以超過濾薄膜結合混凝前處理回收半導體工業之研磨廢水

Abstract

目前半導體積體電路的生產已經到達深次微米階段，因此化學機械研磨的應用也越來越多。然而化學機械研磨的洗滌需要大量的超純水，而台灣目前因為水資源的缺乏，因此化學研磨廢水(CMP)的處理、再利用也愈顯重要。目前大部分的半導體廠都以混凝沈澱方式來去除化學研磨廢水中的砥粒，依照現場操作及試驗結果均顯示，CMP廢水以化學混凝沈澱處理需耗費大量之混凝劑且pH最適操作區間相常狹窄，因此會產生大量污泥且不易操作。至今半導體廠對CMP廢水之處理效果仍不佳。本研究群以超過濾薄膜直接處理研磨廢水，發現顆粒、濁度去除的效果相當良好，但薄膜極易阻塞，流量、質傳係數下降迅速，因此於廢水進入薄膜前採取前處理--混凝。 研究之中利用超過濾薄膜搭配化學混凝處理CMP廢水，針對半導體製程中金屬膜研磨廢水及氧化膜研磨廢水兩種廢水進行混凝實驗，使用的混凝劑為廢水處理常用之氯化鐵及多元氯化鋁，探討混凝劑種類、最佳操作pH值、混凝劑加藥量影響濁度去除與顆粒粒徑成長之關係。結果顯示對於兩種研磨廢水，皆以多元氯化鋁較佳，就金屬膜研磨廢水而言，於pH 4 ~ 6的環境進行混凝，顆粒成長幅度及濁度的去除較佳；而氧化膜研磨廢水於pH 6顆粒成長狀況最佳，濁度的去除亦佳。若混凝操作處於最適pH值範圍，所需的混凝劑量亦會減少。此外，本研究亦將超過濾薄膜結合最適之混凝條件進行連續流測試。結果顯示，混凝的確可增進進濁度、DOC的去除率及減緩質傳係數下降。因此，進行CMP廢水處理時，混凝前處理是必要的。

The development of Deep Submicron requires higher standard of CMP process. Rinses of wafer and ULSI need a large quantity of ultra pure water. Because of the shortage of water sources in Taiwan, the recycle and reuse of the CMP wastewater has become the interest of many researchers. Most Semiconductor Manufacturers adopt chemical coagulation and precipitation to reduce the deep submicron particles from the CMP wastewater. Field experience and results from our previous studies discovered that large amount of coagulant is needed for the chemical coagulation of the CMP wastewater, which generated large quantity of sludge. In addition, to achieve optimal coagulation, the pH must be controlled in a narrow range. The bottleneck of treatment of CMP wastewater made it difficult to recycle and reuse. Now, a study of direct filtration of CMP wastewater by ultrafiltration (UF) showed high efficiency on particle and turbidity removal. However, the membrane is easy to foul without pretreatment-coagulation. In this study, a combination of UF and coagulation will be applied on the treatment of the CMP wastewater. The CMP wastewater will be taken from ULSI facilities in the Hsin-Chu Science-based Industrial Park, which includes metal and oxide CMP wastewaters. The effects of preatment-coagulation on CMP treatment by UF were evaluated. These parameters include types of coagulants, coagulant dosage and pH condition. The results showed that the coagulant, PACl, was more effect to aggregate both of CMP particles than other types of coagulants. The optimal pH condition was from 4 to 6 for the metal CMP wastewater, and pH 6 for the oxide wastewater. The demand of coagulant dosage can be significant reduced when the coagulation performance was under the optimal pH condition. Besides, the study combines UF with optimum coagulation to run pilot. Result indicates that coagulation could enhance removal efficiency of turbidity and DOC. It also turns down the rate of flux decline as well as MTCw. As a result, pretreatment by coagulation is necessary.