A Numerical Study on the Effects of Purge and Air Curtain Flow Rates on Humidity Invasion Into a Front Opening Unified Pod (FOUP)

Minimizing airborne molecular contamination (AMC) and moisture significantly decreases the defect rate of semiconductor products during manufacturing. Humid air originating from the fan filter unit (FFU) that is located at the top of a mini-environment (ME) might be transferred into a front opening unified pod (FOUP). Different moisture removal techniques such as diffuser purge and air curtain were applied to minimize the humidity level inside the FOUP. This computational fluid dynamics (CFD) numerical study evaluates the relative humidity (RH) level inside the FOUP subjected to different moisture removal techniques when the door is open. Different practical purge and air curtain flow rates were simulated. The large eddy simulation (LES) model was performed to simulate eddies inside the FOUP and ME. The relative humidity contours were also simulated inside the FOUP and ME. The results of the simulations were verified by experimental RH measurements. The findings show that combining the methods of diffuser purge and air curtain with flow rates of 130 and 360 LPM respectively has the highest moisture removal efficiency. This method can significantly decrease the humidity level inside the FOUP, resulting in a decrease in the defect rate on silicon wafers during manufacturing and storage.