| Abstract: | 在製造矽晶圓過程中，切割步驟造成了大量的廢料產生以及矽原料浪費；因此，除了回收廢料中具有高經濟價值的碳化矽研磨粒子外，隨著矽原料價格日漸攀升，回收切損的矽變得越來越重要。本研究探討電場下，矽與研磨粒子的分離機制，並分析實際工廠產出的切割廢料在電場促進下的分離效果。研究可分為五個部份；首先，以矽與碳化矽粒子混合來模擬矽泥，測量兩種粒子的特性差異，以作為設計分離槽的計算依據；之後，運用在實際分離工廠之切割廢料，並研究不同酸鹼值下的分離效果。依照原始分離槽的缺失改良其結構，比較兩種水槽處理工廠切割廢料的效果；於矽與碳化矽分離後，分析其中金屬的移除情形，並提升金屬移除率；最後，以矽與氧化鋁混合來模擬矽泥，並評估其分離效果。根據欲分離的粒子特性差異與理論計算得知，分離期間粒子沈降的終端速度、角度與橫向位移會受到密度、粒徑大小以及表面帶電性質等因素的影響，以致分離效果不同。在適當的參數條件下，實際分離工廠切割廢料中的矽與碳化矽，可使回收的碳化矽含量由原來的72 wt.%提高到90 wt.%；而回收的矽含量亦可由原來的24 wt.%提高到91 wt.%。同時，兩者的鐵含量亦可在作用後大幅下降，達到無法以離子偶合電漿設備檢出的效果，即濃度低於1ppb。比較矽與氧化鋁以及矽與碳化矽的分離效果發現，同樣粒徑差異的範圍下，由於矽與氧化鋁間的表面帶電差異較矽與碳化矽大，因此分離效果較好。本研究使用的分離方法免除了有毒物質與強酸的使用，並可在回收矽及研磨粒子期間，同時將含鐵的金屬雜質移除。
In silicon wafer manufacturing, a large number of sawing waste and silicon kerf loss were produced during cutting process. Therefore, in addition to recovering the abrasives with high economic value, silicon carbide, recycling silicon kerf may be a good solution to reduce the high cost of silicon feedstock for solar cells. This study investigated recovery of silicon and abrasives from sawing waste using electric field. The experiments can be divided into the following parts, including separation of silicon and silicon carbide of simulated slurry and plant slurry, in two tank with different structures; metal removal from sawing waste. Finally, instead of silicon carbide, the separation of silicon and alumina was also studied herein. According to the properties of particles and theoretical calculation, the moving velocity, angle and horizontal displacement of settling particles will be subject to density, particle size, charges on surface, resulting in different separation performance. The experimental results showed with appropriate conditions, the contents of silicon and silicon carbide in separated powders would be increased, where silicon carbide content could increase from 72 wt.% of original plant slurry to 91 wt.%, and silicon content could increase from the 24 wt.% to 90 wt.%. At the same time, iron could also be removed, and its content was below the detected limiting of ion-coupled plasma instrument (1 ppb). It was found separation performance of silicon and alumina was better than that of silicon and silicon carbide due to the larger charged difference between silicon and alumina than that between silicon and silicon carbide. Instead of using toxic medium or strong acid, herein, the recovery of silicon and silicon carbide with electric field was proved, and iron impurities were removed at the same time. |
