Removal of Contaminant Nanoparticles with $$\hbox {CO}_2$$ Nanobullets at Atmospheric Conditions

Abstract

As the feature size of semiconductor chips is decreasing down to nanometric scales, cleaning of nanoscale contaminant particles without damaging the fine features puts forth severe technological challenges. Here we introduce a design methodology of a nozzle to generate a beam of supersonic $$\hbox {CO}_2$$ solid nanobullets into the air at atmospheric pressure, which dislodge the contaminant particles by colliding with them. The dry cleaning scheme proposed here does not resort to the chillers, vacuum chamber, and carrier-gas handling system, which conventional dry cleaning systems often required and thus hampered their practical applications. We provide a theoretical framework to select key design parameters, such as the area ratio of the nozzle throat and exit and the supply gas pressure. We experimentally verify the superior capability of our nozzle in generating a $$\hbox {CO}_2$$ aerosol beam under the atmospheric back pressure condition. Additional process parameters including the stand-off distance and the incident angle of the $$\hbox {CO}_2$$ beam are optimized to maximize the cleaning efficiency and minimize the pattern damages. Our work suggests a practical nanoparticle cleaning scheme that is faster and simpler than the conventional dry cleaning methods.