APM and AES studies on the electron-beam-irradiation-induced modificationsin superficial and buried SiO2 layers

The interactions between electrons and SiO2 are of interest to modern mater ials characterization and processing technologies. In this work, electron-b eam-irradiation-induced modification has been investigated in a superficial oxide (SiO2/Si) and a buried oxide in Cu/TaN/SiO2/Si using atomic force mi croscopy (AFM) and Anger electron spectroscopy (AES), In the superficial ox ide layer, a hole of 15 nm deep and 2.5 mu m wide was observed, after the o xide had been irradiated by a 20 keV 50 nA electron beam rastering over 1.5 x 1.5 mu m(2) for 30 min. In the buried layer, however, bumps of 40-90 nm high and similar to 10 mu m wide were generated after irradiation of a 20 k eV 150 nA electron beam rastering over 1.5 x 1.5 mu m(2) for 5-40 min. Surr ounding the hole and the bumps were halo-like features, In the bumps, small holes were visible, The observations have been explained by proposing a mo del whereby, upon irradiation by electron beams, both the swelling and the loss occur in the SiO2 layer, The swelling happened as a result of the gene ration of voids inside the irradiated volume, whereas the loss was attribut ed to the desorption of O-2 formed by the oxygen atoms originally dwelling at the surface and those diffused to the surface, It is suggested that the TaN barrier layer, which prevented oxygen diffusion from the oxide, played a prominent role in the swelling of the buried SiO2, The damage to SiO2 was demonstrated further with Auger depth profiling analyses, and the correspo nding artefact appearing in the analysis was discussed. Copyright (C) 2000 John Wiley & Sons, Ltd.