A new technology in which ultrapure water only was electrolyzed non-chemically with low electric power (<100W) was introduced for EUV mask cleaning application. Electrolysis was carried out with cation and anion exchange membranes, producing electrolyzed cathode and anode waters of amphoteric characteristics. Electrolyzed cathode water was very stable chemically for a long period while electrolyzed anode water was very oxidative. Electrolyzed cathode water minimized the adsorbed residues of previous chemical treatments with minor surface modifications with high PRE(particle removal efficiency). Unlike cavitation effects of other water containing H2 gas, its PRE was significantly improved by increasing megasonic energy. In terms of ionic strength, electrolyzed ion waters were much closer to environmentally benign UPW than chemical water. As a result, it has recently been successfully adopted for all EUV mask cleaning as a POR(process of record) recipe clean by two top semiconductor memory chip manufacturers in Korea. While, electrolyzed anode water is now under further study in terms of molecular dynamic behavior with some promising results of applicability because it showed very optimized oxygen-free oxidative and amphoteric properties, which is essentially prerequisite for removing inorganic contaminants as well as organics while leaving no residue on EUV mask surface. Ions of H+ and OH- in electrolyzed cathode water and OH° radical in electrolyzed anode water seemed to take key roles for cleaning under hydrogen bonding circumstance of water molecules. It was concluded that electrolyzed ion waters should fulfill the technical requirements for EUV mask cleaning. Combined application of electrolyzed cathode water with electrolyzed anode water may even be the ultimate alternative for EUV mask cleaning.
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