Removal of surface contaminants by cryogenic aerosol jets

Abstract

Removal of surface contaminants by various cryogenic aerosol jets has been experimentally investigated. Simplified theoretical consideration of their removal mechanism has been also presented based on the impact power of the aerosol jets. Under atmospheric operation, water vapor and carbon dioxide could make their particles independent of their concentrations in the carrier gas while argon and nitrogen could hardly solidify to their own particles. The cryogenic aerosol jets were very effective in removing both submicron particle contaminants and photoresist films on wafers. The rate of the PR film removal strongly depended on the hardness of the film. Molecular organic films could be also removed with the aerosol jets. In general, the removal of the contaminants depends primarily on the physical impact. The removal rate increased with the mass concentration of the aerosol particles, regardless of their nature. The rate also increased with the impact velocity of the jets which was controlled by either the chamber pressure or the distance between the nozzle tip and the contaminant surface. The cryogenic aerosol-free jet was much less effective than the corresponding aerosol jets but had some effectiveness compared to the noncryogenic one. The thermal shock of the film was, therefore, supposed to have a secondary effect on the contaminant removal.