A Comparative Study on Velocity Fields, Humidity and Oxygen Concentration in a Front Opening Unified Pod (FOUP) During Purge

Microchip features continue to reduce in size year after year. Oxygen (O ₂ ) and moisture present in ambient air can cause product defects and therefore lower production yield. Smaller feature sizes are more sensitive to humidity and oxygen, resulting in a greater potential for defects to arise during wafer processing. Therefore, the level of oxygen and moisture needs to be minimized during integrated circuit (IC) manufacturing. Purge gases like clean dry air (CDA) or nitrogen (N ₂ ) are commonly used to reduce the level of oxygen and moisture inside a front opening unified pod (FOUP). In this study, purge cleaning performance was experimentally assessed by streamlines flow analysis, particle image velocimetry (PIV), relative humidity (RH) measurement, and oxygen concentration measurements during purging with practical flow rates of 130, 200 and 300 LPM. The experiments show 200 LPM can be the optimum purge flow rate for a high level of cleaning efficiency and a low level of vibration and instabilities. This purge flow rate can be used to increase product quality through a reduction in defect frequency, while reducing annual energy consumption by the semiconductor manufacturing industry.