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This clickable image map represents the typical biasing of the source and electrodes in a beam line that has three modes of operation, Drift, Post Accel, and Post Decel. Drift simple means that the energy of the ion beam does not increased or decreased after the analyzer magnet. Post accel refer to an increase in energy and post decel refers to a decrease in energy.
More on The Ion Source...
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The Extraction, Suppression, Ground Electrodes are used for extracting positively charged ions from the source that combine downstream to form a broad beam. Individual electrodes in close proximity to the extraction electrode can be biased to inhibit back streaming of neutralizing electrons close to the source or back to the extraction electrode.
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The Magnet A mass analyzing magnet positioned along the beam path between the source and the process chamber filters ions from the beam while allowing certain other ions to enter the process chamber. The magnet includes multiple magnet pole pieces constructed from a ferromagnetic material and having inwardly facing pole surfaces.. One or more current carrying coils set up dipole magnetic fields in the deflection region near the pole pieces. Additional coils help set up a quadruple field in deflection region.
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The following equation shows the relationship between the magnetic field (B), the ion accelerating voltage (V), the mass-to-charge ratio (m/q), and the radius of ion curvature (r) in the magnetic field. In atomic units, m/q becomes m/z where z is the number of charges on the ion.
The Post accel/decel Electrode system is used for post analysis acceleration of an ion beam to a selected final energy without beam blow-up. A group of electrodes establish a non-linear voltage gradient along the beam axis for accelerating and then decelerating the beam to the selected final energy level with focusing.
Focusing of the Ion
Beam is also provided by the construction and shape of the
electrodes. The suppression electrode produces a inner zero electrostatic
field, and an outer electrostatic on a field such that ions entering this
outer field are deflected by an amount that is a function of their distance
from the edge of the inner field. The result is a focused beam having a
uniform intensity over a given target area and at a given distance from
the lens.
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More Links...
Ion Implantation and Ion Beam Analysis
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This page is sponsored by Case
Technology Inc. since 5/1/98.
Updated 6/6/99.
