JP4766882B2 - Silicon coagulation purification apparatus and coagulation purification method - Google Patents
Silicon coagulation purification apparatus and coagulation purification method Download PDFInfo
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本発明は、低純度シリコンを一方向に凝固させることにより、金属元素等を除去し、太陽電池原料等に用いられる高純度シリコンを製造するための、シリコンの凝固精製装置及び凝固精製方法に関するものである。 The present invention relates to a solidification purification apparatus and a solidification purification method for producing high purity silicon used for solar cell materials and the like by removing metal elements and the like by solidifying low purity silicon in one direction. It is.
太陽電池等に用いられる高純度Ｓｉ（シリコン）は、予めＳｉの融点以上に加熱された鋳型内に、溶融Ｓｉが別の容器から注湯されるか、又は、鋳型内で固体Ｓｉを溶解した後、鋳型底部に水冷プレート等を接触させ、徐々に抜熱することによって、溶融Ｓｉが下方から上方に向かって凝固することによって製造されるのが一般的である（例えば、特許文献１）。 High-purity Si (silicon) used in solar cells or the like is such that molten Si is poured from another container into a mold that has been heated to a melting point of Si or higher, or solid Si is dissolved in the mold. Thereafter, it is generally manufactured by bringing a water-cooled plate or the like into contact with the bottom of the mold and gradually removing heat to solidify the molten Si from below to above (for example, Patent Document 1).
溶融Ｓｉを一方向に凝固させると、不純物である金属元素が上部に偏析することにより、Ｓｉが高純度化されるが、偏析の仕方は、凝固速度、即ち、鋳型底部からの抜熱速度に大きく依存する。このため、近年、Ｓｉの凝固が進む間に鋳型底部と水冷プレートとの間に挟む断熱材の熱伝導率を変化させる方法（特許文献２）や、鋳型底部から熱を奪う冷媒の温度変化を検知して、鋳型からの抜熱量を測定、予め求めた凝固速度と抜熱量の関係から、この抜熱量を変化させることにより凝固速度を一定にする方法（特許文献３）等が試みられている。 When molten Si is solidified in one direction, the metal element as an impurity is segregated in the upper part, so that Si is highly purified. The segregation method depends on the solidification rate, that is, the heat removal rate from the mold bottom. It depends heavily. For this reason, in recent years, the method of changing the thermal conductivity of the heat insulating material sandwiched between the mold bottom and the water-cooled plate while the solidification of Si proceeds (Patent Document 2), or the temperature change of the refrigerant that takes heat away from the mold bottom. Detecting and measuring the amount of heat removed from the mold, and a method of making the solidification rate constant by changing the amount of heat removed from the relationship between the solidification rate and the amount of heat removal obtained in advance (Patent Document 3), etc. .
前述のＳｉ製造は、基本的に加熱されたＳｉが酸化されない、密閉可能な容器内で、真空中あるいは不活性ガス雰囲気下で行われる。そのため、加熱手段としてＣヒータあるいは電子銃（例えば、特許文献４）が用いられ、鋳型や断熱材もＣ系の材料で構成されている。
低純度ＳｉからＢやＰ等の軽元素を除去するだけでは、太陽電池用原料としての純度は不十分で、次に、溶融Ｓｉを一方向に凝固させることにより、金属不純物元素を除去する工程が必要である。この工程では通常、加熱ヒータ、鋳型、及び断熱材にＣ系材料が使用されているため、密閉可能な容器内で、真空中あるいは不活性ガス雰囲気下で行われる。もし、酸素ガスが混入する雰囲気で操業を行った場合、高価なＣ系の材料の酸化損耗が激しいため、コスト高となってしまう。 By simply removing light elements such as B and P from low-purity Si, the purity as a raw material for solar cells is insufficient. Next, the process of removing metal impurity elements by solidifying molten Si in one direction is required. In this step, since a C-based material is usually used for the heater, the mold, and the heat insulating material, the process is performed in a vacuum or in an inert gas atmosphere in a sealable container. If the operation is performed in an atmosphere in which oxygen gas is mixed, the cost of the expensive C-based material is high because of the oxidative wear of the expensive C-based material.
前記軽元素の除去が非密閉装置内で行われ、続けて一方向凝固によりＳｉを精製する場合、溶融Ｓｉの凝固装置内の鋳型への移送が必要となるが、この溶融Ｓｉの流通経路及び凝固装置全体を密閉化することは容易でなく、また、実現可能であっても、高価なものとなってしまう。したがって、凝固装置内の鋳型に溶融Ｓｉが移送される際には、大気中の酸素ガスの混入は避けられない。 When the removal of the light element is performed in an unsealed device and Si is subsequently purified by unidirectional solidification, it is necessary to transfer the molten Si to the mold in the solidification device. It is not easy to seal the entire coagulation apparatus, and even if it can be realized, it becomes expensive. Therefore, when molten Si is transferred to the mold in the solidification apparatus, it is inevitable that oxygen gas in the atmosphere is mixed.
本発明は、上記の事情を鑑み、酸素ガスが混入する雰囲気においても、溶融Ｓｉを多量に酸化させることなく、一方向に凝固させることが可能で、密閉容器及び真空ポンプを必要としない安価なＳｉの凝固精製装置及び凝固精製方法を提供することを目的としている。 In view of the above circumstances, the present invention can be solidified in one direction without oxidizing a large amount of molten Si even in an atmosphere mixed with oxygen gas, and does not require a sealed container and a vacuum pump. It aims at providing the coagulation refinement | purification apparatus and the coagulation purification method of Si.
本発明者らは、上記課題解決のため鋭意研究を行った結果、以下の手段により目的を達成するに到った。 As a result of intensive studies for solving the above problems, the present inventors have achieved the object by the following means.
第１の発明は、非密閉炉体と、その中に設置された、溶融Ｓｉを凝固させるための鋳型と、鋳型及び鋳型内の溶融Ｓｉの上方を加熱するための加熱手段と、鋳型底部を冷却するための冷却手段と、炉体内を断熱する断熱手段と、不活性ガスの導入手段と、を少なくとも備えたＳｉ凝固精製装置であって、前記加熱手段がＳｉＣを主成分とするヒータであり、前記断熱手段がＡｌ２Ｏ３を主成分とする断熱材であり、前記鋳型の材質の主成分がＳｉＣ又はＡｌ ２ Ｏ ３ であることを特徴とするＳｉ凝固精製装置である。 According to a first aspect of the present invention, there is provided a non-sealed furnace body, a mold for solidifying molten Si, heating means for heating the mold and the upper portion of the molten Si in the mold, and a mold bottom portion. A Si solidification purification apparatus comprising at least a cooling means for cooling, a heat insulating means for insulating the furnace body, and an inert gas introducing means, wherein the heating means is a heater mainly composed of SiC. the thermal insulator der heat insulating means is mainly composed of Al 2 O 3 is, the main component of the material of the mold is Si coagulation purification device according to claim SiC or Al 2 O 3 der Rukoto.
第２の発明は、第１の発明において、前記鋳型の溶融Ｓｉと接触する部分にＳｉＯ２を主成分とした層を有するＳｉ凝固精製装置である。 The second invention is a Si coagulation purification device having a layer mainly composed of SiO 2 Oite to the first invention, the portion in contact with molten Si of the mold.
第３の発明は、第１の発明又は第２の発明において、前記鋳型に炉体外から溶融Ｓｉを注ぐための手段を有するＳｉ凝固精製装置である。 A third invention is the Si solidification purification apparatus according to the first invention or the second invention, comprising means for pouring molten Si into the mold from outside the furnace body.
第４の発明は、第１〜第３のいずれかの発明に記載のＳｉ凝固精製装置を用いて、不活性ガスを導入し、炉体内に混入する酸素ガス濃度が、炉体容積当り、単位時間当り０．４ｍｏｌ／ｍ３・ｍｉｎ以下になるようにするＳｉ凝固精製方法である。 4th invention introduce | transduces an inert gas using the Si solidification refinement | purification apparatus as described in any one of 1st- 3rd invention, and the oxygen gas concentration mixed in a furnace body is a unit per furnace body volume. This is a Si solidification purification method in which the amount is 0.4 mol / m 3 · min or less per hour.
第５の発明は、第４の発明において、前記炉体内に設置された鋳型に大気中に曝された溶融Ｓｉを注ぐＳｉ凝固精製方法である。 The fifth invention is the Si solidification purification method according to the fourth invention, in which molten Si exposed to the atmosphere is poured into a mold installed in the furnace body.
本発明の溶融Ｓｉを一方向に凝固させて精製する装置及び方法によれば、装置内に酸素が混入する雰囲気においても、あるいは、別の精製工程を経て溶融Ｓｉを鋳型内に、大気中に曝された環境で移送する場合においても、酸化による歩留まり低下を抑制して、低コストで精製した高純度Ｓｉを提供することができる。 According to the apparatus and method for solidifying and purifying the molten Si of the present invention in one direction, even in an atmosphere in which oxygen is mixed in the apparatus, or through another purification process, the molten Si is put into the mold and into the atmosphere. Even when transporting in an exposed environment, it is possible to provide high-purity Si purified at a low cost by suppressing yield reduction due to oxidation.
本発明のＳｉ（シリコン）の凝固精製装置は、非密閉炉体と、その中に設置された、溶融Ｓｉを凝固させるための鋳型と、鋳型及び鋳型内の溶融Ｓｉの上方を加熱するためのＳｉＣ（炭化珪素）を主成分とするヒータ（加熱手段）と、鋳型底部を冷却するための冷却手段と、炉体内を断熱するためのＡｌ２Ｏ３（酸化アルミニウム）を主成分とする断熱材（断熱手段）と、不活性ガスの導入手段で、少なくとも構成される。 An apparatus for solidifying and purifying Si (silicon) according to the present invention includes a non-sealed furnace body, a mold installed therein for solidifying molten Si, and heating the mold and above the molten Si in the mold. A heater (heating means) mainly composed of SiC (silicon carbide), a cooling means for cooling the bottom of the mold, and a heat insulating material mainly composed of Al 2 O 3 (aluminum oxide) for thermally insulating the furnace body. (Insulation means) and inert gas introduction means.
ＳｉＣは、Ｃ（炭素）と比較して酸化性雰囲気に強く、表面に薄いＳｉＯ２（酸化シリコン）皮膜が形成されて保護層として働くため、また、Ａｌ２Ｏ３は、元々大気中でも安定な酸化物であるため、両者とも酸化性雰囲気での消耗は無く、工業的に量産されているので安価に入手し易い。ＳｉＣを主成分とするヒータは、酸化ホウ素を含んでいない珪酸等のバインダーを用いて、好ましくは、純度９０％以上のＳｉＣ粉を燒結したもの、また、Ａｌ２Ｏ３を主成分とする断熱材は、好ましくは、Ａｌ２Ｏ３の成分８０％以上、望ましくは９０％以上で、酸化ホウ素を含んでいない煉瓦、繊維、又は繊維を固めたボード等であれば、鋳型内の溶融ＳｉをＢ（ホウ素）等で汚染することは無い。 SiC is stronger in an oxidizing atmosphere than C (carbon), and a thin SiO 2 (silicon oxide) film is formed on the surface to serve as a protective layer. Al 2 O 3 is originally stable in the air. Since both are oxides, they are not consumed in an oxidizing atmosphere and are easily mass-produced industrially, so that they are easily available at low cost. The heater containing SiC as a main component is preferably formed by sintering SiC powder having a purity of 90% or more using a binder such as silicic acid not containing boron oxide, and heat insulation mainly containing Al 2 O 3. The material is preferably 80% or more of Al 2 O 3 component, desirably 90% or more, and is a brick, fiber, or a board in which the fiber is hardened, and the molten Si in the mold is used. There is no contamination with B (boron) or the like.
鋳型は、ＳｉＣ系、Ａｌ２Ｏ３系の材料で構成されることが好ましい。ＳｉＣ系の材料の場合、上記のヒータと同様の製法で、板状又は容器にしたもの、あるいは、好ましくは、純度９０％以上のＳｉＣ粉と酸化ホウ素を含んでいないバインダーを水等の液体で溶いた後、型枠に流し込んで、乾燥し、板状又は容器にしたもの等を用いる。この際、骨材として、Ａｌ２Ｏ３粒を混ぜても良い。Ａｌ２Ｏ３系の材料の場合、上記煉瓦を用いるか、又は、Ａｌ２Ｏ３粉と酸化ホウ素を含んでいないバインダーを水等の液体で溶いた後、型枠に流し込んで乾燥し、板状又は容器にしたもの等を用いる。板状にする場合、１枚は底部板、４枚は測部板として、箱型に組み合わせ可能で、分割も可能な組立鋳型として構成される。鋳型は、枠材で固定するか、各板が接触する部分に切り込み等を入れて保型する。また、鋳型の側面周囲に上記断熱材を充填するか、Ａｌ２Ｏ３、ＳｉＯ２粒を充填して、側部板が倒れないようにしても良い。一方、容器にする場合は、一体型の円筒状鋳型又は箱型鋳型として使用可能な形状のものを作製する。 The mold is preferably made of a SiC-based or Al 2 O 3 -based material. In the case of a SiC-based material, a plate or container made by the same manufacturing method as the heater described above, or preferably a binder containing no SiC powder with a purity of 90% or more and boron oxide is a liquid such as water. After melting, it is poured into a mold and dried to use a plate or container. At this time, Al 2 O 3 grains may be mixed as an aggregate. In the case of an Al 2 O 3 based material, the above brick is used, or a binder containing no Al 2 O 3 powder and boron oxide is dissolved in a liquid such as water, and then poured into a mold and dried. Use the shape or container. In the case of a plate shape, one is a bottom plate and four are measuring plates, which are configured as an assembly mold that can be combined in a box shape and can be divided. The mold is fixed with a frame material, or the mold is held by making a cut or the like in a portion where each plate contacts. Also, the side plate may be prevented from falling down by filling the heat insulating material around the side surface of the mold or by filling Al 2 O 3 or SiO 2 grains. On the other hand, when making into a container, the thing of the shape which can be used as an integral cylindrical mold or a box mold is produced.
上記鋳型を用いた場合、直接、溶融Ｓｉが接触すると、鋳型からの汚染を受ける可能性がある。特に、Ａｌ２Ｏ３系の材料では、溶融Ｓｉ内にＡｌが溶け込むことになってしまう。そこで、各鋳型材料の溶融Ｓｉが接触する部分全体に、ＳｉＯ２粉、又は、これに一部Ｓｉ３Ｎ４（窒化珪素）、ＳｉＣ粉を混ぜたものに、珪酸又は樹脂等を添加し、塗布した後、乾燥させた層（ＳｉＯ２を主成分とした層）を形成させることが望ましい。このことにより、鋳型からの汚染を抑制すると共に、凝固したＳｉの鋳型からの離型材としての役割を果たし、鋳型の繰り返し使用が可能となる。 When the above mold is used, there is a possibility of contamination from the mold when the molten Si is in direct contact. In particular, in the case of an Al 2 O 3 based material, Al is dissolved in molten Si. Therefore, silicic acid or a resin or the like is added to the entire portion of each mold material in contact with the molten Si in a mixture of SiO 2 powder, or a part of this mixed with Si 3 N 4 (silicon nitride), SiC powder, After application, it is desirable to form a dried layer (a layer containing SiO 2 as a main component). As a result, the contamination from the mold is suppressed, and it serves as a mold release material from the solidified Si mold, and the mold can be used repeatedly.
Ｓｉは酸化され易い材料のため、特に、溶融Ｓｉを酸化性雰囲気に曝しておくと、すぐに表面から酸化が進み、多くがＳｉＯ２化してしまい、歩留まりが低下することになるが、本発明者らは、装置内に混入する酸素ガスの許容量を見出した。これは、酸素ガスの混入が許容量以下であれば、初期には表面が酸化されるが、この酸化皮膜が酸化に対してバリア層として働くため、酸化層の成長速度を低くすることができるためである。Ｓｉ全体に対する酸化ロスの割合は、溶融Ｓｉの体積に対する表面積の割合にも拠るが、酸化ロス量は、溶融Ｓｉの表面積１ｍ２当たり０．５ｋｇ以下に抑えることが可能である。Ｓｉの酸化量は、炉体容積当たり、単位時間内に入り込む酸素ガス量に依存するため、溶融Ｓｉを１５５０℃で４時間保持した場合の酸素ガス量に対するＳｉの酸化量を調査した結果（図１）、酸素ガス量が０．４ｍｏｌ／ｍ３・ｍｉｎ（モル／ｍ３・分）以下であれば、酸化量が少ないことが確認できた。炉体内に前記酸素ガス量（０．４ｍｏｌ／ｍ３・ｍｉｎ）が混入した場合の酸化量の時間依存性も調査したところ（図２）、ある一定の酸化層厚みに達した後は、酸化速度が低下していくことも判った。 Since Si is a material that is easily oxidized, in particular, when molten Si is exposed to an oxidizing atmosphere, oxidation immediately proceeds from the surface, and most of it is converted to SiO 2 , resulting in a decrease in yield. They found an allowable amount of oxygen gas mixed in the apparatus. This is because the surface is oxidized in the initial stage if the oxygen gas is not allowed to be mixed, but this oxide film acts as a barrier layer against the oxidation, so that the growth rate of the oxide layer can be lowered. Because. Although the ratio of oxidation loss to the entire Si depends on the ratio of surface area to the volume of molten Si, the amount of oxidation loss can be suppressed to 0.5 kg or less per 1 m 2 of surface area of molten Si. Since the amount of oxidation of Si depends on the amount of oxygen gas entering the unit time per furnace volume, the result of investigating the amount of oxidation of Si with respect to the amount of oxygen gas when molten Si is held at 1550 ° C. for 4 hours (FIG. 1) When the amount of oxygen gas was 0.4 mol / m 3 · min (mol / m 3 · min) or less, it was confirmed that the amount of oxidation was small. When the time dependence of the oxidation amount when the oxygen gas amount (0.4 mol / m 3 · min) was mixed in the furnace was also investigated (FIG. 2), after reaching a certain oxide layer thickness, oxidation was performed. It was also found that the speed decreased.
炉体が、真空にするためのパッキン類を使用しない非密閉容器であっても、Ａｒ（アルゴン）等の不活性ガスを導入して、炉体内を陽圧にすることによって、炉体内に混入する酸素ガス量を、前記酸素ガス量以下に抑えることは可能である。不活性ガスは、炉体内で加熱されると上方に流れるため、又、なるべく層流にして炉体外からの酸素ガスの巻き込みを防ぐため、少なくとも２箇所以上、炉体下方から導入することが望ましい。炉体が非密閉容器であるため、不活性ガスの排出管は特に設ける必要はない。炉体全体を別の容器で覆い二重構造とし、炉体内及び前記容器と炉体間の空間両方に、不活性ガスを導入するか、あるいは、溶融Ｓｉの酸化を抑制するために、溶融Ｓｉ表面付近に不活性ガスを吹き込んでも良い。 Even if the furnace body is a non-sealed container that does not use packings to make a vacuum, it is mixed into the furnace body by introducing an inert gas such as Ar (argon) and making the furnace body positive pressure It is possible to suppress the amount of oxygen gas to be reduced below the amount of oxygen gas. Since the inert gas flows upward when heated in the furnace body, it is desirable to introduce at least two or more places from the lower part of the furnace body in order to prevent entrainment of oxygen gas from outside the furnace body as much as possible. . Since the furnace body is a non-hermetic container, it is not necessary to provide an inert gas discharge pipe. The entire furnace body is covered with another container to form a double structure, and an inert gas is introduced into both the furnace body and the space between the container and the furnace body, or in order to suppress oxidation of the molten Si, molten Si An inert gas may be blown in the vicinity of the surface.
別の容器内で、低純度Ｓｉを溶解したもの、又は、軽元素の除去等を終えた溶融Ｓｉを、炉体内の鋳型に移送する場合、前記容器を傾動させて、大気中に曝された溶融Ｓｉを注ぎ入れるため、炉体上方に漏斗等を設置した方が良い。漏斗は、ＳｉＯ２、ＳｉＣ、又はＡｌ２Ｏ３系材料が望ましいが、ＭｇＯ（酸化マグネシウム）やＣａＯ（酸化カルシウム）系材料でも、溶融Ｓｉとの接触時間が短く、材質自体の溶融Ｓｉへの混入も無視できるため、使用することが可能である。また、炉体上方にノズル付きのタンディッシュを設ける方法もあり、この場合、前記容器から、溶融Ｓｉがタンディッシュに傾注され、タンディッシュ上を流れる溶融Ｓｉは、ノズルより炉体内に落下し、鋳型に注ぎ込まれることになる。ノズル及びタンディッシュの溶融Ｓｉと接触する部分は、ＳｉＯ２、ＳｉＣ、Ａｌ２Ｏ３、ＭｇＯ、ＣａＯ系材料のいずれかであることが必要である。 In another container, when melted low-purity Si or melted Si after removal of light elements is transferred to a mold in the furnace, the container is tilted and exposed to the atmosphere. In order to pour molten Si, it is better to install a funnel or the like above the furnace body. The funnel is preferably made of SiO 2 , SiC, or Al 2 O 3 based material, but even MgO (magnesium oxide) or CaO (calcium oxide) based material has a short contact time with molten Si, and the material itself can be converted into molten Si. Mixing is negligible and can be used. There is also a method of providing a tundish with a nozzle above the furnace body, in this case, molten Si is poured from the container into the tundish, and the molten Si flowing over the tundish falls into the furnace body from the nozzle, It will be poured into the mold. The portion of the nozzle and tundish that contacts with the molten Si needs to be any of SiO 2 , SiC, Al 2 O 3 , MgO, and CaO-based materials.
図３は、本発明を実施するための装置の一例である。ステンレス製の非密閉炉体１の内面にＡｌ２Ｏ３系材料により、炉体１内を断熱する断熱材（断熱手段）である第１の断熱層３が形成され、その内側の下方に、組立型又は一体型のＳｉＣ又はＡｌ２Ｏ３系材料製の鋳型４が、その内面全体にＳｉＯ２を主成分とした離型層５が塗布された状態で設置される。鋳型４と第１の断熱層３の間の第２の断熱層７はＡｌ２Ｏ３系材料でなく、珪砂を充填しても良い。鋳型４内に低純度の固体Ｓｉ（固定シリコン）６が装入され、その上方には、ＳｉＣ系ヒータ（加熱手段）２が配置される。ＳｉＣ系ヒータ２は、通常、棒状のため、効率的に溶融Ｓｉを加熱できるように、ヒータ２を数本ずつ複数段にして、上から見ると碁盤の目のようになるように組み上げることが好ましい。 FIG. 3 is an example of an apparatus for carrying out the present invention. A first heat insulating layer 3 that is a heat insulating material (heat insulating means) for heat insulating the inside of the furnace body 1 is formed on the inner surface of the stainless steel non-sealed furnace body 1 with an Al 2 O 3 based material, An assembly-type or integral-type mold 4 made of SiC or Al 2 O 3 -based material is installed in a state where a release layer 5 mainly composed of SiO 2 is applied to the entire inner surface. The second insulation layer 7 between the mold 4 and the first heat insulating layer 3 is not Al 2 O 3 based material, it may be filled with quartz sand. A low-purity solid Si (fixed silicon) 6 is charged into the mold 4, and an SiC-based heater (heating means) 2 is disposed above it. Since the SiC-based heater 2 is usually rod-shaped, it can be assembled in several stages so that the molten Si can be efficiently heated so that it looks like a grid when viewed from above. preferable.
不活性ガスの導入手段であるＡｒガス導入管１０から装置内にＡｒガスを導入しながら、ヒータ２により鋳型４及び固体Ｓｉ６の加熱を始める。Ｓｉを凝固させる際には、鋳型４の底面からの抜熱を積極的に行うため、ステンレス又はＣｕ製水冷板（冷却手段）９を鋳型底面に接触させるが、固体Ｓｉ６が溶解し、その後、凝固を開始する前までは、鋳型４の底面と水冷板（冷却手段）９の間に断熱材８を挟み、効率的に鋳型４及び固体Ｓｉ６を加熱できるようにする。Ａｒガス導入管１０の位置や、本数、及びＡｒガスの流量は、装置内への酸素ガスの混入が上記許容量以下になるように決定する。 The heating of the mold 4 and the solid Si 6 is started by the heater 2 while introducing Ar gas into the apparatus from the Ar gas introduction pipe 10 which is an inert gas introduction means. When solidifying Si, in order to positively remove heat from the bottom surface of the mold 4, a water-cooled plate (cooling means) 9 made of stainless steel or Cu is brought into contact with the bottom surface of the mold, but the solid Si 6 is dissolved, Before the solidification is started, the heat insulating material 8 is sandwiched between the bottom surface of the mold 4 and the water cooling plate (cooling means) 9 so that the mold 4 and the solid Si 6 can be efficiently heated. The position and number of Ar gas introduction pipes 10 and the flow rate of Ar gas are determined so that the oxygen gas mixed into the apparatus is less than the allowable amount.
ヒータ２により溶解したＳｉを融点以上の温度、好ましくは１４２０〜１６００℃で、１０〜６０分の間、鋳型４内で保持する。１６００℃超に昇温すると、ヒータ２、鋳型４、第１の断熱層３等に過度に負荷がかかり、寿命を縮めることになってしまう。温度が均一になったところで、断熱材８を抜き取り、水冷板９を鋳型４の底面に接触させる。溶融Ｓｉの高さ方向の凝固速度が０．０５〜１ｍｍ／ｍｉｎ（ｍｍ／分）になるように、ヒータ２に印加する電力を制御する。０．０５ｍｍ／ｍｉｎ未満の速度では生産性が低過ぎ、１ｍｍ／ｍｉｎ超の速度だと精製が困難になってしまう。 Si melt | dissolved by the heater 2 is hold | maintained in the casting_mold | template 4 for 10 to 60 minutes at the temperature more than melting | fusing point, Preferably it is 1420-1600 degreeC. When the temperature is raised to over 1600 ° C., the heater 2, the mold 4, the first heat insulating layer 3 and the like are excessively loaded and the life is shortened. When the temperature becomes uniform, the heat insulating material 8 is extracted, and the water-cooled plate 9 is brought into contact with the bottom surface of the mold 4. The electric power applied to the heater 2 is controlled so that the solidification rate of the molten Si in the height direction is 0.05 to 1 mm / min (mm / min). If the speed is less than 0.05 mm / min, the productivity is too low, and if it exceeds 1 mm / min, purification becomes difficult.
図４は、低純度Ｓｉを溶解したもの又は軽元素の除去等を終えた溶融Ｓｉ（溶融シリコン）１２を鋳型４内に注いだ後、一方向に凝固させるための装置の一例である。炉体上方から大気中に曝された溶融Ｓｉ１２を鋳型内に注湯するための漏斗１３が挿入されている。 FIG. 4 shows an example of an apparatus for solidifying in one direction after pouring molten Si (molten silicon) 12 in which low-purity Si is dissolved or light elements are removed from the mold 4. A funnel 13 for pouring molten Si12 exposed to the atmosphere from above the furnace body into the mold is inserted.
最初に、漏斗１３の部分から空気が入らないように蓋をして、Ａｒガス導入管１０から装置内にＡｒガスを導入しながら、ヒータ２により鋳型４の加熱を始める。このとき、鋳型４の底面と水冷板９の間に断熱材８を挟み、効率的に鋳型及び溶融Ｓｉを加熱できるようにする。容器１１内で溶解された低純度Ｓｉ又は軽元素の除去を終えた溶融Ｓｉは、１４２０〜１６００℃に昇温された鋳型４に注湯される。１０〜６０分間保持し、溶融Ｓｉの温度が均一になったところで、ステンレス又はＣｕ製水冷板９を鋳型底面に接触させて、前記凝固速度で凝固を開始する。 First, a lid is applied so that air does not enter from the funnel 13, and heating of the mold 4 is started by the heater 2 while introducing Ar gas into the apparatus from the Ar gas introduction pipe 10. At this time, the heat insulating material 8 is sandwiched between the bottom surface of the mold 4 and the water cooling plate 9 so that the mold and the molten Si can be efficiently heated. The low purity Si dissolved in the container 11 or the molten Si after the removal of the light elements is poured into the mold 4 heated to 1420 to 1600 ° C. When the temperature of the molten Si becomes uniform for 10 to 60 minutes, the water-cooled plate 9 made of stainless steel or Cu is brought into contact with the bottom of the mold, and solidification is started at the solidification rate.
（実施例１）
図３に示した装置において、一辺が１．２ｍステンレス製炉体１の内面に厚さ１００ｍｍのＡｌ２Ｏ３製断熱層３が充填され、その内側上方に、直径２０ｍｍで、発熱体の部分が７００ｍｍのＳｉＣヒータ２を６本ずつ、直交するように２段に配置した。
Example 1
In the apparatus shown in FIG. 3, the inner side of a 1.2 m stainless steel furnace body 1 is filled with a heat insulating layer 3 made of Al 2 O 3 having a thickness of 100 mm. Six 700 mm SiC heaters 2 were arranged in two stages so as to be orthogonal to each other.
鋳型４は、内側に一辺が５００ｍｍで高さ４００ｍｍの空間が確保できるように、厚さ１５ｍｍのＳｉＣ板を組んで、さらに、内面に厚さ３ｍｍのＳｉＯ２層（離型層５）を塗布した。尚、鋳型４と断熱層３の間にはＳｉＯ２粉を充填した。鋳型４内には、低純度Ｓｉ（所謂金属Ｓｉ）を１００ｋｇ挿入した。 The mold 4 is formed by assembling a 15 mm-thick SiC plate so that a space with a side of 500 mm and a height of 400 mm can be secured inside, and further applying a 3 mm-thick SiO 2 layer (release layer 5) on the inner surface. did. The space between the mold 4 and the heat insulating layer 3 was filled with SiO 2 powder. 100 kg of low-purity Si (so-called metal Si) was inserted into the mold 4.
鋳型４の底面とステンレス製水冷板９の間にＡｌ２Ｏ３製断熱材８を挟み、Ａｒガス導入管１０により、Ａｒガスを１０Ｌ／ｍｉｎ（リットル／分）流しながら、昇温を開始した。また、装置内から流出するＡｒガスに対する酸素ガス濃度を計測した。Ｓｉを溶解した後、３０分程度溶湯温度が１５００℃に均一になるように保持した。 The Al 2 O 3 heat insulating material 8 was sandwiched between the bottom surface of the mold 4 and the stainless steel water-cooled plate 9, and heating was started while Ar gas was introduced at 10 L / min (liter / min) through the Ar gas introduction pipe 10. . Moreover, the oxygen gas concentration with respect to Ar gas which flows out out of the apparatus was measured. After melting Si, the molten metal temperature was kept uniform at 1500 ° C. for about 30 minutes.
その後、断熱材８を抜いて、水冷板９を鋳型底面に接触させ、凝固率が７０％までは高さ方向の凝固速度が０．３ｍｍ／ｍｉｎに、７０％から１００％までは０．１ｍｍ／ｍｉｎとなるように、ヒータ２に印加する電力を制御しながら、凝固させた。その結果、装置内に混入する炉体容積当りの酸素ガス量は０．１ｍｏｌ／ｍ３・ｍｉｎ以下で、Ｓｉの酸化量は無視できるものであった。また、凝固Ｓｉ全体の９０％以上で、表１に示すＦｅ（鉄）、Ａｌ（アルミニウム）濃度の部分を確保できた。 Thereafter, the heat insulating material 8 is pulled out, the water cooling plate 9 is brought into contact with the bottom of the mold, the solidification rate in the height direction is 0.3 mm / min until the solidification rate is 70%, and 0.1 mm from 70% to 100%. It was solidified while controlling the electric power applied to the heater 2 so as to be / min. As a result, the amount of oxygen gas per furnace volume mixed in the apparatus was 0.1 mol / m 3 · min or less, and the oxidation amount of Si was negligible. Moreover, the part of Fe (iron) and Al (aluminum) density | concentration shown in Table 1 was able to be ensured in 90% or more of the whole solidification Si.
（比較例１）
実施例１と同様の実験を、鋳型の材質をＣに変えて行った。Ｃ製鋳型４は、内側に一辺が５００ｍｍで高さ４００ｍｍの空間が確保できるように、厚さ１５ｍｍのＣ板を組んで、さらに、内面に厚さ３ｍｍのＳｉＯ２層を塗布した。その結果、装置内に混入する炉体容積当りの酸素ガス量は０．１ｍｏｌ／ｍ３・ｍｉｎ以下で、Ｓｉの酸化量は無視でき、凝固Ｓｉの純度も実施例１と同じであった。しかしながら、Ｃ製鋳型の特に上部の酸化による損耗が激しく、さらに、鋳型表面が酸化しガス化してしまうため、塗布したＳｉＯ２層が剥離して、鋳型と溶融Ｓｉとが付着してしまい、凝固Ｓｉを離型させることができなかった。
(Comparative Example 1)
The same experiment as in Example 1 was performed by changing the material of the mold to C. The C mold 4 was formed by assembling a C plate having a thickness of 15 mm so that a space having a side of 500 mm and a height of 400 mm could be secured on the inner side, and an SiO 2 layer having a thickness of 3 mm was applied to the inner surface. As a result, the amount of oxygen gas per furnace volume mixed in the apparatus was 0.1 mol / m 3 · min or less, the amount of oxidation of Si was negligible, and the purity of solidified Si was the same as in Example 1. However, the wear due to oxidation of the upper part of the C mold is particularly severe, and further, the mold surface is oxidized and gasified, so that the applied SiO 2 layer is peeled off, and the mold and the molten Si adhere to each other and solidify. Si could not be released.
（実施例２）
図４に示した装置において、一辺が１．２ｍステンレス製炉体１の内面に厚さ１００ｍｍのＡｌ２Ｏ３製断熱層３が充填され、その内側上方に、直径２０ｍｍで、発熱体の部分が７００ｍｍのＳｉＣヒータ２を６本ずつ、垂直になるように２段に分けて配置し、ＳｉＯ２製漏斗１３をヒータと接触しないように、ステンレス製炉体１上面から挿入した。鋳型４は、内側に一辺が４５０ｍｍで高さ４００ｍｍの空間が確保できるように、厚さ５０ｍｍのＡｌ２Ｏ３製煉瓦を組んで、さらに、内面に厚さ１０ｍｍのＳｉＯ２層を塗布した。尚、鋳型４と断熱層３の間にはＳｉＯ２粉を充填した。
(Example 2)
In the apparatus shown in FIG. 4, a 100 m thick Al 2 O 3 heat insulating layer 3 is filled on the inner surface of a stainless steel furnace body 1 having a side of 1.2 m. Six 700 mm SiC heaters 2 were arranged in two stages so as to be vertical, and the SiO 2 funnel 13 was inserted from the upper surface of the stainless steel furnace body 1 so as not to contact the heater. The mold 4 was constructed by assembling a 50 mm thick Al 2 O 3 brick so that a space with a side of 450 mm and a height of 400 mm could be secured on the inner side, and a 10 mm thick SiO 2 layer was applied to the inner surface. The space between the mold 4 and the heat insulating layer 3 was filled with SiO 2 powder.
鋳型４の底面とステンレス製水冷板９の間にＡｌ２Ｏ３製断熱材８を挟み、漏斗１３の上には、Ａｌ２Ｏ３製断熱材を内面に接着したステンレス製の蓋をして、Ａｒガス導入管１０により、Ａｒガスを１０Ｌ／ｍｉｎ流しながら、昇温を開始した。また、装置内から流出するＡｒガスに対する酸素ガス濃度を計測した。 An Al 2 O 3 heat insulating material 8 is sandwiched between the bottom surface of the mold 4 and the stainless steel water-cooled plate 9, and a stainless steel lid having an Al 2 O 3 heat insulating material bonded to the inner surface is put on the funnel 13. The temperature increase was started while flowing Ar gas at 10 L / min through the Ar gas introduction pipe 10. Moreover, the oxygen gas concentration with respect to Ar gas which flows out out of the apparatus was measured.
容器１１内で、金属Ｓｉ中のＢやＡｌが除去された予備精製Ｓｉ８０ｋｇを、漏斗１３上の蓋をはずした後、漏斗１３を経由させて鋳型４に注湯した。注湯後、素早く漏斗１３上に蓋を戻して、３０分程度溶湯温度が１５００℃になるように保持した。 In the container 11, 80 kg of prepurified Si from which B or Al in the metal Si was removed was poured into the mold 4 through the funnel 13 after removing the lid on the funnel 13. After pouring, the lid was quickly returned onto the funnel 13, and the molten metal temperature was maintained at 1500 ° C. for about 30 minutes.
その後、断熱材８を抜いて、水冷板９を鋳型底面に接触させ、凝固率が７０％までは高さ方向の凝固速度が０．３ｍｍ／ｍｉｎに、７０％から１００％までは０．１ｍｍ／ｍｉｎとなるように、ヒータ２に印加する電力を制御しながら、凝固させた。装置内に混入する酸素ガス量は０．１ｍｏｌ／ｍ３・ｍｉｎ以下で、溶融Ｓｉを注湯した直後もほとんど変化が見られず、Ｓｉの酸化量は無視できるものであった。また、凝固後のＳｉは装置内でのＢ汚染はなく、凝固Ｓｉ全体の９０％以上で、表１に示すＦｅ、Ａｌ濃度の部分を確保できた。 Thereafter, the heat insulating material 8 is pulled out, the water cooling plate 9 is brought into contact with the bottom of the mold, the solidification rate in the height direction is 0.3 mm / min until the solidification rate is 70%, and 0.1 mm from 70% to 100%. It was solidified while controlling the electric power applied to the heater 2 so as to be / min. The amount of oxygen gas mixed in the apparatus was 0.1 mol / m 3 · min or less, almost no change was observed immediately after pouring molten Si, and the amount of oxidation of Si was negligible. Further, the solidified Si was free from B contamination in the apparatus, and 90% or more of the entire solidified Si could secure the Fe and Al concentration portions shown in Table 1.
１ 炉体、
２ ヒータ、
３ 断熱層、
４ 鋳型、
５ 離型層、
６ 固体Ｓｉ、
７ 断熱層、
８ 断熱材、
９ 水冷板、
１０ Ａｒ導入管、
１１ 溶解又は予備精製用容器、
１２ 溶融Ｓｉ、
１３ 漏斗。
1 furnace body,
2 heaters,
3 heat insulation layer,
4 molds,
5 release layer,
6 Solid Si,
7 heat insulation layer,
8 Insulation,
9 Water cooling plate,
10 Ar inlet tube,
11 Dissolution or prepurification containers,
12 Molten Si,
13 Funnel.
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| JPS6379794A (en) * | 1986-07-10 | 1988-04-09 | テキサス インスツルメンツ インコ−ポレイテツド | Material treatment furnace and method of forming single crystal silicon sphere |
| JPS63166711A (en) * | 1986-12-26 | 1988-07-09 | Osaka Titanium Seizo Kk | Production of polycrystalline silicon ingot |
| JPS6461309A (en) * | 1987-09-01 | 1989-03-08 | Showa Aluminum Corp | Purification of silicon |
| JP2846408B2 (en) * | 1990-05-30 | 1999-01-13 | 川崎製鉄株式会社 | Silicon purification method |
| JPH07277722A (en) * | 1994-02-16 | 1995-10-24 | Sumitomo Chem Co Ltd | Method for purifying silicon |
| JP3523986B2 (en) * | 1997-07-02 | 2004-04-26 | シャープ株式会社 | Method and apparatus for manufacturing polycrystalline semiconductor |
| JP4003271B2 (en) * | 1998-01-12 | 2007-11-07 | Ｊｆｅスチール株式会社 | Silicon unidirectional solidification equipment |
| JP4132649B2 (en) * | 2000-12-05 | 2008-08-13 | シャープ株式会社 | Purification method for molten silicon |
-
2005
- 2005-02-08 JP JP2005032115A patent/JP4766882B2/en not_active Expired - Fee Related
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| JP2006219313A (en) | 2006-08-24 |
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