Metal adsorbent for alkaline etching aqua solutions of Si wafer

High performance adsorbent is expected to be synthesized for the removal of Ni and Cu ions from strong alkaline solution used in the surface etching process of Si wafer. Fibrous adsorbent was synthesized by radiation-induce emulsion graft polymerization onto polyethylene nonwoven fabric and subsequent amination. The reaction condition was optimized using 30 L reaction vessel and nonwoven fabric, 0.3 m width and 18 m long. The resulting fibrous adsorbent was evaluated by 48 wt% NaOH and KOH contaminated with Ni and Cu ions, respectively. The concentration levels of Ni and Cu ions was reduced to less than 1 μg/kg (ppb) at the flow rate of 10 h−1 in space velocity. The life of adsorbent was 30 times higher than that of the commercialized resin. This novel adsorbent was commercialized as METOLATE® since the ability of adsorption is remarkably higher than that of commercial resin used practically in Si wafer processing.

► Adsorbent was synthesized by radiation-induced emulsion graft polymerization.
► Degree of grafting reached 120% at the pre-irradiation of 50 kGy.
► The resulting adsorbent removed Ni and Cu ion in strong alkaline solution.
► Adsorbent was commercialized for filter of Si wafer etchant.