半導體化學機械研磨廢水之處理與回收

Treatment of Chemical Mechanical Polishing Wastewater from Semiconductor Fabrication for Reuse

楊宗儒(Chung R. Yang)

指導教授 ： 林勝雄

元智大學/工程學院/化學工程與材料科學學系/碩士(2001年)

摘要

化學機械研磨(Chemical Mechanical Polishing, CMP)技術的開發是促使積體電路微小化的重要里程碑。但由於此項技術使用頻繁且乃屬於高污染的製程，所以需要大量水來進行晶圓清洗動作，相對所排放出的廢水量也很可觀。因廢水中含有許多擁有高介達電位(Zeta Potential)的微粒及在排放水標準以上的化學需氧量(Chemical Oxygen Demand,簡稱COD)值，本研究則利用化學混凝、逆滲透裝置、及臭氧捲氣設備，對實廠的化學機械研磨廢水進行處理。並以離子交換樹脂對銅製程CMP廢水進行處理。
本實驗以各類混凝劑(硫酸鋁、三氯化鐵、多元氯化鋁)進行化學混凝，探討各變因對處理效果的影響。由結果可知，各種混凝劑加藥量在特定的濃度範圍下，去除濁度能力都可達到10濁度單位(Nephelometric Turbidity Unit)NTU以下，當在適當濃度範圍外時反而會使濁度變更差。同時，pH值的配合，可以使加藥量減少，達到低濁度的目的。
利用臭氧破壞有機物是種去除水中COD有效方法，不過往往都因臭氧利用率低而使臭氧白白損失，於是本實驗利用了捲氣式反應器來提升氣體反應效率，且對於一些變因做了探討。可發現廢水COD去除率會因臭氧進入濃度增加而提高；控制葉片轉數達1200 rpm以上時，液面所產生的漩渦可以讓臭氧利用率提高；要處理的廢水在高pH值下才會有較佳COD去除率；加入活性碳纖維時不但有吸附能力同時也兼具催化效用。
在先進的廢水處理、食品、藥品工業及化學工業等，逆滲透被當作是種有效、經濟的分離程序，所以本實驗就採用了捲筒式的掃流逆滲透模組去除廢水中的COD。從實驗得知驅動壓力的增加不只可使透過量增加，還可讓過濾的效果達到更好；廢水溫度的上升有助於透過量增加，對於水的回收再利用率提高。濃縮液部分則再經由臭氧破壞，可有效的減少排放量。
在動力學方面，本實驗使用三種動力模式(指數、總和、及通式動力學模式)，來模擬臭氧質量流率變化、葉片轉數變化及廢水pH值改變時，COD的去除情形，發現在使用通式動力學模式是最符合臭氧的氧化反應情況。
半導體廠銅製程之CMP廢水其含銅離子的濃度一般不高，因此利用離子交換法吸附銅離子較為經濟，且可讓銅離子含量達到排放標準以下。在批次等溫吸附實驗中，修正型Langmuir及Freundlich能適切的描述其平衡現象，在連續式貫穿實驗中以Richards能適切模擬貫穿吸附情況，並由實驗結果得知Ambersep132此種樹脂的再生效果是不錯的。

關鍵字

化學機械研磨 ； 化學混凝 ； 臭氧 ； 逆滲透 ； 離子交換 ； 再利用

並列摘要

Chemical mechanical polishing (CMP) is an important step in the semiconductor fabrication. In the CMP process, a large amount of ultrapure water is employed to clean the wafer surface. Hence the CMP wastewater often contains considerable amount of fine oxide particles and some organic and inorganic compounds. In the present research, various chemical and physical methods, including chemical coagulation, reverse osmosis and gas-induced ozonation, were used to treat the CMP wastewater with an aim to recovering treated wastewater for possible reuse.
In the chemical coagulation, different coagulants, such as Al2(SO4) 3, FeCl3 and PAC/polymer were used. The effectiveness of these coagulants in removing the fine oxide particles were experimentally tested and the optimum operating conditions identified. Experimental results indicated that with proper dosage and pH control, all coagulants were effective in reducing the wastewater turbidity (in terms of Nephelometric turbidity unit or NTU). Among these coagulants, PAC/polymer combination was found to be the mosty effective and thus is recommended for practical purposes.
Destruction of organic compounds by ozone has been known to be an effective method. However , ozone utilization was generally poor in a conventional sparged reactor. In order to improve the ozone usage, gas-induced reactor was used in this study. It is found that the pollutant removal rate was much improved using the present reactor system. The test runs also revealed that when the impeller speed exceeds 1200 rpm, good vortex was formed in the reactor, leading to improved ozone utilization. Good COD removal was obtained particularly at high initial wastewater pH.
Reverse osmosis (RO) has been a popular process, widely adopted for wastewater treatment, food processing and chemical separation. In the present study, the spiral wound RO modules were employed to remove COD in the CMP wastewater. The test results showed that an increase in the operating pressure significantly enhances system permeation and solute rejection. Higher operating wastewater temperature was found to be beneficial to system permeation also. The overall COD removal by the RO process was found to be excellent and the permeate obtained from the RO system could be recycled for reuse.
The experimental COD removal data were employed to model the kinetic aspects of the oxidation process. Three kinetic models including exponential, lumped and generalized kinetic equations, were used to investigate the effects of mass flow rate, impeller speed, pH value of on the wastewater COD removal. The generalized kinetic model was found to be the best one among the three models in representing the ozone oxidation process.
Preliminary experimental tests were also conducted to treat the copper CMP wastewater. This wastewater was special in that it had a high copper concentration. Hence in the treatment process, copper removal became a major concern. In the present work, ion exchange process was adopted for copper recovery from the wastewater. Test runs were performed to collect data for determination of the copper removal efficiency and for modeling the equilibrium ion exchange process. Batch equilibrium test results revealed that the extended Langmuir and Freundlich isotherms describe well the equilibrium ion exchange process. In the column experimental tests, the breakthrough curves were found to be adequately modeled by the Richards equation.

並列關鍵字

Chemical Mechanical Polishing ； CMP ； chemical coagulation ； ozone ； Reverse osmosis ； ion exchange ； reuse

參考文獻

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