Sputtering of amorphous silicon nitride irradiated with energetic C 60 ions: Preferential sputtering and synergy effect between electronic and collisional sputtering

Amorphous silicon nitride films (thickness 30nm) deposited on Si(001) were irradiated with 30–1080keV C60 and 100MeV Xe ions to fluences ranging from 2×1011 to 1×1014ions/cm2. The composition depth profiles of the irradiated samples were measured using high-resolution Rutherford backscattering spectrometry. The sputtering yields were estimated from the derived composition profiles. Pronounced preferential sputtering of nitrogen was observed in the electronic energy loss regime. In addition, a large synergy effect between the electronic and collisional sputtering was also observed. The sputtering yields were calculated using the unified thermal spike model to understand the observed results. Although the calculated results reproduced the observed total sputtering yields with a lowered sublimation energy, the observed preferential sputtering of nitrogen could not be explained. The present results suggest an additional sputtering mechanism related to the electronic energy loss.