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  • 學位論文

切割矽泥回收矽的應用研究

Application of Recycled Silicon from Kerf-loss Silicon Slurry

指導教授 : 藍崇文
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摘要


矽晶圓切割損失的矽泥與鑄碇過的石英坩堝是太陽能產業兩大廢棄物,以全球每年70 GW的產量計算,有約20萬噸的矽泥與40萬顆的廢棄坩堝,造成損失與環境污染。切削矽來自太陽能級晶碇,純度高於商用氮化矽粉,如果這些矽可回收,並製成可重複使用的氮化矽坩堝,將大幅提升矽晶圓品質與電池效率。這不僅改變產業面貌,也落實循環經濟於太陽能產業。太陽光電產業快速發展,2016年產出超過70 GW,而矽晶電池就佔比超過92%。 因此,本論文提出簡單、快速、無毒、易廠內處理的矽泥回收技術,去除掉切割油、研磨顆粒、金屬後,進一步把這些回收矽再利用。並將砂線回收之經驗也應用到鑽石線切割矽泥上。我們利用連續式沉降提純由合作公司提供之砂線切割之矽廢料。並用酸洗沉降清洗金屬與非金屬雜質(主要為硼(B)與磷(P))。本論文將報導放大製程(數公斤)後之數據,而回收矽純度已達4N,並將其應用於回收成矽原料或氮化矽坩堝上。 後續應用分成矽原料與氮化矽坩堝兩大部分。第一部分之應用考慮到,回收矽粉容易提升純度到85wt.%,但要進一步純化到99wt.%較困難。我們提出快速熱處理製程,製程只需數分鐘。適當的條件下,碳化矽顆粒與金屬能輕易地偏析到表面,再經過酸洗即可得高純矽,最佳的回收矽產率超過70wt.%,研究的參數包含溫度、持溫時間與表面氧化程度。第二部分之應用為透過注漿、高溫氮化做成可以回收使用的NBSN(nitrogen-bonded silicon nitride)坩堝與RBSN(reaction-bonded silicon nitride),並重複鑄錠生長。

並列摘要


The circulatory economy has been paid much attention for the sustainable society. However, two major wastes, kerf-loss silicon and used broken quartz crucibles, are produced from the PV industry. This waste not only causes the environmental burden, but also increases the cost for silicon wafers. Two different kerf-loss slurries (SiC and diamond-wire slicing) were obtained from our company partners. Contineous sedimental, and acid washing and sedimental method were used for silicon recycle. The suitable processes for scaling up were proposed. The metal impurities, B and P were also measured and reported here. Although Si could be enriched easily to 85 wt.% from the waste, it was extremely difficult to further increase the purity of over 99 wt.% due to tiny SiC particles and metallic debris. We proposed a novel rapid thermal process, which was about one hundred times faster than the previous high-temperature treatment, to agglomerate Si in a couple minutes from the pretreated solid powder. With proper conditions, SiC particles and metals could be easily segregated to the surface of Si agglomerates. The high purity Si could be obtained by surface etching, and the best recycle yield was over 70 wt.%. The factors, such as temperature, holding time, and the surface oxidation of Si, were further discussed. Finally, we aim to develop feasible processes to recycle the kerf-loss silicon and use it for making high purity Si3N4 crucibles used for multi-crystalline silicon (mc-Si) ingot growth. More importantly, the crucible could be reused for a couple times. In principle, the crucible should be purer than the current quartz crucibles used in industry. Moreover, the impurities decrease after ingot growth.

參考文獻


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