Wet Cleaning by Using Amphoteric Electrolyzed Water for Mask Cleaning

Abstract

Process achievement for manufacturing extreme ultraviolet(EUV) semiconductor device requires profound technical varieties such as extreme extension of the existing concepts or new evolutional ones. In this study, a new technology was proposed to fulfill technical details required for EUV semiconductor device cleaning and manufacturing. The special electrolysis technology of ultrapure water(UPW) was introduced to generate water possessing quite unexpectedly mixed character such as pH of 6.5 to 6.7 and oxidation reduction potential(ORP) of -540 to –560 mV at room temperature. Since ORP of –550 mV lasted for several days, it was postulated that water clustering reaction due to hydrogen bond could hinder or retard recombination of H+ and OH- ions by synchronously isolating them electronically and physically. This amphoteric water was applied to cleaning process of EUV device manufacturing to carry out the experiment requiring eventually no chemical use for wet cleaning because of 10 nm feature size. Some results were so excellent that it was convinced that this water clean was evolutional to meet EUV requirements. This water did eliminate adsorbed leftovers of previous chemical treatments and minimized surface modifications because of non-chemical character so that it did not provide any chance of haze formation. Since particle removal efficiency(PRE) was very high, it was proposed that there might be other cleaning mechanism than double layer repulsion(DLR) of colloids. Conclusively, it is time to review the conventional wet cleaning technology and to adopt new concept of the amphoteric water to realize the cleaning technology of EUV device era.