奈米微氣泡浮除技術於半導體工業化學機械研磨廢水處理之應用

Abstract

半導體業中之化學機械研磨廢水中主要含有奈米級之矽氧化物懸浮微粒，其具有相當穩定分散的能力。目前業界一般是以混凝沈澱方法或是薄膜方法來處理。本研究利用溶解空氣浮除法搭配奈米氣泡生成技術，由於其可產生奈米級的氣泡，可增加與CMP廢水中二氧化矽等顆粒接觸的機會。實驗的進行並搭配實驗設計，以求取更有代表性的數據及結果。根據資料顯示，單純調整廢水的pH值，並沒有任何的去除效果。而在浮除過程前先行添加活化劑以及添加捕集劑，可以有效地去除廢水中的奈米等級微粒。最後發現到，控制硫酸鋁在250-321 mg/L，可以控制放流水濁度低於5 NTU以下的程度。而CTAB的效用則不顯著。處理水裡面會殘留TOC，仍待後段設備處理。本研究證明了搭配奈米氣泡產生器的浮除技術可以對CMP廢水中的微細顆粒進行有效率的去除。爾後的研究方向將朝向連續式、多段式浮除處理。

Semiconductor industry has been a sector of importance and leading edge for economy development in Taiwan and elsewhere for the past several decades and in future. Generally, a large number of complex and highly delicate processes are employed in the semiconductor manufacturing. Besides, a large quantity of ultra-pure water is consumed in various washing and cleaning steps of the semiconductor manufacturing processes. This makes semiconductor industry become highly demanding for water use. In the various semiconductor manufacturing processes, chemical mechanical polishing (CMP) is an important technology for global planarization, which has been commonly adopted for integrated circuit (IC) devices below 0.25 □m. It is estimated that CMP process could account for greater than 40% of ultra-pure water consumption in the semiconductor manufacturing as linewidths of IC devices shrink to <100 nm after 2005. Moreover, CMP wastewater is well-known to contain high content of nano-sized particles (SiO2, Al2O3, MnO2 or CeO2) and various chemicals. Therefore, the burgeoning water demand and wastewater generation impose a chilling effect on current and anticipated semiconductor industry growth. For the sustainable development of water resource, it is necessary to reclaim or reuse the huge quantity of CMP wastewater. In Taiwan, a new semiconductor manufactory is required to reclaim 85% of water used in the manufacturing process. However, traditional wastewater treatment methods are costly and cannot meet this requirement. It is necessary to develop the novel technology for water reclamation of semiconductor manufactory. The purpose of this study was to develop an innovative flotation system with a nano-bubble generator for treating and reclaiming CMP wastewater produced by the semiconductor manufacturing.

In this study, the suitable range of operational parameters (pH, activators, collectors and recycle ratio) for the nano-bubble flotation was recommended by the experimental design methods. At first, a fractional factorial design (FFD) was applied to screen the main parameters affecting the performance of nano-bubble flotation. Then the optimization of these main affecting factors was performed by the central composite experimental design (CCD) and response surface methodology. It was found the average particle size of CMP wastewater was smaller than 100 nm. This characteristic made it was not easy to obtain high removal efficiency of suspended solids (SS) and turbidity when the CMP wastewater was treated by nano-bubble flotation without addition of any chemicals. The results of FFD experimental showed that activators (Al2(SO4)3 and FeCl3) and recycle ratio had significant effects on removal of SS and turbidity except pH and collectors (NaOH and CTAB (n-cetyltrimethyl ammonium bromide)). After the evaluation of results of CCD, response surface and quality of treated water, the optimized conditions for SS (>99%) and turbidity (>95%) removal were found to be 285 mg/l Al2(SO4)3 and 5 mg/l CTAB, respectively. Overall, the nano-bubble flotation showed high potential for treatment and reclamation of CMP wastewater produced from semiconductor manufacturing.