A case study on energy saving of the facility systems for 12-inch semiconductor wafer fabs in Taiwan

In recent years, the semiconductor wafer fabs have begun to produce 12-inch wafers instead of 8-inch wafers as the new generation process technology has evolved. The production area increases, and the energy consumption of production buildings is also increased. In a semiconductor fab, besides the processing equipments, the plant facility system consumes most of energy. The facility system contains chilled water systems, outside air supply systems, circulating air systems, exhaust-gas treatment systems, vacuum systems, process cooling water systems, ultra-pure water systems and compressed-air systems. Considering the gradual depletion of energy sources and the soaring energy cost, energy saving has become an important project to high energy consumption semiconductor fabs. Therefore, this paper presents a case study on the energy saving of a clean air conditioning system and facility of 12-inch semiconductor fabs. The energy saving schemes contain four cases: (1) Case 1: The gas consumption of the organic substance processing system of direct firing type is compared with that of regenerative heat recovery type; (2) Case 2: The energy consumption of the cooling tower adopting high and low speed operations is compared with that adopting a frequency converter; (3) Case 3: The low vacuum system of the clean room adopts the phone call system to switch on/off the pump, and (4) Case 4: The make up air unit of the clean room adopts the run around system to recover heat. As for the energy saving efficiency, Case 1 can save NT$9,881,616 of gas cost annually; Case 2 can save NT$2,398,913 annually; Case 3 can save NT$317,004 annually, and Case 4 can save NT$1,738,758 annually. Through the aforementioned four manipulations, 25.24% of the total energy consumption of the corresponding facilities can be saved.   Key words: Semiconductor fab, energy consumption, energy saving.