Reduction of Surface Roughness in Epitaxially Grown Germanium by Controlled Thermal Oxidation

Obtaining a smooth substrate with surface roughness of 2 Å is essential for semiconductor device fabrication. In this letter, we characterize the effect of thermal oxidation of epitaxially grown Ge on its surface roughness. First, the effect of oxidation on root-mean-square roughness is investigated for epi-Ge surface that is bombarded with phosphorous ions. Next, the effect of oxidation is investigated with the presence of low thermal oxide layer on the epi-Ge. Finally, examination of the effect of temperature on surface roughness for capped epi-Ge is conducted. By making the Ge oxidation diffusion limited, surface roughness can be reduced to ~2 Å.