A LOW MAGNIFICATION FOCUSED ION-BEAM SYSTEM WITH 8 NM SPOT SIZE

A 50 keV Ga+ beam has been focused to a spot diameter of 8 nm (full width at half-maximum) in our two-lens microprobe system by reducing the contributions of both chromatic aberration and the virtual ion source size to the final image size. Features as small as 6 to 8 nm were distinctly visible in scanning ion images. To our knowledge, this is the smallest focused beam of ions produced to date. The limiting resolution in 30-nm thick films of poly(methylmethacrylate) exposed with this beam was approximately 8 to 10 nm. Effects such as ion scattering, atomic recoil, and statistical dose fluctuations during exposure are believed to set inherent limits to the lithographic resolution.