BEHAVIOR OF ULTRAFINE METALLIC PARTICLES ON SILICON-WAFER SURFACE

The diameter of particles which adversely affects the yield has been s hrinking as ULSI devices are more and more miniaturized. Ultrafine par ticles with diameters of 0.1 mu m or less have become important recent ly. Ultrafine particles of this type are expected to be difficult to r emove. This study has established a method to evaluate ultrafine parti cle removal efficiency. Ultrafine metallic particles with diameters of several to several hundreds of nanometers were deposited on the Si su rface using a gas deposition method. The removal efficiency of the ult rafine particles using various cleaning solutions was investigated. AP M (NH4OH-H2O2-H2O) cleaning can remove 150 nm Au particles, but cannot remove ultrafine Au particles with a diameter less than several tens of nanometers. In addition, the Si surface becomes rougher when a DHF- H2O2 cleaning is performed to remove Au ultrafine particles. This is b elieved to be because noble metals such as Au, Ag, and Cu, which featu re a higher electronegativity than Si, attract electrons from Si facil itating Si oxidation.