Purging of foup for 450 mm wafer manufacturing

This study is designated to experimentally determine the effect of clean dry air (CDA) purging rate on purging efficiency in a beta version 450 mm PC FOUP, which fully loaded with 25 pieces of dummy wafers. The purging CDA with flow rate range of 30~180 L/min (LPM) were tested. The purging gas enters the FOUP through the two rear ports. For each case, a total purging time of 30 minutes was set to simulate the purging process once the mass flow controller was modulated to lead-in the purging gas. Cleanliness requirement of moisture content (RH ≤ 5%) within the FOUP was served as key evaluation factor. The results showed that higher purging rate of CDA demonstrate favorable moisture depletion rate within the gaps formed between the wafers. The middle area (wafer slot #13) was the place that the purge air difficult to reach to and no significant of improvement in purge time was observed for higher purge rates cases i.e. 150 LPM and 180 LPM cases.