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Foil Electron Ion-Beam Lens

IP.com Disclosure Number: IPCOM000045537D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

McCorkle, RA: AUTHOR

Abstract

In a focussed ion-beam system, the ion beam is passed through a thin metal foil after it Passes through the final focussing lens and before it strikes a target in order to electrically neutralize the beam and enable a sharper focus to be obtained at the target.

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Foil Electron Ion-Beam Lens

In a focussed ion-beam system, the ion beam is passed through a thin metal foil after it Passes through the final focussing lens and before it strikes a target in order to electrically neutralize the beam and enable a sharper focus to be obtained at the target.

The writing speed of charged-particle beams for lithography or microscopy is know to be limited by space-charge and/or the Boersch effect (1). Moreover, surface charging of targets is well-known to be a serious problem in both applications. These effects may be avoided by charge neutralizing the ion beam after it has passed through the final focussing lens.

It has been shown that ion beams may be neutralized either by the trapping of electrons (2) or through the use of the "convoy effect" (3, 4) and that the electrons within the ion beam have an electron temperature of kTe Approx. Equal 0.043(m(e)/m(i))E(i), where E(i)=ion energy, m(i)= ion mass, and m=electron mass. Thus a focussed, neutralized ion beam of diameter d(m) is obtainable from an initial beam diameter d(o) and injection angle Theta, where d(m) Approx. Equal 0.27 x 10/-3/d(o)/A/3/4 tan 3/2 Theta, where A is the mass number of the ion. Thus, a thin foil 10 (permitting low-scattering transmission of ions) placed after the final lens 12 near to the target 14 allows tight focussing of ion beam 16 uninhibited by the above-discussed limiting processes.

References
(1) W. Knauer, J. Vac. Sci. Technol. 16 (6), 1676

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