩化シランに含まれるホウ素濃度は3,000〜6,000wtppbであった。
次に、この粗三塩化シラン１００重量部に対して、分離濃縮した塩化シラン系ポリマーを０.２重量部〜１.１重量部の範囲で蒸発装置に添加した。蒸発装置に添加した塩化シラン系ポリマーの平均組成は、四塩化珪素５４.３wt％、その他５.２wt％であり、Ｓｉ−Ｓｉ結合を有する塩化シラン系ポリマーの合計含有量は４０.５wt％であった。
この塩化シラン系ポリマーを粗三塩化シランに添加して蒸発処理したことによって、ホウ素系不純物がＳｉ−Ｓｉ結合を含むポリマーに捕捉されて高沸点錯体を形成し、これが系外へ排出された結果、精密蒸留装置へ導入される粗三塩化シラン中のホウ素濃度が２００ppba以下まで低減した。さらに、この粗三塩化シラン液を精密蒸留装置に導入して精製した三塩化シランは、ホウ素濃度が０.００５〜０.０１０ppbaであり、安定的に半導体級の三塩化シランを得ることができた。また、この半導体級三塩化シランを原料として得られた多結晶シリコン中のホウ素濃度も０.００５〜０.０１５ppbaで極めて安定した高純度多結晶シリコンを得ることができた。この結果を表１に示した。
Examples of the present invention will be described below.
[Example 1]
Crude trichloride silane having an average composition of 0.5 wt% silane dichloride, 88.0 wt% silane trichloride, and 11.5 wt% silicon tetrachloride was obtained by a chlorination reactor controlled in a predetermined temperature range. The boron concentration contained in this crude trichlorosilane was 3,000 to 6,000 wtppb.
Next, the separated and concentrated silane-based polymer was added to the evaporator in the range of 0.2 to 1.1 parts by weight with respect to 100 parts by weight of the crude trichlorosilane. The average composition of the silane chloride polymer added to the evaporator is 54.3 wt% silicon tetrachloride and 5.2 wt%, and the total content of the silane chloride polymers having Si-Si bonds is 40.5 wt%. there were.
As a result of adding this chlorosilane-based polymer to the crude trichlorosilane and evaporating it, boron-based impurities are trapped by the polymer containing Si-Si bonds to form a high-boiling-point complex, which is discharged out of the system. The boron concentration in the crude trichlorosilane introduced into the precision distillation apparatus was reduced to 200 ppba or less. Further, silane trichloride purified by introducing this crude trichlorosilane solution into a precision distillation apparatus has a boron concentration of 0.005 to 0.010 ppba and can stably obtain semiconductor grade silane trichloride. It was. In addition, the boron concentration in the polycrystalline silicon obtained using this semiconductor grade silane trichloride as a raw material was 0.005 to 0.015 ppba, and highly stable polycrystalline silicon could be obtained. The results are shown in Table 1.
〔比較例〕
一方、蒸発装置へ塩化シラン系ポリマーを添加しなかった以外は実施例と同様にして三塩化シランを精製したところ、蒸発装置を経た粗三塩化シラン中のホウ素濃度は蒸発装置導入前の粗三塩化シラン中のホウ素濃度とほほ同じ３０００〜６０００wtppbであった。この粗三塩化シラン液を精密蒸留装置に導入し、実施例と同じ蒸留条件によって三塩化シランを精製したところ、精製後の三塩化シラン中のホウ素濃度は０.０２５〜０.０５０ppbaであり、本発明の実施例の約５倍であった。また、この三塩化シランを原料として得られた多結晶シリコン中のホウ素濃度は０.０２５〜０.０６０ppbaであり、本発明の実施例の約５倍であった。この結果を表１に示した。
[Comparative Example]
On the other hand, when silane trichloride was purified in the same manner as in the Examples except that the silane chloride polymer was not added to the evaporator, the boron concentration in the crude silane trichloride that passed through the evaporator was the same as that of the crude It was 3000 to 6000 wtppb which was almost the same as the boron concentration in chlorosilane. When this crude trichlorosilane solution was introduced into a precision distillation apparatus and silane trichloride was purified under the same distillation conditions as in the examples, the boron concentration in the silane trichloride after purification was 0.025 to 0.050 ppba, It was about 5 times that of the embodiment of the present invention. The boron concentration in the polycrystalline silicon obtained using silane trichloride as a raw material was 0.025 to 0.060 ppba, which was about 5 times that of the example of the present invention. The results are shown in Table 1.
以上のように、本発明の精製方法は、Ｓｉ−Ｓｉ結合を含む塩化シラン系ポリマーを、粗三塩化シランに添加して蒸留処理を行うことによって、蒸留前の粗三塩化シランに含まれるホウ素濃度を従来の３０分の１以下に低減することができ、次工程の精密蒸留におけるホウ素系不純物除去の負荷を大幅に軽減することができた。また、精製された半導体級三塩化シランに含まれるホウ素濃度を安定して低く抑えることができ、その結果、極めて品質の安定した超高純度多結晶シリコンを生産することができた。 As described above, the purification method of the present invention adds boron chloride-containing polymer containing Si—Si bonds to crude trichloride silane and performs a distillation treatment to thereby obtain boron contained in the crude trichloride silane before distillation. The concentration could be reduced to 1/30 or less of the conventional one, and the load of removing boron impurities in the subsequent precision distillation could be greatly reduced. Further, the boron concentration contained in the purified semiconductor grade silane trichloride could be stably kept low, and as a result, ultra-high purity polycrystalline silicon with extremely stable quality could be produced.
１０−塩化炉、１１−凝縮装置、１２−蒸発装置、１４−精密蒸留装置、１６−反応炉、１７−水素回収精製工程、１８−蒸留装置、１９−塩化シラン系ポリマーの分離装置。
10-chlorination furnace, 11-condenser, 12-evaporator, 14-precision distillation apparatus, 16-reactor, 17-hydrogen recovery and purification step, 18-distillation apparatus, 19-silane chloride polymer separation apparatus.
Claims (4)
In the process of purifying silane trichloride generated by reacting hydrochloric acid gas with metallic silicon, the mixed fluid containing the silane trichloride is brought into contact with a silane chloride polymer through a distillation device and purified by distilling the silane trichloride. On the other hand, a low boiling point impurity contained in the mixed fluid is taken into the polymer and separated from the silane trichloride as a distillation residue and removed from the system together with the polymer, and the purified silane trichloride gas is hydrogenated. From silane trichloride and silicon tetrachloride recovered by distillation separation of silane trichloride and silicon tetrachloride from the exhaust gas of a reactor in which polycrystalline silicon is deposited by hydrogen reduction or thermal decomposition by contacting with a red hot silicon rod A method for purifying silane trichloride, wherein a high boiling point liquid is used as the silane chloride polymer.
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| CN101377376B (en) * | 2007-08-29 | 2012-06-06 | 中国恩菲工程技术有限公司 | Method for recovering tail gas generated by polycrystalline silicon production |
| DE102008002537A1 (en) * | 2008-06-19 | 2009-12-24 | Evonik Degussa Gmbh | Process for the removal of boron-containing impurities from halosilanes and plant for carrying out the process |
| JP5429464B2 (en) * | 2009-07-16 | 2014-02-26 | 三菱マテリアル株式会社 | Purification method of silane trichloride |
| WO2011024276A1 (en) | 2009-08-27 | 2011-03-03 | 電気化学工業株式会社 | Method for purifying chlorosilane |
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| US8226920B1 (en) * | 2011-01-07 | 2012-07-24 | Mitsubishi Polycrystalline Silicon America Corporation (MIPSA) | Apparatus and method for producing polycrystalline silicon having a reduced amount of boron compounds by venting the system with an inert gas |
| JP5742622B2 (en) * | 2011-09-20 | 2015-07-01 | 三菱マテリアル株式会社 | Trichlorosilane production method and production apparatus |
| DE102011089479A1 (en) * | 2011-12-21 | 2013-06-27 | Wacker Chemie Ag | Polycrystalline silicon |
| JP6287081B2 (en) * | 2013-11-06 | 2018-03-07 | 三菱マテリアル株式会社 | Tetrachlorosilane recovery method and polycrystalline silicon production method |
| CN104928761B (en) * | 2014-03-19 | 2018-02-23 | 新特能源股份有限公司 | A kind of preparation method of silicon chip foundry alloy |
| JP7313270B2 (en) | 2019-12-24 | 2023-07-24 | 高純度シリコン株式会社 | Method for purifying high-purity trichlorosilane |
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