Characteristics Comparison of Neon, Argon, and Krypton Ion Emissions from Gas Field Ionization Sources with a Single-Atom Tip.

A scanning ion beam instrument equipped with a gas field ionization source (GFIS) has been commercialized, but only helium and neon are currently available as GFISs. In this study, the characteristics of neon, argon, and krypton ion emissions from a single-atom tip are compared, specifically for faster fabrication by milling of a silicon sample. Although the boiling point of argon is about 87 K, our experiments on characterizing argon ion emission can be carried out at temperatures of about 50 K at an argon gas pressure lower than 0.1 Pa. Argon exhibits ion current characteristics, as a function of tip voltage, between those of neon and krypton. The value obtained by multiplying the ion emission current by the sputtering yield is suitable for a figure of merit (FOM) for faster fabrication. The FOM for argon is the highest among the three ion species. This value must be extensively evaluated from the viewpoint of practical nano-fabrication application. The instabilities of neon, argon, and krypton ion currents (3σ) become as low as 8% in 1 h, which is sufficient for fabrication applications. We conclude that an argon or krypton GFIS ion beam instrument will be a useful tool for nano-fabrication.

A new FIB fabrication method for micropillar specimens for three-dimensional observation using scanning transmission electron microscopy.

A new method to prepare micropillar specimens with a high aspect ratio that is suitable for three-dimensional scanning transmission electron microscopy (3D-STEM) was developed. The key features of the micropillar fabrication are: first, microsampling to extract a small piece including the structure of interest in an IC chip, and second, an ion-beam with an incident direction of 60 degrees to the pillar's axis that enables the parallel sidewalls of the pillar to be produced with a high aspect ratio. A memory-cell structure (length: 6 microm; width: 300 x 500 nm) was fabricated in the micropillar and observed from various directions with a 3D-STEM. A planiform capacitor covered with granular surfaces and a solid crossing gate and metal lines was successfully observed threedimensionally at a resolution of approximately 5 nm.