[7p-C13-1~9] Recent GFIS /advanced ion source microscopy technologies and its future prospects for R & D of materials and devices

▲ [7p-C13-7] Development of scanning ion microscope with H₃⁺ gas field ionization ion source

〇Shinichi Matsubara¹, Hiroyasu Shichi¹, Tomihiro Hashizume¹ (1.Hitachi, Ltd., Research & Development Group)

Keywords:scanning ion microscopy, hydrogen ion, focused ion beam

It is well documented that three kinds of ion species (H⁺, H₂⁺, and H₃⁺) can be generated by field ionization [1]. In particular, an energy spread of H₃⁺ ions is expected to be smallest among these three ion species because of their generation process [2]. This property must be advantageous for convergence of the ion beam, but there have been a few arguments for practical use of H₃⁺ ions in scanning ion microscopy (SIM) or in the direct lithography. First, a stable ion emission of gaseous species with low ionization field, such as H⁺, H₂⁺, H₃⁺, N₂⁺, and Ar⁺, is generally difficult because of impurities migrating on the emitter tip and reaching the emission area under a relatively small electric field. Second, it has been thought that the intensity of H₃⁺ current is relatively small compared with that of H⁺ or H₂⁺. We have overcome these problems as follows. We have shown a stable H₃⁺ emission by using our own hydrogen gas purifier [3]. We have also shown that H₃⁺ current is enhanced by terminating emitter tip with one atom [3]. As a result we achieved enough H₃⁺ current with sufficient stability to take H₃⁺ SIM images in our own SIM. In addition it has been revealed that the energy distribution of H₃⁺ ions is actually narrower comparing with that of H₂⁺ ions by this equipment [4]. In this presentation, we also describe a new result on switching the hydrogen ions for imaging and the heavy ions for processing.
[1] T. C. Clements and E. W. Mueller, “Occurrence of H₃⁺ in the Field Ionization of Hydrogen,” J. Chem. Phys. 37 (1962) 2684.
[2] T. T. Tsong , “Atom-Probe Field Ion Microscopy,” Cambridge U. P. New York (1990) p. 25.
[3] S. Matsubara, H. Shichi, Y. Kawanami and H. Hashizume, “Stable H₃⁺ emission from hydrogen gas field ion source by single-atom terminated emitter tip,” HeFIB (2016) Luxembourg City.
[4] S. Matsubara, H. Shichi, Y. Kawanami and H. Hashizume, “Novel Scanning Ion Microscope with H₃⁺ Gas Field Ionization Source,” Microscopy and Microanalysis (2016), Columbus, Ohio.