201204883 六、發明說明： 【發明所屬之技術領域】 本發明是有關於一種作為太陽電池用基板的素材的矽 錠（silicon ingot)的連續鑄造方法。 【先前技術】 近年來，由C02排放引起的全球暖化問題或能源 (energy resource)的枯竭問題變得嚴重，作為這些問題的 對策之一 ’活用無限地直射的太陽光的能量的太陽光發電 受到關注。太陽光發電是使用太陽電池來將太陽光的能量 直接轉換為電力的發電方式’將多結晶的矽晶圓用作太陽 電池的基板已成為主流。 將單向性凝固的^夕旋作為素材，對該石夕鍵進行截塊 (slice)’從而製造太陽電池用的多晶矽晶圓。因此，為了 實現太陽電池的普及，必須確保矽晶圓的品質並且減少成 本（cost)，且要求於前階段中，廉價地製造高品質的矽錠。 作為可應對上述要求的方法，利用電磁感應的連續鑄造方 法即電磁鑄造法已被實際運用。 圖5是模式性地表示電磁鑄造法中所使用的先前的電 磁鑄造裝置的構成的圖。如圖5所示，電磁鑄造裝置包括 腔室（chamber) 1。該腔室1是使内部與外氣隔離且將内 部維持為適合於鑄造的惰性氣體環境的雙重壁構造的水冷 各益°未圖示的原料供給裝置經由可開閉的擋閘（shutter) 2而連結於腔室1的上壁。腔室1於上壁設置有惰性氣體 導入口 5，於底壁設置有排氣口 6。 201204883l 於腔室1内，配置有無底冷卻坩堝7、感應線圈（c〇il) 8、第1後熱器（after heater) 9a以及第2後熱器％。冷 卻坩堝7不僅作為熔解容器而發揮功能，亦作為鑄模而^ 揮功能，該冷卻坩堝7為導熱性以及導電性優異的金屬（例 如銅）製的角筒體，且懸吊於腔室丨内。該冷卻坩堝7將 上部予以保留而於圓周方向上分割為多個帶狀的元件藉 由在内部流通的冷卻水來對該冷卻坩堝7進行強制冷卻。9 感應線圈8是以圍繞冷卻坩堝7的方式，與冷卻坩堝 7同芯地繞設於該冷卻坩堝7，且連接於未圖示的電源裝 置。由加熱器或保溫材料構成的後熱器9a及％是與冷卻 坩堝7同芯地連續設置於冷卻坩堝7的下方，對自卻 坩堝7下拉的矽錠3進行加熱，使矽錠3的軸方向產生適 當的溫度梯度。 又，於腔室1内，在連結於原料供給裝置的擋閘2的 下方安裝有原料導入管10。隨著擋閘2的開閉，粒狀或塊 狀的矽原料自原料供給裝置供給至原料導入管1〇内接著 裝入至冷卻掛瑪7内。 於腔室1的底壁上’在第2後熱器％的正下方設置有 用以將晶錠3予以抽出的抽出口 4，該抽出口 4被=體密 封著。晶錠3 —方面受到貫穿抽出口 4而下降的支持台ι4 支持’一方面被下拉。 ' 於冷卻坩堝7的正上方，以可升降的方式設置有電漿 炬（plasma torch) 13。該電漿炬13連接於未圖示的電漿 電源裝置的-極’該電驗丨3的另—極連接於晶鍵3側。 201204883 該電漿炬13以下降的狀態而插入至冷卻坩堝7内。 於如上所述的使用電磁鑄造裝置的電磁鑄造法中，將 石夕原料裝入至冷卻掛禍7’將父流電流施加至感應線圈8， 並且對下降的電漿炬13進行通電。此時，由於構成冷卻坩 堝7的帶狀的各元件彼此被電性分割，因此，隨著由感應 線圈8引起的電磁感應，於各元件内產生渦電流（Μ# CUrrent) ’冷卻坩堝7的内壁側的渦電流使冷卻坩堝7内產 生磁場。藉此，冷卻坩堝7内的矽原料受到電磁感應加熱 而熔解，從而形成熔融矽12°又，於電漿炬13與矽原料 ，間’進而於電漿炬13與溶㈣12之間產生電聚弧 (plasmaarc)，藉由該電漿弧的焦耳熱（J〇uieheat)來對 2料進行加熱，使财原料_，減輕電磁感應加熱的 負擔’從而效率良好地形成熔融矽12。 絡融石7 -一 V “巧用件隨冷部坩堝7的内壁的渦電流而產 =磁場、以及⑽_ 12的表面產生的電流之間的相互 用’於炫融妙12的表面的内側法線方向上承受力（捏 (rmm因此，該熔㈣12割林與冷卻_7 ^ ^觸的狀態:於冷卻賴7内，若一方面切原料溶解 面使支持麵辦u的核纟M緩慢 ==圈8的下端，感應磁場會變小，因此，發 12自外卿It柄藉由冷卻_ 7的冷卻作用，熔融; 。接著，隨著支持台14的下降，如 [Λ二予以裝入’且持續地進行熔解以及凝固，藉此 炼融石夕12朝—個方向凝固，物連續地鑄^出晶ί 3 6 20120488¾ 於連續鑄造過程中，為了將腔室i内維持為惰性氣體 環境，將氬或氮等的惰性氣體依序供給至熔融矽12的上 4 ’使上述h性氣體充滿於腔室1内。如圖5的塗黑箭頭 所示，自設置於電漿炬13的前端或腔室i的上壁的惰性氣 體導入口 5、以及用以將原料予以導入的擋閘2來供給惰 性氣體。 腔室1於第1後熱器9a與第2後熱器9b之間，設置 有劃分腔室1的上部與下部的劃分部la。又，在腔室i的 上部與下部形成開口的配管15連結於腔室丨的侧壁，一方 面經由該配管15而將供給至熔融矽12的上方的惰性氣體 導入至腔室1的下部，一方面進行連續鑄造。另一方面， 腔室1内的環境氣體自設置於腔室丨的底壁的排氣口 6依 序排出。 根據如上所述的電磁鑄造法，由於溶融矽12與冷卻坩 ，7的接觸減輕，因此，可防止伴隨該接觸而受到來自冷 部坩堝7的雜質的污染，從而可獲得高品質的晶錠3。而 且，由於採用連續鑄造，因此，可廉價地製造晶錠3。 關於藉由電磁鑄造法來鑄造矽錠的方法，先前已提出 各種方案，例如有專利文獻丨。於該專利文獻丨中，將在 ，周方向上分割為多個帶狀的元件的冷卻坩堝的分割間隙 設為0.3 mm〜1.0 mm，藉此，可有效果地抑制熔解矽進入 至帶狀的元件的間隙中而固化的情形，即，可有效果地抑 制所謂的滲入。 於專利文獻1所揭示的矽錠的連續鑄造方法中，惰性 201204883 氣體是自設置於腔室的上部側壁的導人卩供給至溶解石夕的 上方，接著自設置於腔室的下部側壁的排氣口排出。 [先行技術文獻] [專利文獻] [專利文獻1]日本專利特開平1-264920號公報 當藉由電磁鑄造法來連續地縳造矽錠時，若晶旋受到 如Fe或Ni等的雜質的污染，則所鑄造的晶錠的品質會降 低。因此，當藉由電磁鑄造法來連續地鑄造矽錠時，必須 儘可能地減少由雜質引起的污染。 上述先前的矽錠的連續鑄造方法是自設置於腔室的上 部的惰性氣體的導入口或電漿炬、以及用以將原料予以導 入的擂閘，將惰性氣體供給至熔融矽的上方。於該情形時， 所鑄造的晶錠的外周部會受到雜質的污染。 【發明内容】 本發明是鑒於如上所述的狀況而成的發明，目的在於 提供一種可使由晶錠的外周部的雜質引起的污染減少的矽 鍵的連續禱造方法。 當藉由電磁鑄造法來連續鑄造矽錠時，配置於腔室内 的加熱器、或保溫材料、以及對上述構件進行固定的金屬 構件等的爐内零件會因加熱而將雜質釋放至環境氣體中。 本發明者考慮到當一方面自無底冷卻坩堝下拉熔融矽，一 方面使該縣残固時，上述釋放至環境氣體中的雜質會 污染晶錠的外周部，藉由使用有限元素法（finite咖麵t method)的分析來對腔室内的環境氣體的流路進行了調查。 8 201204883ι 腔室内的環境氣體的流路的分析是利用上述圖 5所示 的電磁鑄^裝置來進行，將來自惰性氣體導入口 5的5〇 Ι/mm的流量的Ar氣體、來自電聚炬13的1〇〇 1/min的流 量的Ar氣體以及來自擋閘2的5G 1/min的流量的Ar氣體 =給至溶融料上方。另—方面將環境氣體自設置於腔 至的下1的排氣口 6排出，使腔室内的壓力保持為 1.044x10 Pa。又’將感應線圈8的發熱量設為36〇 kw〜 390kW ’將電漿炬13產生的電漿弧的發熱量設為12〇讀 〜130kW 〇 圖6是表示先前的矽錠的連續鑄造法中的腔室内的環 境氣體㈣路的模_。圖6赋性地表示與腔室内的環 境氣體的流路相_分析結果，以實線箭頭來表示流速為 1.0 m/s以上的流路。根據圖6所示的結果可知··供給至熔 融石夕12的上方的惰性氣體的大部分經由配管15而流動至 腔室的下部之後，自排氣口排出。又，已破認 •於晶的 外周’無流速超過1.0 m/s的環境氣體的流路，環境氣體停 滯。 士本發明者認為：由於在晶錠的外周，幾乎無環境氣體 的流路’目此’輯造的晶錠外周部的污染受後熱器的影 響大’該後熱器是配置為圍繞下拉的晶錠，對該晶錠進行 加熱而使提拉轴方向上產生適當的溫度梯度。 圖7是作為先前的石夕键的連續鎢造方法中的環境對石夕 鍵的外周部造成污染的污染例，表示了由後熱器引起的污 染的模式圖。於圖7中表示了矽錠3、以及對該晶錠進行 201204883 如圄7^1,方向上產生適當的溫度梯度的後熱器9。 圖的魏箭頭所示’雜#自構成後熱器9的加埶器或 而:放至環境氣體中。由於晶錠3的外周的環境 =質：:釋放至環境氣體中的雜質與晶錠發生接 "質混至s曰錠，從而該晶錠的外周部受到污染。 此外本發明者對使B日日錠的外周 氣體的污染減少的方法進行仔細研究之後， 給至石夕_下部，使該惰性氣體峨的外ί k通’藉此’可使環境氣體對於外周部的污染減少。 本發暇基於上述見解而完成的發明，以下 及（2)的矽錠的連續鑄造方法為宗旨。 ⑴-種魏的連續鏵造方法’―方面將惰性氣體供 内，一方面將幾裝入至配置於上述腔室内的 ;==:卻_，藉由來自圍繞無底冷= 的4應線圈的電磁感應加熱來使石夕原料炫解， 底冷卻賴下㈣熔融⑦，―方面使 而、 連續物錠，該方法的特徵在於:當將惰 腔室，，將惰性氣體供給至細夕的上方， =銳的下部’使供給至該下部的惰性氣體於石夕鍵的外周流 (2)如上述⑴所述的矽錠的連續鑄造方法 錠的連續鑄造方法的特徵在於：將上述腔室 = 流入至矽錠的下部的流路予以阻斷。 衣兄虱體 [發明的效果] 201204883 本發明的矽錠的連續鑄造方法是將惰性氣體供給至矽 錠的下部’使潔淨度高的惰性氣體於_朗外周流通，藉 此’於所鑄造的矽錠的外周部，可減少由雜質引起的污染。 ▲為讓本發明之上述和其他㈣、特徵和優點能更明顯 易懂，下文特舉較佳實施例，並配合所附圖式，作詳細說 明如下。 【實施方式】 ^以下基於圖式來對本發明的石夕鍵的連續鑄造方法進 行說明。 圃i疋對本發明的矽錠的連續鑄造方法進行說明的模 式圖。圖1所不的電磁鑄造裝置相對於上述圖5所示的電 磁鑄造褒置，追加了將惰性氣體供給至下拉的晶旋3的 部的導入％•線16、以及將腔室内的環境氣體流人至晶鍵 部的流路予以阻斷的分隔構件17。 —本發明的石夕錠的連續鎢造方法是將惰性氣體供給至腔 =1内’並且料原料裝人至配置於該腔室丨内的 底冷卻㈣7，藉由來自圍繞無底冷卻购^ ^線圈8的電磁感應加熱來使㈣料聽，-方面自益 二、：坩堝7下拉該熔融矽12，一方面使該熔融矽u凝 在於從==:至該_連續铸造方法的特徵 至溶树Λ * 室1 _，將雜氣體供給 ^ 的上方，並且供給至矽錠3的下部，使供給至 该下部的惰減胁魏3❸卜職通。 '。至 將惰性氣體供給至石夕錠3的下部之後，如圖i中的點 201204883 不’所供給的惰性氣體隨著自然職而於雜3 D机通。如此，矽錠3被在外周流通的惰性氣體所遮 献。 2疋對本發明的發㈣連續鑄造方法的遮蔽效果進 二，模式圖。於圖2中’表示有_ 3與後熱器9, 〇!/、器9對上述晶錠進行加熱且在下拉軸方向產生適當 皿=度。本判的魏的連續鑄造法是將惰性氣體供 、、《至曰曰旋3的下部，藉此，如圖 性氣體於晶鍵的外周流通。 便^ 於上述情形時，因加熱而自構成該後熱器9的加熱器 或保溫材_放出的雜質不會停滞於晶錠的外周，而是藉 由在i卜周流通的惰性氣體而朝上方流動。因此，自構成該 後熱器9的加熱器或保溫材料釋放出的雜質的大部分不會 到達由流通的惰性氣體所遮蔽的晶錠表面。利用此種於晶 旋的=周流通的惰性氣體的遮蔽效果，本發明的晶鍵的連 續鱗造方法可使所鑄造的晶錠的外周部的污染減少。 於本發明的矽錠的連續鑄造方法中，當將惰性氣體供 給至晶錠的下部時，可基於如垂直於晶錠的下拉軸的面的 剖面形狀的尺寸或下拉轴方向的長度等的晶錠的尺寸 (二ze)、或腔室i的容積、以及腔室1與後熱器之間的間 隔等’分別適當地對供給至晶錠的下部以及熔融矽的上方 的惰性氣體的流量進行設定。 如上述圖5所示’於先前的電磁鑄造爐中，一般而言， 後熱器9b與腔室1的底壁相隔開。因此，供給至熔融石夕的 12 201204883 、方的惰性氣體、或供給至狀的下部且於日日日錠的外周流 ，的惰性氣體在腔室内㈣之後，有時會流人至晶旋的下 部。此種環境氣體於腔室内流動時，有可能會包含自爐内 零件釋放出的雜質，潔淨度降低，因此，若此種環境&體 流入至晶錠的下部並於㈣的外舰通，則存在污染石夕鍵 的外周部之虞。 因此，對於本發明的矽錠的連續鑄造方法而言，較佳 為將腔室内的環境氣體流入至矽錠的下部的流路予以阻 斷。藉此，僅自腔室外供給的惰性氣體流入至晶錠的下部， 且僅潔淨度高的惰性氣體於晶錠的外周流通，因此，可進 一步使所鑄造的晶錠的外周部的污染減少。作為將腔室内 的環境氣體流入至矽錠的下部的流路予以阻斷的方法，例 如，如上述圖1所示，可使用具有L字型的剖面形狀的圓 筒狀的分隔構件。 【實例】 為了確認本發明的矽鍵的連續鑄造方法的效果，進行 下述的試驗。 [試驗條件] 使用如下的電磁鑄造裝置，藉由電磁鑄造法來鑄造矽 鍵，該電磁铸造裝置自上述圖1所示的電磁鑄造裝置中， 除去了將腔室内的環境氣體流入至石夕錠的下部的流路予以 阻斷的分隔構件17。此時’自導入口 5以20 Ι/min的流量、 自電漿炬13以1〇〇 l/min的流量以及自擋閘2以5〇 1/min 的流量來供給惰性氣體，將供給至熔融矽的上方的惰性氡 13 201204883 體的流量設為170 l/min。又，自導入管線16以30 l/min 的流量將上述惰性氣體供給至晶錠的下部，使該惰性氣體 於晶錠的外周流通。 於比較例中’自導入口 5以20 l/min的流量、自電锻 炬13以1〇〇 l/min的流量以及自擋閘2以5〇 1/min的流量 來將惰性氣體供給至熔融矽的上方，並不自導入管線16 朝晶錠下部供給上述惰性氣體。本發明例以及比較例均是 將環境氣體自設置於腔室的下部的排氣口 6排出，使腔室 内的壓力保持為l.〇44xl〇5pa。 本發明例以及比較例均是在垂直於下拉方向的面上， 將鑄造的矽錠分割為縱向的2個結晶以及橫向的3個結晶 之後，切割為矽晶圓。對所獲得的晶圓的外周區域的雜質 濃度進打測定。關於外周區域中的雜質濃度，將與晶圓的 外周相距2G mm的區域予以切斷，藉由全轉分析來對 以及Νι的濃度進行測定。又，本發明例以及比較例均 疋採用1G枚晶圓來對外周區域中的雜質濃度進行測定。 [試驗結果] 圖3是表示本發明例以及比較例中的晶圓外周區域的 =農度的差異的範_圖。如圖3所示，本發 例相比較，Fe濃度降低。 ”較 n i濃=11 及味射的晶圓相區域的 ^ 、、&圍的圖。如圖4所示，本發明例與比較 例相比較’Ni濃度降低。 ”兴比竿又 因此’對於本發明的石夕錠的連續鑄造方法而言，將惰 201204883 性氣體供給至矽錠的下部，使潔淨度高的惰性氣體於矽錠 的外周流通’藉此，於所鑄造的矽錠的外周部，顯然可減 少由雜質引起的污染。 對於本發明的矽錠的連續鑄造方法而言，將惰性氣體 供給至矽錠的下部，使潔淨度高的惰性氣體於矽錠的外周 流通’藉此’於所鑄造的矽錠的外周部，可減少由雜質引 起的污染。 因此’若將本發明的矽錠的連續鑄造方法應用於太陽 電池用的石夕錠的鑄造’則可大幅度地有助於使太陽電池用 晶圓的品質提高。 …雖然本發明已以較佳實施例揭露如上，然其並非用以 限定本發明，任何熟習此技藝者，在不脫離本發明之精神 =範圍内，當可作些許之更動與潤飾，因此本發明之保護 氣圍當視後社申料利範圍所界定者為準。 【圖式簡單說明】 圖1疋對本發明的矽錠的連續鑄造方法進行說明的模 行說明的口 Γ 的連續缚造方法的遮蔽效果進 &二；=及比較例㈣晶圓外周區域的 姐鮮丨巾㈣圓相區域的 圖5是模式性地表示電磁鱗造法中所使用的先前的電 201204883 磁鑄造裝置的構成的圖。 圖6是表示先前的矽錠的連續鑄造法中的腔室内的環 境氣體的流路的模式圖。 圖7是作為先前的矽錠的連續鑄造方法中的環境對矽 錠的外周部造成污染的污染例，表示了由後熱器引起的污 染的模式圖。 【主要元件符號說明】 1 :腔室 la :劃分部 2 :擋閘 3:矽錠或晶鍵 4 :抽出口 5:惰性氣體導入口 6:排氣口 7:無底冷卻坩堝 8:感應線圈 9 :後熱器 9a :第1後熱器 9b :第2後熱器 10 :原料導入管 12 :熔融矽 13 :電漿炬 14 :支持台 15 :配管 201204883ι 16 :惰性氣體導入管線 17 :分隔構件 17201204883 6. OBJECT OF THE INVENTION: TECHNICAL FIELD The present invention relates to a continuous casting method of silicon ingot as a material for a substrate for a solar cell. [Prior Art] In recent years, the problem of global warming caused by CO2 emissions or the depletion of energy resources has become serious. As one of the countermeasures for these problems, solar power generation using the energy of infinitely direct sunlight Having attention. Solar power generation is a power generation method that uses solar cells to directly convert the energy of sunlight into electricity. The use of polycrystalline germanium wafers as substrates for solar cells has become mainstream. A polycrystalline germanium wafer for a solar cell was produced by using a one-way solidification method as a material to slice the stone bond. Therefore, in order to realize the spread of solar cells, it is necessary to ensure the quality of the wafer and reduce the cost, and it is required to manufacture high-quality germanium ingots at a low cost in the previous stage. As a method capable of coping with the above requirements, a continuous casting method using electromagnetic induction, that is, an electromagnetic casting method has been practically used. Fig. 5 is a view schematically showing the configuration of a conventional electromagnetic casting apparatus used in the electromagnetic casting method. As shown in Fig. 5, the electromagnetic casting apparatus includes a chamber 1. The chamber 1 is a water-cooling device that separates the inside from the outside air and maintains the interior in an inert gas atmosphere suitable for casting. The raw material supply device (not shown) is opened via an openable shutter 2 Connected to the upper wall of the chamber 1. The chamber 1 is provided with an inert gas inlet 5 on the upper wall and an exhaust port 6 on the bottom wall. 201204883l In the chamber 1, a bottomless cooling crucible 7, an induction coil 8, a first after heater 9a, and a second afterheater % are disposed. The cooling crucible 7 functions not only as a melting vessel but also as a mold for a metal cylinder (for example, copper) having excellent thermal conductivity and electrical conductivity, and suspended in a chamber. . The cooling crucible 7 retains the upper portion and is divided into a plurality of strip-shaped members in the circumferential direction to forcibly cool the cooling crucible 7 by the cooling water flowing therein. The induction coil 8 is wound around the cooling crucible 7 so as to surround the cooling crucible 7, and is connected to a power supply unit (not shown). The afterheaters 9a and % consisting of a heater or a heat insulating material are continuously disposed below the cooling crucible 7 in the same core as the cooling crucible 7, and the crucible ingot 3 pulled down from the crucible 7 is heated to make the shaft of the crucible ingot 3 The direction produces an appropriate temperature gradient. Further, in the chamber 1, a raw material introduction pipe 10 is attached below the shutter 2 connected to the material supply device. With the opening and closing of the shutter 2, the granular or block-shaped tantalum raw material is supplied from the raw material supply device to the raw material introduction pipe 1 and then loaded into the cooling burr 7. On the bottom wall of the chamber 1, a discharge port 4 for extracting the ingot 3 is disposed directly below the second afterheater %, and the discharge port 4 is sealed by the body. The ingot 3 is supported by the support table ι4 which is lowered through the discharge port 4 and is pulled down on the one hand. Immediately above the cooling crucible 7, a plasma torch 13 is provided in a vertically movable manner. The plasma torch 13 is connected to a - pole of a plasma power supply unit (not shown). The other electrode of the electric detector 3 is connected to the crystal key 3 side. 201204883 The plasma torch 13 is inserted into the cooling crucible 7 in a lowered state. In the electromagnetic casting method using the electromagnetic casting device as described above, the raw material is applied to the induction coil 8 by charging the material of the stone material to the cooling coil, and the falling plasma torch 13 is energized. At this time, since the strip-shaped elements constituting the cooling crucible 7 are electrically divided from each other, eddy current is generated in each element along with electromagnetic induction by the induction coil 8 (Μ#CUrrent) 'cooling 坩埚7 The eddy current on the inner wall side causes a magnetic field to be generated in the cooling crucible 7. Thereby, the crucible material in the cooling crucible 7 is melted by electromagnetic induction heating to form a melting crucible 12°, and between the electric plasma torch 13 and the crucible raw material, the electromagnet is generated between the plasma torch 13 and the dissolved gas (four) 12 . In the arcacol, the material is heated by the Joule heat of the plasma arc to reduce the burden of electromagnetic induction heating, thereby efficiently forming the melting crucible 12. The fused stone 7-one V "the use of the eddy current with the inner wall of the cold section =7 = the magnetic field, and the current generated by the surface of the (10) _ 12 is used in the inner side of the surface of the sleek The force is applied in the direction of the line (rmm (rmm, therefore, the melting (four) 12 cut forest and cooling _7 ^ ^ touch state: in the cooling lag 7, if the raw material dissolves the surface on one hand, the support surface does u the core 纟M slow = = the lower end of the circle 8, the induced magnetic field will become smaller, therefore, the hair 12 is melted by the cooling effect of the cooling _7; then, as the support table 14 is lowered, as the [2] is loaded 'And continuously melt and solidify, thereby solidifying in the direction of the smelting stone 12, and continuously casting the crystal. 3 6 201204883⁄4 In the continuous casting process, in order to maintain the inside of the chamber i as an inert gas atmosphere An inert gas such as argon or nitrogen is sequentially supplied to the upper 4' of the melting crucible 12 to fill the chamber 1 with the above-mentioned helium gas. As shown by the black arrow in Fig. 5, it is provided from the plasma torch 13 The inert gas introduction port 5 of the upper wall of the front end or the chamber i, and the shutter 2 for introducing the raw material are supplied. The chamber 1 is provided between the first afterheater 9a and the second afterheater 9b, and is provided with a partitioning portion 1a that partitions the upper and lower portions of the chamber 1. Further, an opening is formed in the upper and lower portions of the chamber i. The piping 15 is connected to the side wall of the chamber, and the inert gas supplied to the upper side of the melting crucible 12 is introduced into the lower portion of the chamber 1 via the piping 15, and continuous casting is performed on the one hand. The ambient gas in 1 is sequentially discharged from the exhaust port 6 provided in the bottom wall of the chamber 。. According to the electromagnetic casting method as described above, since the contact between the molten crucible 12 and the cooling crucible 7 is reduced, it is possible to prevent the accompanying This contact is contaminated by impurities from the cold portion 7 to obtain a high-quality ingot 3. Further, since continuous casting is used, the ingot 3 can be produced at low cost. About casting by a magnetic casting method In the method of the ingot, various proposals have been made, for example, in the patent document, in which the dividing gap of the cooling crucible divided into a plurality of strip-shaped elements in the circumferential direction is set to 0.3 mm to 1.0 mm. With this, there may be In a continuous casting method of the bismuth ingot disclosed in Patent Document 1, the inert gas 201204883 gas is self-inhibited by suppressing the melting of the enthalpy into the gap of the strip-shaped element and solidifying. The guide hole provided on the upper side wall of the chamber is supplied to the upper side of the dissolved stone, and then discharged from the exhaust port provided on the lower side wall of the chamber. [Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent Japanese Laid-Open Patent Publication No. H1-264920 discloses that when a tantalum ingot is continuously bound by an electromagnetic casting method, if the crystal spin is contaminated with impurities such as Fe or Ni, the quality of the cast ingot is lowered. When the tantalum ingot is continuously cast by the electromagnetic casting method, it is necessary to reduce the contamination caused by the impurities as much as possible. The above-described continuous casting method of the bismuth ingot is an inert gas introduction port or a plasma torch provided at the upper portion of the chamber, and a gate for introducing the raw material, and an inert gas is supplied above the melting crucible. In this case, the outer peripheral portion of the cast ingot is contaminated with impurities. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the invention is to provide a continuous praying method for reducing a defect caused by impurities in an outer peripheral portion of an ingot. When the tantalum ingot is continuously cast by the electromagnetic casting method, the heater disposed in the chamber, or the heat insulating material, and the in-furnace parts of the metal member to which the member is fixed may be released into the ambient gas by heating. . The inventors of the present invention have considered that, on the one hand, when the county is refrigerated from the bottomless cooling, the impurities released into the ambient gas may contaminate the outer periphery of the ingot by using the finite element method (finite). The analysis of the coffee surface method was conducted to investigate the flow path of the ambient gas in the chamber. 8 201204883 The analysis of the flow path of the ambient gas in the chamber is performed by the electromagnetic casting apparatus shown in Fig. 5 described above, and the Ar gas of the flow rate of 5 〇Ι/mm from the inert gas introduction port 5 is derived from the electric torch. An Ar gas of a flow rate of 13 〇〇 1 min and a flow rate of Ar gas of a flow rate of 5 G 1 / min from the gate 2 were supplied to the upper of the molten material. On the other hand, the ambient gas is discharged from the exhaust port 6 of the lower one to the cavity, so that the pressure in the chamber is maintained at 1.044 x 10 Pa. Further, the heat generation amount of the induction coil 8 is set to 36 〇 kw to 390 kW. The heat generation amount of the plasma arc generated by the plasma torch 13 is set to 12 〜 to 130 kW. FIG. 6 is a continuous casting method for the prior bismuth ingot. The mode of the ambient gas (four) road in the chamber. Fig. 6 is an explanatory view showing the flow path phase of the ambient gas in the chamber, and the flow path of the flow velocity of 1.0 m/s or more is indicated by a solid arrow. As is apparent from the results shown in Fig. 6, most of the inert gas supplied to the upper portion of the melting stone 12 flows to the lower portion of the chamber through the pipe 15, and is discharged from the exhaust port. In addition, it has been confirmed that the outer circumference of Yujing has no flow path of ambient gas with a flow rate exceeding 1.0 m/s, and the ambient gas is stagnant. The inventor of the present invention believes that since the outer periphery of the ingot is almost free of ambient gas, the contamination of the outer periphery of the ingot is greatly affected by the post-heater. The post-heater is configured to be pulled down. The ingot is heated to produce an appropriate temperature gradient in the direction of the pulling axis. Fig. 7 is a view showing a pollution example in which the environment in the continuous tungsten manufacturing method of the prior Shih-hsing method causes contamination of the outer peripheral portion of the Shih-hsien, and shows a pattern of contamination by the afterheater. In Fig. 7, a crucible 3 is shown, and an afterheater 9 is formed which in the ingot is subjected to an appropriate temperature gradient in the direction of 201204883, such as 圄7^1. The "hybrid" indicated by the arrow in the figure is from the twister of the post-heater 9 or placed in the ambient gas. Due to the environment of the outer periphery of the ingot 3, the impurities released into the ambient gas are connected to the ingot and mixed with the ingot, so that the outer peripheral portion of the ingot is contaminated. Further, the inventors of the present invention carefully studied the method of reducing the contamination of the peripheral gas of the B-day ingot, and then gave it to the lower part, so that the external gas of the inert gas was 'by this' to make the ambient gas to the periphery. The pollution of the Ministry is reduced. The present invention has been completed based on the above findings, and the continuous casting method of the bismuth ingot of the following (2) is aimed at. (1) - The continuous manufacturing method of the kind of Wei's - the inert gas is supplied to the inside, on the one hand, a few are placed in the chamber; ==: but _, by the 4 coils from the bottomless cold = Electromagnetic induction heating to make the Shixi raw material dazzle, the bottom cooling depends on (4) melting 7, the aspect makes the continuous ingot, the method is characterized in that when the inert chamber is supplied, the inert gas is supplied to the fine eve Above, = sharp lower portion 'the outer peripheral flow of the inert gas supplied to the lower portion to the outer core (2) The continuous casting method of the ingot of the tantalum ingot according to the above (1) is characterized in that the chamber is = The flow path that flows into the lower part of the bismuth ingot is blocked.衣衣虱体 [Effect of the invention] 201204883 The continuous casting method of the bismuth ingot of the present invention is to supply an inert gas to the lower portion of the bismuth ingot. The outer peripheral portion of the ingot can reduce contamination caused by impurities. The above and other aspects, features and advantages of the present invention will become more apparent from the following description. [Embodiment] The following is a description of a continuous casting method of the Shi Xi key of the present invention based on the drawings. A schematic diagram for explaining a continuous casting method of the bismuth ingot of the present invention. In the electromagnetic casting apparatus shown in Fig. 1, an introduction of the inert gas to the portion of the spinner 3 where the inert gas is supplied is added, and the ambient gas flow in the chamber is added to the electromagnetic casting device shown in Fig. 5 . The partition member 17 that blocks the flow path from the person to the crystal key portion. - The continuous tungsten production method of the present invention is to supply an inert gas to the cavity = 1 and to feed the raw material to the bottom cooling (4) 7 disposed in the chamber, by purchasing from the bottomless cooling. ^ Electromagnetic induction heating of the coil 8 to make (4) material to listen, - the aspect of self-interest 2: 坩埚 7 pull down the melting enthalpy 12, on the one hand, the melting 矽u condenses in the characteristics from ==: to the _ continuous casting method to The dissolved tree Λ * chamber 1 _, the gas is supplied to the upper side of the crucible 3 and supplied to the lower portion of the crucible ingot 3, so that the inertia is supplied to the lower portion. '. After the inert gas is supplied to the lower portion of the stone slab 3, the inert gas supplied at the point of 201204883 does not pass through the natural environment. Thus, the crucible ingot 3 is covered by an inert gas which flows around the periphery. 2疋 The shielding effect of the hair (four) continuous casting method of the present invention is further shown in Fig. 2 . In Fig. 2, _3 and the afterheater 9, 〇!/, 9 are heated to the above ingot and the appropriate dish = degree is generated in the direction of the pull-down axis. The continuous casting method of Wei in this judgment is to supply an inert gas to the lower portion of the cyclone 3, whereby the pattern gas flows around the periphery of the crystal bond. In the above case, the heat emitted from the heater or the heat insulating material constituting the afterheater 9 does not stagnate on the outer circumference of the ingot, but is caused by the inert gas flowing in the periphery of the ingot. Flowing above. Therefore, most of the impurities released from the heater or the heat insulating material constituting the afterheater 9 do not reach the surface of the ingot which is shielded by the circulating inert gas. By the shielding effect of the inert gas flowing in the cycle of the crystal rotation, the continuous scale forming method of the crystal bond of the present invention can reduce the contamination of the outer peripheral portion of the cast ingot. In the continuous casting method of the bismuth ingot of the present invention, when an inert gas is supplied to the lower portion of the ingot, the crystal may be based on the size of the cross-sectional shape of the face perpendicular to the pull-down axis of the ingot or the length of the pull-down axis direction. The size of the ingot (two ze), or the volume of the chamber i, and the interval between the chamber 1 and the afterheater, etc., respectively, appropriately flow the flow rate of the inert gas supplied to the lower portion of the ingot and above the molten crucible set up. As shown in Fig. 5 above, in the prior electromagnetic casting furnace, in general, the afterheater 9b is spaced apart from the bottom wall of the chamber 1. Therefore, 12 201204883 supplied to the molten stone, the inert gas of the square, or the inert gas supplied to the lower portion of the shape and in the outer circumference of the ingot, sometimes flows into the crystal cyclone after the chamber (4). Lower part. When such an ambient gas flows in the chamber, it may contain impurities released from the furnace parts, and the cleanliness is lowered. Therefore, if such an environment & body flows into the lower part of the ingot and is in the outer ship of (4), Then there is a flaw in the outer peripheral portion of the contaminated Shi Xi bond. Therefore, in the continuous casting method of the bismuth ingot of the present invention, it is preferred that the flow of the ambient gas in the chamber into the lower portion of the bismuth ingot is blocked. Thereby, only the inert gas supplied from the outside of the chamber flows into the lower portion of the ingot, and only the inert gas having a high degree of cleanliness flows around the outer periphery of the ingot, so that the contamination of the outer peripheral portion of the cast ingot can be further reduced. As a method of blocking the flow of the ambient gas in the chamber into the lower portion of the crucible, for example, as shown in Fig. 1 described above, a cylindrical partition member having an L-shaped cross-sectional shape can be used. [Examples] In order to confirm the effects of the continuous casting method of the hydrazone bond of the present invention, the following tests were carried out. [Test conditions] The 矽 key was cast by an electromagnetic casting method using the following electromagnetic casting apparatus, and the electromagnetic casting apparatus was removed from the electromagnetic casting apparatus shown in Fig. 1 to remove the ambient gas in the chamber into the stone slab The lower flow path is blocked by the partition member 17. At this time, the inert gas is supplied from the inlet port 5 at a flow rate of 20 Ι/min, at a flow rate of 1〇〇l/min from the plasma torch 13, and at a flow rate of 5〇1/min from the gate 2, and is supplied to the inert gas. The flow rate of the inert 氡13 201204883 body above the melting enthalpy was set to 170 l/min. Further, the inert gas was supplied to the lower portion of the ingot from the introduction line 16 at a flow rate of 30 l/min, and the inert gas was allowed to flow around the outer periphery of the ingot. In the comparative example, the inert gas was supplied to the inlet port 5 at a flow rate of 20 l/min, the electric forging torch 13 at a flow rate of 1〇〇l/min, and the flow rate from the brake 2 at 5〇1/min. Above the molten crucible, the inert gas is not supplied from the introduction line 16 toward the lower portion of the ingot. In the examples of the present invention and the comparative examples, the ambient gas was discharged from the exhaust port 6 provided at the lower portion of the chamber, and the pressure in the chamber was maintained at 1.4 x 44 x l 〇 5 Pa. In the examples of the present invention and the comparative examples, the cast tantalum ingot was divided into two crystals in the longitudinal direction and three crystals in the transverse direction on the surface perpendicular to the pull-down direction, and then cut into a tantalum wafer. The impurity concentration in the peripheral region of the obtained wafer was measured. Regarding the impurity concentration in the outer peripheral region, a region separated from the outer circumference of the wafer by 2 G mm was cut, and the concentration of Νι was measured by full-turn analysis. Further, in the examples of the present invention and the comparative examples, the concentration of impurities in the peripheral region was measured using a 1 G wafer. [Test Results] Fig. 3 is a graph showing the difference in the agricultural degree of the wafer outer peripheral region in the examples of the present invention and the comparative example. As shown in Fig. 3, the Fe concentration was lowered as compared with the present example. The graph of the sum of the wafer phase regions of the ni-concentration = 11 and the smear is as shown in Fig. 4. As shown in Fig. 4, the example of the present invention is compared with the comparative example, and the 'Ni concentration is lowered. In the continuous casting method of the ingot of the present invention, the inert gas 201204883 is supplied to the lower portion of the crucible ingot, and the inert gas having high cleanliness is allowed to flow on the outer periphery of the crucible ingot. The outer peripheral portion obviously reduces the contamination caused by impurities. In the continuous casting method of the bismuth ingot of the present invention, an inert gas is supplied to the lower portion of the bismuth ingot, and an inert gas having a high degree of cleanliness is circulated to the outer periphery of the bismuth ingot by the inert gas having a high degree of cleanliness. It can reduce the pollution caused by impurities. Therefore, when the continuous casting method of the bismuth ingot of the present invention is applied to the casting of the slab of the solar cell, the quality of the solar cell wafer can be greatly improved. The present invention has been described above by way of a preferred embodiment, and is not intended to limit the invention, and it is to be understood that those skilled in the art can make some modifications and refinements without departing from the spirit of the invention. The protection of the invention shall be subject to the definition of the scope of the company's application. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a masking effect of a continuous method of splicing the description of the continuous casting method of the bismuth ingot of the present invention, and the second outer peripheral region of the wafer Fig. 5 is a view schematically showing the configuration of a prior electric 201204883 magnetic casting apparatus used in the electromagnetic scale manufacturing method. Fig. 6 is a schematic view showing a flow path of an ambient gas in a chamber in a continuous casting method of a conventional bismuth ingot. Fig. 7 is a view showing a pollution example in which contamination of the outer peripheral portion of the ingot is caused by the environment in the continuous casting method of the prior antimony ingot, and shows a pattern of contamination by the afterheater. [Main component symbol description] 1 : Chamber la: Division 2: Barrier 3: 矽 ingot or crystal key 4: Extraction port 5: Inert gas introduction port 6: Exhaust port 7: Bottomless cooling 坩埚 8: Induction coil 9: afterheater 9a: first afterheater 9b: second afterheater 10: raw material introduction pipe 12: melting crucible 13: electric torch 14: support table 15: piping 201204883ι16: inert gas introduction line 17: separation Component 17