ISSUES OF WET CLEANING IN ULSI PROCESS

Wet cleaning in actual LSI process is difficult to remove contaminatio n perfectly, because the cleaning condition must be moderate to mainta in 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 d epends on particle characteristics, i.e. the sticking force and the ch emical structure of the particles. Metallic contamination on wafers, d epending on the kind of solutions and the metal concentration in clean ing solutions, degrades TDDB characteristics and recombination lifetim e. 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.