Smoothing of the Si surface using CF4/O2 down-flow etching

The investigation of the surface morphology changes for Si surfaces treated with CF4/O2 reveals that the rough Si surfaces can be smoothened and Si trench corners can be rounded using CF4/O2 down-flow etching. Down-flow discharged CF4/O2 gas mixture in high O2 concentration etches the Si surface on which the SiFxOy forms. Fluorine atoms are prevented from reacting with Si by the formation of a thick SiFxOy layer at the concave part of the surface.