Removal of submicrometer particles from silicon wafer surfaces using HF-based cleaning mixtures

We have studied the particle removal efficiency of HF-based cleaning mixtur es used to clean wafer surfaces during semiconductor manufacturing. SiO2, S i3N4, and metallic oxide (Al2O3, TiO2) particles can be easily removed from silicon wafers using a HF-based clean, whereas the removal of metallic par ticles and especially Si and polymeric particles is much more difficult. Th is is explained in terms of surface hydrophobicity effects. For thermal oxi de wafer substrates, a low removal efficiency is observed for the positivel y charged Si3N4 and Al2O3 particles. This has been explained previously by redeposition of the particles from the carry-over layer during the final ri nse [R. Vos, I. Cornelissen, M. Meuris, P. Mertens, and M. Heyns, in Cleani ng Technology in Semiconductor Device Manufacturing VI, J. Ruzyllo, T. Hatt ori, and R. E. Novak, Editors, PV 99-36, p. 461, The Electrochemical Societ y Proceedings Series, Pennington, NJ (1999)]. Surfactants are found to incr ease the removal of Si and polymeric particles from silicon substrates. Thi s is attributed to the elimination of hydrophobic attraction forces. In add ition, the surfactant is also successful in preventing the particles from r edepositing during the final rinse treatment, because during the rinse, bot h the particle and the substrate have the same surface charge. (C) 2001 The Electrochemical Society.