While modern ultrapure water (UPW) systems are relatively well developed for semiconductor manufacturing, there is still room for improvement with regards to enhanced reliability, reduced environmental impact, and cost reductions. Membrane distillation (MD) is one promising alternative for high-purity water production that has several advantages compared to reverse osmosis (RO) and other technologies. In short, MD is a thermally driven process utilizing a hydrophobic membrane to produce high-purity water from a contaminated feedstock. Previous studies have shown that MD produces water with equal or superior quality to RO; in addition MD is relatively insensitive to process variations (e.g. pH, TDS levels, etc.), thus opening up the possibility of recycling rinse water. Low-temperature heat sources (i.e. under 100 °C) may be employed, thus allowing MD to be readily integrated into existing processes or even on-site cogeneration.
This paper explores the viability of MD for high-purity water production in a typical semiconductor chip fabrication plant. A brief literature review is included along with water quality analysis reports on typical MD product water. System simulations are employed to highlight possible scenarios with cogeneration. Results show that the specific energy consumption in the case study is around 440 kWh/m3 (thermal) and 0.9 kWh/m3 (electrical). The specific capital cost is around $1.2-1.5/ m3 for the MD facility. These findings provide a strong impetus towards demonstration trials and other follow-on research and development activities.
2006. Vol. April