Performance of Different Front-Opening Unified Pod (FOUP) Moisture Removal Techniques With Local Exhaust Ventilation System

A highly effective moisture removal technique for front opening unified pods (FOUPs) can significantly improve the production yield of semiconductor manufacturing industries by minimizing the number of faulty dies rejected due to humidity related defects in silicon wafers. In this study, FOUP purging using clean dry air (CDA) was applied using conventional and diffuser purge method. An innovative laminar air curtain was also used to increase the performance of the FOUP purging techniques. These moisture removal techniques were applied in an open FOUP connected to a mini-environment in which a local exhaust ventilation (LEV) was installed. A novel smoke flow visualization technique and particle image velocimetry (PIV) were employed to visualize the flow pattern inside the FOUP and to generate a velocity vector field from the flow field. In addition, digital humidity sensors were installed inside the FOUP to evaluate the performance of the techniques. The flow analysis and humidity data show that the air curtain can significantly improve the performance of the purge methods. The observations demonstrate that the application of the air curtain, in combination with diffuser purge, can significantly improve the FOUP cleanliness. The LEV system was not found to have influence on the flow field inside the FOUP.