Principles and mechanisms of sub-micrometer particle removal by CO2 cryogenic technique

The removal of sub-micrometer particles from surfaces is critical in different manufacturing processes requiring precision cleaning, such as in integrated devices, microsystems, read/write head, magnetic recording media, etc. Defects caused by small particles can adversely affect device performance and yields. The efficiency required in removing increasingly small particles without affecting underlying film integrity is a major challenge in standard wet cleaning. This paper describes the theory and mechanism of a dry, non-etching cleaning method in the form of CO2 cryogenic aerosol. A theoretical model of particle removal is presented along with discussions on the forces of particle-substrate adhesion in air. Results of cleaning experiments using standard polydisperse particles and slurries provide the validity of the cleaning model.