Mini rf-driven ion sources for focused ion beam systems

Abstract

Mini rf-driven ion sources with 1.2 cm and 1.5 cm inner chamber diameter have been developed at Lawrence Berkeley National Laboratory. Several gas species have been tested including argon, krypton, and hydrogen. These mini ion sources operate in inductively coupled mode and are capable of generating high current density ion beams at tens of watts of absorbed rf power. Since the plasma potential is relatively low in the plasma chamber, these mini ion sources can function reliably without any perceptible sputtering damage of the chamber wall. The mini rf-driven ion sources will be combined with electrostatic focusing columns, and are capable of producing nanofocused ion beams for micromachining and semiconductor fabrications.

Radio frequency-driven proton source with a back-streaming electron dump

“…Different antenna configurations have been used in rfdriven ion sources: internal antenna, 1 external helical antenna, 2,3 and external planar antenna. 4 Lifetime has always been an issue for internal antenna.…”

A high brightness source for nano-probe secondary ion mass spectrometry

“…The highest performance reported by LBL [21] resulted in an Ar + current density of 220 mA/cm 2 from the source and it was concluded by extrapolation from the current density and associated brightness of the multi-cusp source characterized by Scipioni, that this source would have a reduced brightness of $2.3 Â 10 4 A m À2 sr À1 V À1 . Unfortunately, no experimentally derived brightness values have been reported by this group.…”

Ion Sources Used for Secondary Ion Mass Spectrometry

“…Although these are monatomic and cannot in any way be considered "cluster" sources, the production of these atomic ion beams is similar to and has often preceded their molecular or cluster cousins, lending conceptual notions from one to the other. These include field emission, typically from tips of a low melting point metal or metal eutectic that can form Taylor cones with slight heating and an applied field, 15 radio frequency (RF) ionization in a plasma, 16,17 electron-impact sources that are typically used to produce beams of positive ions from gases, 18 thermal ionization, 11 DC-glow discharges, 19,20 and sputtering. 21…”