Evaluation of particles on a Si wafer before and after cleaning using a new laser particle counter

A new method has been developed to measure particle sizes of nanometer (nm) order on raw Si wafers by using a light-scattering method. Heretofore, we proposed a new measuring method that can theoretically detect a particle diameter of about 6 nm for particles on a raw Si wafer. A new apparatus measuring particle sizes was constructed according to the developed method. Then, it was verified that this measuring system could measure the particle size with a detection sensitivity of about 24nm. Particle detection on the surface of raw Si wafers was carried out with this measuring system; therefore it could detect a signal corresponding to a particle diameter of about 24~34 nm. Moreover washing of the Si wafer by the wet cleaning method was attempted to verify the measured signal as a particle. Consequently, it was verified that detected particles on the raw Si wafer are almost particles adhering on the Si wafer. Then it could be verified that the wet cleaning method is an effective method to remove particles of less than 0.1 μm diameter on a Si wafer surface