A Study on Reclaimed Photoresist Developer Using an Electrodialysis Method

Photoresist developer reclamation technology and systems have been investigated and characteristics of the reclaimed developer were evaluated. High-purity tetramethylammonium hydroxide (TMAH) aqueous solution adjusted to an appropriate concentration is generally used as the photoresist developer in the lithography step for large scale integration (LSI) and liquid crystal display (LCD) manufacturing processes. TMAH was recovered by an electrodialysis (ED) method from developer waste (spent developer), and purified by ion exchange (IE) technologies. The reclaimed developer was analyzed and found to feature the same purity as fresh commercial developer and no differences in their characteristics as developer material could be determined. Our experimental reclamation system recovered more than 80% of stable TMAH from waste and, moreover, achieved large reductions in operating costs, which amounted to total cost reductions of 55–75% for LSI and 65–85% for LCD compared with the conventional systems without reclamation studied by us. In addition, environmental load was reduced.