| This thesis addresses the issue of passivation film damage during focused ion beam IC modification. Patterned wafers with both PSG and silicon nitride as the passivation film were examined using focused ion beam technology to characterize one common damage mechanism associated with the passivation film and to study the factors which determine the failure incidence. The influence of specimen temperature, ion flux, traverse velocity, and ion energy on the occurrence of passivation film failure events was investigated. It is proposed that liquid gallium condensation inside pre-existing pores results in short-circuiting of surface charge to underlying, grounded aluminum metallization lines. The surface diffusion of Ga+ ions to and along the defects controls the kinetics of the observed failure events. The activation energy of the failure process was determined to be 0.26 eV. The results suggest that focused ion beam causes passivation film damage only if defects pre-exist in the film. Therefore, the focused ion beam method can be a powerful defect-finding tool for checking the quality of both the passivation film and dielectrics in general. |
