IMPLANTED GALLIUM ION CONCENTRATIONS OF FOCUSED-ION-BEAM PREPARED CROSS-SECTIONS

A gallium (Ga) focused-ion-beam (FIB) has been popularly used to prepa re cross-sectional samples for transmission electron microscopes (TEMs ) and scanning electron or ion microscopes. However, characteristics o f the FIB-prepared cross sections such as ion concentration and radiat ion damage have been little studied either in theory or in experiment. In the present study, cross sections prepared by 30 keV Ga FIB are mo deled using a combination of analytical and Monte Carlo methods to cal culate the implanted Ga concentration. It is found that the Si/W layer ed sample is cross sectioned at grazing angles beta approximate to 2.5 degrees and 6 degrees for these layers, respectively. The implanted G a ions for the cross-sectioned Si and W layers are concentrated very n ear their surfaces of < 10 nm to yield the Ga concentrations C-Ga Of a bout 4 and 9 at % for these layers, respectively. Although there is so me differences in sample materials between the calculations and the ex periments, the calculated C-Ga values for Si and W layers roughly agre e with the experimental values for the magneto-optical disk TEM sample . This agreement firmly supports the present modeling of FIB-milled cr oss sections. (C) 1998 American Vacuum Society.