Surface pretreatment and passivation utilizing high concetrated HCL and NH4F solution for germanium-based technology

In this paper, an interface treatment for (100) Ge using HCl cleaning with different concentration and passivation with HCl and NH₄F is experimentally demonstrated. The root mean square roughness (Rms) of Ge surface is reduced from 1.95nm to 0.274nm by 36% HCl cleaning, due to the high efficiency to remove the sub-oxide on Ge surface. After the pre-cleaning process, passivation with 10% NH₄F achieves a stable surface by suppressing the re-oxidation of Ge surface. Ge MOS capacitors using HCl cleaning and NH₄F passivation method exhibits better C-V performance with the hump disappearance and less frequency dispersion.