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Particles within plasma etching equipment stick to the wafer and cause defects, resulting in large scale integrated circuit (LSI) yield reduction. We observed the behavior of particles resuspended in a vacuum chamber using a laser light scattering method. Investigating the influences of gases, static electricity, and plasma on particle resuspension, we found out that particles are not only suspended by the shock wave or gas viscous force generated when the valve opens or when the gas is introduced into the chamber, but also are resuspended due to electromagnetic stress caused by electrostatic chuck voltage application or radio frequency discharge. If, on the other hand, stable plasma generation is assured, particles are positively charged and receive repelling force within the ion sheath; as a consequence, particle resuspension is suppressed. We developed a method that can suppress particle resuspension by avoiding the production of a shock wave and electromagnetic stress during the wafer processes. We also developed a method that can effectively remove particles before the beginning of processes that use gas viscosity, the shock wave, and the electromagnetic stress.
Date of Publication: Nov. 2005