Anthony Graupera

Mass filtered plasma focused ion beam system

The authors describe an inductively coupled plasma ion source combined with a mass tunable Wien (E × B) filter that is capable of delivering single or mixed gas plasma generated ions. Gases for the RF powered ion source can be premixed or of variable stoichiometry by mixing individual gases. The gas mixtures can contain a variety of elements providing light to heavy gaseous ions which can be selected by mass filtering. Optimization of the plasma source consists of varying parameters such as the RF power, pressure, and gas stoichiometry. Subsequently, the mass filter/plasma-gas ion column can be optimized for a wide range of applications. For example, high resolution imaging using high reduced brightness light ions (e.g., for subsurface imaging) or fast material removal using heavy ions may be accomplished across a wide range of beam currents, typically 10 pA to 10 μA, with the same gas mixture. The authors have examined several candidate species (He+, Ne+, Ar+, Xe+, O2+, O+, O−, N+, N2+, H+, H2+, H3+) and...