LOW-ENERGY FOCUSED-ION-BEAM SHAPE OBSERVATION AND ITS NOISE-REDUCTIONFOR NANOFABRICATION

Two types of noise from the variable landing-energy focused-ion-beam ( FIB) system appeared when FIB was line-scanned on an n-GaAs wafer and implantation-induced damage was estimated by using selective etching a nd secondary electron microscope (SEM) observation. The first had a ro ugh surface with small craters away from implanted lines and the secon d had clearly observable scratchiness along implanted lines. Cathode l uminescence measurement and auger analysis were performed to estimate beam-tail spreading. Both the long-beam-tail and the scratchy noise pr obably originated from unintentionally scattered beams in the ion-beam lens column and/or neutral particles emitted from the liquid metal io n source. As a result, these noises could be greatly reduced by locati ng a new aperture at an appropriate position. Using this refined FIB s ystem, low landing-energy-ion-beams should be able to be applied to fa bricate high-quality mesoscopic devices.