Proceedings Article | 1 March 2004

Proc. SPIE. 5398, Sixth Seminar on Problems of Theoretical and Applied Electron and Ion Optics

KEYWORDS: Chromatic aberrations, Lithography, Monochromatic aberrations, Lenses, Electrodes, Ions, Magnetism, Colorimetry, Objectives, Gallium

This paper is the further development of work of authors [V.A. Zhukov et. al., Proceedings of SPIE, 5128, (2003)] devoted to theoretical research of the limiting resolution or Critical Development (CD) in ion lithography at use as objectives the combined axial symmetrical immersion lenses. In the given paper the refinement of the basic critical ion-optical parameters of objective combined immersion lenses is carried out. These parameters are the coefficient of a chromatic aberration of first order Cc and the maximal density of a current in the superconducting coil of excitation of combined lens I/S depending on parameter of retardation (immersion) τ=W_{t}/W_{o}. Where W_{t} is energy of ions on a target, W is the energy of ions before a lens, I is a current, and S is area of cross section of the coil. It is shown, that in combined axial symmetrical lenses it is possible to compensate in principle as much as full a chromatic abberation of the first order C_{c} and a spherical abberation of the third order Cs, since at parametere of retardation τ → 0 also Cc, Cs →0. However, full compensation can take place only at τ=0, i.e. at a full stopping of particles.
With the help of a method of Monte Carlo the distributions of implanted Ga atoms on depth and on radial coordinate of a crystal target from silicon are calculated at falling for target surface of indefinitely thin beam of Ga^{+} ions by energy W_{t} in 1 keV. From these calculations it follows, that using ion implantation from the focused ion beams, it is possible to receive 2 x 10^{12} pixels with the size 3.6 x 3.6 nm^{2} everyone, in the frame in the size 3 x 3 mm^{2} on an ion-lithographic target.