Minimum feature sizes and ion beam profile for a focused ion beam system with post-objective lens retarding and acceleration mode

Abstract
The beam characteristics of a focused Ga+-ion beam (FIB) at ion energies between 10 and 150 keV have been investigated by using a 100 keV focused ion beam system with an additional post-objective lens retarding and acceleration electrode. Line structures with minimum feature sizes down to 20 nm almost independent of the landing energy of the ions could be realized by sputtering line patterns in a gold-coated GaAs substrate. The current density profile was determined over six orders of magnitude by measuring the radii of FIB-exposed dot structures as a function of the ion dose. The beam diameters have been found to be in the range between 30 and 45 nm, nearly independent of the available ion energies. The photoluminescence signal of locally intermixed AlGaAs/GaAs quantum well structures was used to study the spatial resolution of FIB-implanted line patterns. The results were compared with the lateral resolution, which can be calculated from the current density distribution of the beam profile.

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