Improvement of photoresist removal efficiency in ozonated water cleaning system

Ozonated water cleaning systems are used to remove photoresist and organic contaminants on silicon wafers and natural organic matter and bacteria in drinking water. In this paper, the effects of O3 concentration, the system of ozonated water vapor, and substrate temperature on the removal efficiency of photoresist were investigated. A 11.59 kcal/mol of activation energy was obtained for the reaction between aqueous O3 and I-line photoresist. Increasing the process temperature increases the reaction rate of aqueous O3 and photoresist, but reduces the solubility of O3 in water for O3-injected system. Therefore, it is important to deliver aqueous O3 to the wafer surface effectively. The removal rate of photoresist has been accelerated by controlling formation of a boundary layer as well as the temperature of the ozonated water and O3 solubility. When water vapor was generated with O3 and sprayed through a nozzle, the highest removal rate of photoresist, 221 nm/min, was obtained. From the results observed in this study, it is concluded that it is important to have a fast uniform boundary layer formation, a thin boundary layer, and production of high concentrations of O3 in the chamber in order to improve the removal efficiency of photoresist in the ozonated water system.