Alkaline cleaning of silicon wafers: additives for the prevention of metalcontamination

The paper presents a new strategy for cleaning of silicon wafers. A novel c lass of chelating agents added to alkaline cleaning mixtures provides promi sing performance without negative effects such as metal redeposition due to residual metal contamination of the cleaning solution. The superior capabi lity of the new cleaning process is confirmed by the results obtained from wafer surface metal analysis as well as from minority carrier lifetime and diffusion length measurements and gate oxide integrity tests. Particle dens ities and surface roughness are not influenced by the presence of the chela ting agents in the cleaning solution. TOF-SIMS measurements do not indicate any deposition of chelating agent on the wafer surface. With this type of modified SC-1 cleaning procedure the acid SC-2 step used in conventional RC A cleans to remove the metals deposited in the preceding SC-1 step is unnec essary resulting in substantial cost savings with respect to chemicals, was te, equipment and space. (C) 1999 Elsevier Science B.V. All rights reserved .