END-POINT DETECTION USING ABSORBED CURRENT, SECONDARY-ELECTRON, AND SECONDARY ION SIGNALS DURING MILLING OF MULTILAYER STRUCTURES BY FOCUSED ION-BEAM

Many applications of focused ion beam micromachining of multilayer structures require the ability to accurately and unambiguously signal the transition from one layer to the next during milling. Instances where this may be critical include most microcircuit sectioning, reconfiguring, or repair operations. Here we compare absorbed specimen current with secondary electron and secondary ion signals and contrast their effectiveness in providing an indication of end-point. A number of thin film and multilayer samples have been investigated including thin films of Au and W (thickness 0.1 mum) deposited on Si, and Al (thickness 1.0 mum) deposited on thermally grown SiO2 (thickness 1.0 mum) on Si.