Issues of wet cleaning in ULSI process

Wet cleaning in actual LSI process is difficult to remove contamination perfectly, because the cleaning condition must be moderate to maintain device characteristics and device texture and because wet cleaning is not so effective for the particles generated during processes such as etching, photo lithography and film formation. Particle reduction depends on particle characteristics, i.e. the sticking force and the chemical structure of the particles. Metallic contamination on wafers, depending on the kind of solutions and the metal concentration in cleaning solutions, degrades TDDB characteristics and recombination lifetime. Although the lifetime degradation by the metallic contamination is appreciable, it is much smaller than those caused by damage in etching and in ion implantation.