Roughening of silicon (1 0 0) surface during low energy Cs+ ion bombardment

Nowadays, the use of low energy ion bombardment in secondary ion mass spectrometry (SIMS) is a mandatory step to obtain high depth resolution for the characterization of ultra shallow junctions. However, increment of roughness during ion bombardment leads to the degradation of depth resolution. The evolution of surface roughening and ripple formation on silicon at ambient temperature under 1 keV Cs+ ion bombardment with and without sample rotation has been studied by means of atomic force microscopy. Ripple formation with a perpendicular orientation with respect to the Cs+ beam direction has been detected, and their wavelength and correlation length have been monitored as a function of the experimental conditions. Roughness and wavelength increased with increasing ion fluence, while variations of ion flux showed little effect. The effect of sample rotation during ion bombardment led to a critical reduction of the surface roughness and disappearance of ripples.