Micromachined multiple focused-ion-beam devices

Micromachined multiple focused-ion-beam devices were developed, which were composed of an array of ion sources, electrostatic extractors, and lenses to achieve concurrent processing of microdevices with high throughput. All of the parts of the devices were fabricated and packaged on the scale of a microchip, employing Si bulk micromachining technologies. Ionic liquids (ILs) were used to generate the ion species instead of conventional liquid metals such as Ga and In. Three types of testing devices were fabricated to comprehensively evaluate the system. The first, device 1, consisted of the emitter arrays and a biased Si target, whereby the etching characteristics of beams generated with several ILs were evaluated. The peaks of SiF⁺, SiF₂⁺, SiF₃⁺, and SiF₄⁺, which provide evidence for reactive etching of Si, were obtained by in situ monitoring of the gas composition. Compared with a conventional Ga ion source, the ion beams emitted from the IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide exhibited a 5.4-fold sputtering yield of 11.9 atom/ion at an acceleration voltage of 5 kV. In device 2, the electrostatic extractor and lens were mounted on the emitter array, and control of the divergence angle of the ion beam was confirmed. In device 3, which has a separated extractor on the electrostatic lens plate, an individual control of ion beams was demonstrated.