Angled XPS analysis of low-k dielectric surfaces after cleaning

Abstract

The N2/H2 plasma treatment is relatively poor in removing CuF2 contaminants and oxidized carbon contaminants on the dielectric sidewalls in comparison to other cleaning methods. Stripper A is very effective in removing any CuF2 contaminants on Cu surface both at the trench bottoms and dielectric sidewalls. However, stripper A causes carbon contaminants on the dielectric sidewalls to increase. Stripper B has a similar effectiveness as stripper A in removing carbon contaminants, but it is half as effective as stripper A in removing Cu, O, F contaminants. A two-step cleaning process that uses H/H2 plasma treatment followed by wet cleaning helps to improve contaminant removal. N2/H2 plasma treatment followed by DHF cleaning removes the largest amount of Cu(2+) contaminants from both the trench bottoms and dielectric sidewalls, especially CuO. N2/H2 plasma treatment followed by stripper A has been shown to be the best cleaning process among all the various cleaning methods evaluated here.