Characterization and Effects of Fluorine-Containing Ionic Liquid Ion Beams on Metal-Coated Substrates*

Ionic liquid ion sources offer a versatile alternative to liquid metal ion sources, cluster ion beams, and plasma etching, providing positive and negative ions with large mass. This ability allows them to compensate substrate charging in dielectric samples by emitting current at both polarities. Their large molecular structures result in sputtering mechanisms similar to Ar_n⁺ cluster ions, while their halogen and oxygen components contribute to reactive ion etching.

In this study, we will examine 1-Ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMI-FSI), 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI), and 1-Ethyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide (EMI-PFSI) on 50 nm metal-coated silicon substrates to explore the effect of fluorine on ion beam sputtering of metals. The ions will be emitted from a porous glass emitter tip biased either positively or negatively. Using our diagnostic setup, we will identify the beam composition and energy distribution of ions, and measure emitter current. Post-etching, the milled depth of substrates will be analysed under SEM. Our goal is to provide an alternative method to etch metal interconnect layers for integrated circuits.