Ultrahigh resolution secondary ion mass spectrometry profiling with oblique O 2 + beams below 200 eV

Based on a model that formation of (near) full oxide slows down or eliminates development of surface topography in Si, we explored conditions under which an oblique O 2 + beam at a few hundred electron Volts does not stimulate significant surface roughening in Si in ultrahigh vacuum. It was found that bombardment of Si by an 158 eV/45° O 2 + beam achieved (near) full oxidation at the initial stage of sputtering erosion of Si and eliminated rapid onset of roughening as often observed for sub-keV oblique O 2 + beams. Thanks to the minimal surface roughening and atomic mixing in Si with the 158 eV/45° O 2 + beam, secondary ion mass spectrometry profiling with this beam provided an unprecedented high depth resolution in characterizing SiGe deltas in Si.