Numerical Analysis on Performance of Different Ceiling Coverage of fan Filter Units in Semiconductor Fabs

Abstract

In practical semiconductor fabs engineering, in order to reduce the investment cost, low coverage rate of FFUs is usually adopted and the air supply velocity is high, which brings high resistance to the filter mounted at FFU’s outlet. If a higher ceiling coverage and lower air velocity speed are used, the resistance may be significantly reduced and remarkable energy saving benefits can be obtained. In this study, CFD technology was adopted to simulate airflow in a semiconductor fab and air circulation resistance was obtained by theoretical calculation. Four ceiling coverage of FFUs, 25%, 50%, 75%, 100%, were studied under the condition of same air volume. The particle concentrations and payback period were analysed. The results show that (1) with the increase of the coverage rate, the concentration in most areas decreases significantly while only a small increase in the local area around occupant, and the particle concentration still meets the requirement; (2) adopting high coverage rate for transformation, the initial investment of FFUs increases slightly and the operating cost decreases significantly, and the payback period is only 1.1-2.3 years when 25% coverage rate is transformed into 37.5% - 75%.