Identification and cleaning effect of active intermediates in the O3/ultraviolet ray/supersonic wave multiple reaction using a low-temperature sprayed TiO2 photocatalyst
Sustain. Environ. Res., 25(6), 323-329 (2015)
Seiichi Ishikawa, Sen Li, Chen Huang, Teiji Tanizaki, Wenhao Zhang, Tomohiko Higuchi and Hisato Haraga
Ozone, nano-reaction field separation type of TiO2 photocatalyst, ultraviolet ray irradiation, supersonic wave irradiation, OH radicals
Water for cleaning wafers intended for integrated circuit (IC) fabrication was produced using a combination of ozone (O3), ultra-violet ray (UVR), super-sonic wave (SSW) and a TiO2 photocatalyst deposited on quartz glass by low-temperature spraying. Using both UVR and SSW led to a decrease in the concentration of oxidants in the treated water compared to the case for UVR alone. However, the oxidant concentration increased in the presence of the photocatalyst. Although the O3 concentration was reduced by SSW irradiation, in the presence of the photocatalyst over half of the oxidants were species other than O3. Following UVR, no O3 was detected and only a small amount of other oxidants was present. Using both SSW and UVR irradiation led to an increase in the concentration of other oxidants. The concentration was further increased in the presence of the photocatalyst. Following SSW and UVR irradiation, the oxidants continued to exist for 5 min. The results of a chemiluminescense analysis indicated that the treated water contained mainly OH radicals associated with the ionization of metals. This water is expected to be effective for cleaning wafers prior to IC fabrication, in addition to other applications.