ETH Zurich: High quality ion-beam generation for Mass Spectrometry or Semiconductor Applications

A novel patent pending ion source comprising laser ablation for ion generation and an ion funnel for high intensity, low emittance ion beams has been developed at ETH Zurich. The source utilizes the damping of ion motion inside a gas-filled ion funnel to generate a beam of predominantly positively charged ions from practically any solid material. Initially, ions are generated by pulsed laser ablation or laser desorption and ionization.

The quality of the ion source of any mass spectrometer, ion beam lithography or – deposition system usually determines the performance of the technique as ion transmission efficiency, beam diameter and quality of beam focus. High quality ion sources are characterized by a low normalized emittance, allowing to focus intense ion beam to sub-µm regions. Laser ablation can produce an ion beam of practically any solid material but yields broad energy distributions and high emittance of the ion beam. Guiding these primary ions through an ion funnel reduces the energy distribution and transmits ions with high efficiency. Thus the emittance of the source is dramatically improved.

Invention

Ions generated by laser ablation under moderate vacuum are introduced into an ion funnel via a specifically designed supersonic nozzle. Radio frequency-fields of alternating polarity are applied to the funnel electrodes to confine the ion beam close to its axis. At the same time collisions with a background gas reduce the translational energies and narrow the energy distribution significantly. Highly efficient ion transport through the ion funnel is ensured by an optimized gas flow directing the ions towards an aperture before the high vacuum region of the mass spectrometer or other ion beam anipulation system.

The ions exiting the funnel are characterized by a very narrow axial and radial energy distribution which allows focusing of the beam to sub-µm regions with high efficiency and without necessity of high electrostatic acceleration. The optimized gas dynamics inside the funnel render additional electrostatic potentials inside the funnel unnecessary and thus dramatically simplify construction and maintenance.

Features & Benefits

• Higher detection efficiency of any solid material
• Increased deposition and erosion rates
• Efficient ion transfer for ions of any mass / charge -ratio
• Easy replacement of the standard ion source is possible in practically any instrumentation utilizing ion beams
• Low maintenance and construction costs

Field of Application

• Mass Spectrometry - Direct analysis of the elemental and molecular content of any solid material
• Semiconductor applications - Ion deposition at high lateral resolution with high deposition rates
• High resolution ion erosion techniques or secondary ion Mass Spectrometry - Generation of high current primary ion beams for ion bombardment

For more information, contact ETH Zurich at +41 44 632 23 82 or [email protected].