Waste water management in TSMC, Taiwan
Making good use of water resource is of paramount importance for any industry. Taiwan Semiconductor Manufacturing Company (TSMC), the world leading wafer foundry, began to work on waste water recycling in 1995, and has developed a brand new waste water recycling system. The rate of recycled waste water can now reach nearly 90%, which is an unmatched level.
According to a climate study by Research Center for Environmental Changes, Academia Sinica, Taiwan in 2011, Taiwan's rainfall situations becomes increasingly polarized, in that rainfall occurs less frequently in the dry season but more in the wet season. Although the average amount of rainfall in Taiwan reaches 2,500 mm, which is 2.6 times the amount of the global average, but 70% of the rainfall has flown into the ocean. The actual available and usable amount accounts for 26% of the annual rainfall amount. Taiwan has been decreed as the 18th country suffering from water shortage.
In this context, TSMC has committed to making efforts in order to reduce its huge water consumption. To achieve this task, TSMC has developed new technologies towards recycling waste water. Instead of being satisfied with meeting the minimum standard of water and wastewater treatment, TSMC has kept taking proactive measures for a promising future. Moreover, as TSMC is committed in carrying out a Corporate Social Responsibility approach, the company has no choice but to take into account the waste water treatment.
TSMC’s major water-consuming process consists in cleaning chemical residue on wafer surfaces through an ultra-pure water system. The strategic planning is a three-step approach based on (i) controlling water pollution by reducing pollutants, (ii) recycling these pollutants and (iii) recovering these pollutants. In order to reduce the global water consumption, the effluent water from ultra-pure water systems and process tools are rated (depending on their purity), using a strict classification. The purest water is reused in the production scheduling process whereas the poorest grade goes to secondary uses (human contact is avoided) such as water for cooling towers and wet scrubbers, cleaning water for sludge dewatering filters, and toilet water. Wastewater that cannot be recycled is discharged to treatment facilities for final wastewater treatment.
Why did it work?
The wastewater under the chemical separation and physical separation can be split into fluoride, copper, general acid, and various polishing wastewaters. Every type of wastewater is strictly classified at process tools, and directed to wastewater treatment facilities through distinct piping devices. More than 20 categories of drainage types are used, carefully operated and maintained to meet the standards of the Science Park Administration.
Also, TSMC works in partnership with industries and universities to improve discharge quality in fields like Chemical Oxygen Demand (COD), Tetra-methyl ammonium hydroxide (TMAH) and NH3-N reduction in order to reduce hazards towards water bodies. As a result, it has led to 62.5% of the COD discharge reduction in 12-inch fabs.
Based on an internal study in TSMC in 2013, the entire recycling rate of process water accounted for 86.5% in 2012, which also economically generated 40 million EUROs profit and attested the invlovment of TSMC in water savings.
As a renowned international company, TSMC has not adopted a minimum process water recycling rate of 85% but has also selected low water consumption process tools, implemented process water drainage segregation, set up processes with reclaimed water systems in several new factories, and has continued promoting water saving measures for mass production. The purpose of such an approach is to reduce the fresh water demand.
TSMC’s overarching goal is to be a leading global company in water resource management. This objective is based on water savings in daily operations and on implementing the developed separating measures in the supply chain. Based on its achievement so far, its maturity is estimated to be 9 on TRL scale.