Particle Removal Efficiency Evaluation at 40 nm Using Haze Particle Standard

摘要

Haze particle standard has been developed using a novel particle deposition technique. PSL spheres and tungsten particles are used to prepare the standard wafer. Monodisperse test particles of 41 nm and 64 nm are deposited on bare silicon wafer as spots and they are detected using the scanner's haze mapping capability. Haze calibration curves were obtained by correlating the measured haze with the defect density. As a consequence of the haze standard development, a technique has been developed to determine the particle removal efficiency measurement of wafer cleaning system below the lower detection limit of wafer scanner. Particle removal efficiency of two wafer cleaning processes - a wet-chemical spray clean and a CryoKinetic clean - was measured using the haze particle standard, for particles of 41 nm size. The effects of defect density, particle size and material, surface roughness on the particle removal efficiency were characterized as part of the analysis. For wet cleans, removal efficiency was found to be as high as 98%. For CryoKinetic cleans, it was found to be 94.3%.