Germanium electrochemical study and its CMP application

When the feature size of ultra-large scale integrated(ULSI) circuit shrinks to sub-10 nm, germanium(Ge) as a novel material with high hole mobility is needed for further development. Chemical mechanical polishing(CMP) is an important process for the integration of channel materials into silicon wafer. In this paper, starting with electrochemical studies of Ge, different types and concentrations of oxidants for Ge corrosion were investigated; then the effect of NaCl and Dodecylamine for Ge activation and inhibition were studied. After that, corresponding CMP experiments were conducted, which confirmed the results of electrochemical experiments. Moreover the polish selectivity of Ge/SiO2 in H2O2-based slurry was also investigated. Atomic force microscope(AFM) was used to test the surface morphology of wafers after polish. Finally the slurry with 5 wt% SiO2 abrasive and 1 vol.% H2O2 at pH 9 were chosen to polish Ge/SiO2 wafers, and it has a high polish selectivity of Ge to SiO2 while high Ge removal rate and good quality surface were obtained.