Ammonia sorption outgassing and cross contamination ability of Entegris FOUPs evaluation and its volatile acids comparison

A comparative study was carried out to evaluate the capacity of two Entegris Front Opening Unified Pod (FOUP) polymers, PC and EBMCNT, to be contaminated by NH 3 , and the ability of these FOUPs to transfer ammonia to Cr-coated wafers. The results are compared to those previously published for molecular acids (HF and HCl) ranking the contaminant affinity to polymer as NH 3 < HCl < HF; and the ability to outgas is set as NH 3 > HCl > HF. The high outgassing ammonia concentrations are not directly related to a large contamination transfer to wafers since each phenomenon is predominantly governed by the solubility or diffusivity parameter respectively. This study has shown that EBMCNT FOUP is the best FOUP polymer tested. Finally, it was proven that PC FOUPs are not suitable in high ammonia environments because the polymer has a chemical reaction with the ammonia, causing it to degrade.