Alternative emitter substrates for Ionic Liquid Ion Source implementation in focused ion beams

Ionic Liquid Ion Sources (ILIS) are high-brightness sources with properties adequate for implementation in Focused Ion Beam Applications. ILIS are capable of producing positively or negatively charged beams of heavy and reactive ions, which could be used advantageously in applications such as lithography and localized etching. For FIB use, stable operation over lifetimes in excess of hundreds of hours must be demonstrated. In this paper, we describe an oxidation treatment for ILIS emitters that allows better wetting by the ionic liquid. This emitter is implemented with a distal electrode contact to improve its electrochemical behavior. The current-voltage responses of this configuration are presented, and coarse retarding potential analysis measurements indicate that the alternative ILIS geometry produces a beam population similar to the traditional configuration. Current measurements over prolonged tests demonstrate that the sources can operate for several hundred hours and are capable of excellent short-term stability, but random variations in the emission over hour timescales indicate that factors such as backsputtering, tip geometry and liquid contamination should be controlled to guarantee prolonged stable operation.