Treatment of Wastewater Containing H2O2 in Semiconductor Fabrication by Catalase Dosing

• Main Authors: Wu, Min-Hsueh, 吳旻學
• Other Authors: Huang, Chihpin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/49635615822618467117

碩士 === 國立交通大學 === 工學院永續環境科技學程 === 102 === Among the processes for manufacturing semiconductors, the circuit multiproject CMP and wet-etching processes involve using a considerable amount of ultrapure water for cleansing wafers. During the cleansing and etching process, FPM、SPM、HPM and APM present in Radio Corporation of America (RCA) cleaning solutions, both contain H2O2. The grinding fluid used in the copper-containing (Cu-CMP) also contains H2O2. Of the aforementioned processes, the waste water produced during Cu-CMP is the most difficult to recycle because this water contains several grinding fluids, including numerous nanoparticles, surfactants, and H2O2. Currently, the industrial field has mostly adopted chemical coagulation for water treatment. However, when the concentration of H2O2 in the water is excessively high, the floc in the precipitation tank easily floats upward, thereby influencing the quality of the recycled water. If the H2O2 in waste water can be removed in advance to stabilize the inflow concentration of coagulants, the quality and quantity of recycled waste water can be substantially improved, effectively enhancing the recycle rates of an entire water treatment plant. In this study, catalase was used because it can dissociate H2O2 into water and oxygen. A jar test method designed to be combined with various reaction conditions was employed to determine the limitations of catalase addition and identify the optimal iv amount to be added. The results showed that the pH value, temperature, and reactive substrate concentration in water affected the catalase reactions and H2O2 removal rates. The experimental results revealed that water temperatures below 35°C and at pH 5 and pH 9 exerted minimal influence on removal rates. In the electrical conductivity experiment of the water body, the results showed that the reaction and removal rates after 20 min of reaction at a conductivity of 5000 μS/cm and 20000 μS/cm were 90.6% and 95.0%, respectively, yielding a difference of 4.6%. In addition, in the water quality sampling analysis, the two currents of waste water from CMP and Cu-CMP satisfied the optimal environmental conditions for catalase reactions. However, differing catalase reactivity generated considerable differences in H2O2 removal rates. When the amount of chemical added was identical, the H2O2 removal rates could engender a difference of 40%. Therefore, in addition to considering appropriate pH and temperature conditions, researchers must particularly monitor the activities of catalase and avoid using low-activity catalase, which may increase the amount of chemicals required during water treatment and thereby increase relevant expenditures.