The phenomenon and mechanism of germanium (hereinafter Ge) dissolution in sulfuric acid based solutions were studied. The sulfuric acid concentration, the presence of an oxidizer and the treatment time were varied as parameters of these tests. It was clarified that Ge surface is covered by two layers: germanium dioxide (hereinafter GeO2) and germanium monoxide (hereinafter GeO). GeO2 dissolves easily in water and in the sulfuric acid solutions with high water fraction. On the other hand, the dissolution of GeO and Ge is influenced strongly by the sulfuric acid concentration in the solution and the treatment time when oxidizer is present in the solution.

Ultrapure water contains dilute hydrogen peroxide as an impurity. In order to clarify an impact of the dilute hydrogen peroxide on cleaning processes, a SiGe epitaxial layer was deposited on a Si(100) wafer which surface was treated by HF last process with hydrogen peroxide contained UPW or hydrogen peroxide removed UPW. The defect in the SiGe epitaxial layer was reduced when the hydrogen peroxide removed UPW was used.

The introduction of Co into MOL and BEOL requires a robust wet clean, especially the optimization of the Co rinsing step seems to be critical. The wafer rinsing solutions with a precisely controlled pH and oxidizing additive have been developed to suppress the Co corrosion. In addition, the mechanism of passivation and corrosion of the cobalt surface as well as the passivation stability is discussed.