Removing Spherical Silica Particles from Si, Ge and NiP Substrates by KrF Excimer Laser

Abstract

Particle adhesion and removal are of great interest in IC process and high-density hard disk manufacturing. Increasing effort is required to remove submicron particles. We investigated the adhesion and removal of spherical silica particles from silicon (Si), germanium (Ge) and NiP substrates using a KrF excimer laser. Atomic force microscope (AFM) point-contact mode measurement showed that the tip adhesion force on Ge surface is greater than that on Si or NiP surface, and the Hamaker constant of NiP is about 2/3 of that of Ge substrate. The cleaning efficiency and cleaning thresholds for standard-size particles with a diameter of 1.0 µm were measured. The cleaning efficiency was sensitive to laser fluence. The threshold laser fluences for Si, Ge and NiP are 100, 30 and 8 mJ/cm2, respectively. The different cleaning curves are not only due to the difference in adhesion on the substrates, but also due to the different optical and thermal properties of the substrates.