Comparative study of ionic contamination in cleanroom wipers using capillary ion analysis (CIA)

Several experimental approaches have been considered to address the problem of detecting and quantifying the ionic contamination in semiconductor cleanroom consumables such as wipers. A relatively new analytical technique called capillary ion analysis (CIA) appeared to us as an outstanding and convenient tool for the separation and quantification of both cationic and anionic species present in cleanroom wipers. Multiple wipers were used for extraction in high-purity deionized water to derive better sampling averages, as well as to enhance the levels of ions in solution. The resulting extract solution was preconcentrated by evaporation to further increase the signals from the released ionic species. The instrumental capability was checked by estimating the limits of detection (LOD), as well as, limits of quantification (LOQ). For cations, LODs were as low as 0.05 mu g/mL or 50 ppb; while for the anions, LODs were 0.1 mu g/mL or 100 ppb. A recovery study was conducted to determine the efficiency of the technique for ion removal from wipers. The study was also done to prove that for the detection of extremely low levels of ionic contamination, fluorinated plasticware is preferable over glassware to avoid risk of sodium contamination.